SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Johansson Roland S) "

Sökning: WFRF:(Johansson Roland S)

  • Resultat 1-50 av 75
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Akselsson, Roland, et al. (författare)
  • Multidisciplinary Research on Integration of Human Factors and Production Concepts such as TQM - A Participatory Discussion Session
  • 1999
  • Ingår i: Proceedings of the Conference on TQM and Human Factors. - 9172195207 ; 2, s. 439-448
  • Konferensbidrag (refereegranskat)abstract
    • A discussion session where the conference participants are invited to participate is planned. One topic for the session is to discuss experiences of multidisciplinary research on integration of human factors and different production concepts applied in change processes within Swedish companies. An important question that the discussion will focus on is: How to get high quality in multidisciplinary research? Another topic is to discuss how people from different disciplines in the companies interact with each other and with the researchers. Researchers from the centre Change@Work at Lund University in Sweden will present some of their experiences from several years of multidisciplinary research in companies. As a background the research questions within Change@Work are presented below. Discussions during the workshop will be performed according to methods used by the researchers in their research in the companies. All discussion will be documented and later sent to all workshop participants.
  •  
2.
  • Diamond, Jonathan S., et al. (författare)
  • Rapid Visuomotor Corrective Responses during Transport of Hand-Held Objects Incorporate Novel Object Dynamics
  • 2015
  • Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 35:29, s. 10572-10580
  • Tidskriftsartikel (refereegranskat)abstract
    • Numerous studies have shown that people are adept at learning novel object dynamics, linking applied force and motion, when performing reaching movements with hand-held objects. Here we investigated whether the control of rapid corrective arm responses, elicited in response to visual perturbations, has access to such newly acquired knowledge of object dynamics. Participants first learned to make reaching movements while grasping an object subjected to complex load forces that depended on the distance and angle of the hand from the start position. During a subsequent test phase, we examined grip and load force coordination during corrective arm movements elicited (within similar to 150 ms) in response to viewed sudden lateral shifts (1.5 cm) in target or object position. We hypothesized that, if knowledge of object dynamics is incorporated in the control of the corrective responses, grip force changes would anticipate the unusual load force changes associated with the corrective arm movements so as to support grasp stability. Indeed, we found that the participants generated grip force adjustments tightly coupled, both spatially and temporally, to the load force changes associated with the arm movement corrections. We submit that recently learned novel object dynamics are effectively integrated into sensorimotor control policies that support rapid visually driven arm corrective actions during transport of hand held objects.
  •  
3.
  • Flanagan, J R, et al. (författare)
  • Sensorimotor prediction and memory in object manipulation
  • 2001
  • Ingår i: Canadian journal of experimental psychology. - : Canadian Psychological Association. - 1196-1961 .- 1878-7290. ; 55:2, s. 87-95
  • Tidskriftsartikel (refereegranskat)abstract
    • When people lift objects of different size but equal weight, they initially employ too much force for the large object and too little force for the small object. However, over repeated lifts of the two objects, they learn to suppress the size-weight association used to estimate force requirements and appropriately scale their lifting forces to the true and equal weights of the objects. Thus, sensorimotor memory from previous lifts comes to dominate visual size information in terms of force prediction. Here we ask whether this sensorimotor memory is transient, preserved only long enough to perform the task, or more stable. After completing an initial lift series in which they lifted equally weighted large and small objects in alternation, participants then repeated the lift series after delays of 15 minutes or 24 hours. In both cases, participants retained information about the weights of the objects and used this information to predict the appropriate fingertip forces. This preserved sensorimotor memory suggests that participants acquired internal models of the size-weight stimuli that could be used for later prediction.
  •  
4.
  • Armstrong, Irene T, et al. (författare)
  • Waiting for a hand : saccadic reaction time increases in proportion to hand reaction time when reaching under a visuomotor reversal
  • 2013
  • Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media SA. - 1662-5161. ; 7, s. 319-
  • Tidskriftsartikel (refereegranskat)abstract
    • Although eye movement onset typically precedes hand movement onset when reaching to targets presented in peripheral vision, arm motor commands appear to be issued at around the same time, and possibly in advance, of eye motor commands. A fundamental question, therefore, is whether eye movement initiation is linked or yoked to hand movement. We addressed this issue by having participants reach to targets after adapting to a visuomotor reversal (or 180° rotation) between the position of the unseen hand and the position of a cursor controlled by the hand. We asked whether this reversal, which we expected to increase hand reaction time (HRT), would also increase saccadic reaction time (SRT). As predicted, when moving the cursor to targets under the reversal, HRT increased in all participants. SRT also increased in all but one participant, even though the task for the eyes-shifting gaze to the target-was unaltered by the reversal of hand position feedback. Moreover, the effects of the reversal on SRT and HRT were positively correlated across participants; those who exhibited the greatest increases in HRT also showed the greatest increases in SRT. These results indicate that the mechanisms underlying the initiation of eye and hand movements are linked. In particular, the results suggest that the initiation of an eye movement to a manual target depends, at least in part, on the specification of hand movement.
  •  
5.
  • Baugh, Lee A., et al. (författare)
  • Material evidence : interaction of well-learned priors and sensorimotor memory when lifting objects
  • 2012
  • Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 108:5, s. 1262-1269
  • Tidskriftsartikel (refereegranskat)abstract
    • Skilled object lifting requires the prediction of object weight. When lifting new objects, such prediction is based on well-learned size-weight and material-density correlations, or priors. However, if the prediction is erroneous, people quickly learn the weight of the particular object and can use this knowledge, referred to as sensorimotor memory, when lifting the object again. In the present study, we explored how sensorimotor memory, gained when lifting a given object, interacts with well-learned material-density priors when predicting the weight of a larger but otherwise similar-looking object. Different groups of participants 1st lifted 1 of 4 small objects 10 times. These included a pair of wood-filled objects and a pair of brass-filled objects where 1 of each pair was covered in a wood veneer and the other was covered in a brass veneer. All groups then lifted a larger, brass-filled object with the same covering as the small object they had lifted. For each lift, we determined the initial peak rate of change of vertical load-force rate and the load-phase duration, which provide estimates of predicted object weight. Analysis of the 10th lift of the small cube revealed no effects of surface material, indicating participants learned the appropriate forces required to lift the small cube regardless of object appearance. However, both surface material and core material of the small cube affected the 1st lift of the large block. We conclude that sensorimotor memory related to object density can contribute to weight prediction when lifting novel objects but also that long-term priors related to material properties can influence the prediction.
  •  
6.
  • Baugh, Lee A., et al. (författare)
  • Representing multiple object weights : competing priors and sensorimotor memories
  • 2016
  • Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 116:4, s. 1615-1625
  • Tidskriftsartikel (refereegranskat)abstract
    • When lifting an object, individuals scale lifting forces based on long-term priors relating external object properties (such as material and size) to object weight. When experiencing objects that are poorly predicted by priors, people rapidly form and update sensorimotor memories that can be used to predict an object's atypical size-weight relation in support of predictively scaling lift forces. With extensive experience in lifting such objects, long-term priors, assessed with weight judgments, are gradually updated. The aim of the present study was to understand the formation and updating of these memory processes. Participants lifted, over multiple days, a set of black cubes with a normal size-weight mapping and green cubes with an inverse size-weight mapping. Sensorimotor memory was assessed with lifting forces, and priors associated with the black and green cubes were assessed with the size-weight illusion (SWI). Interference was observed in terms of adaptation of the SWI, indicating that priors were not independently adjusted. Half of the participants rapidly learned to scale lift forces appropriately, whereas reduced learning was observed in the others, suggesting that individual differences may be affecting sensorimotor memory abilities. A follow-up experiment showed that lifting forces are not accurately scaled to objects when concurrently performing a visuomotor association task, suggesting that sensorimotor memory formation involves cognitive resources to instantiate the mapping between object identity and weight, potentially explaining the results of experiment 1. These results provide novel insight into the formation and updating of sensorimotor memories and provide support for the independent adjustment of sensorimotor memory and priors.
  •  
7.
  • Bengtsson, Fredrik, et al. (författare)
  • Integration of sensory quanta in cuneate nucleus neurons in vivo
  • 2013
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2, s. e56630-
  • Tidskriftsartikel (refereegranskat)abstract
    • Discriminative touch relies on afferent information carried to the central nervous system by action potentials (spikes) in ensembles of primary afferents bundled in peripheral nerves. These sensory quanta are first processed by the cuneate nucleus before the afferent information is transmitted to brain networks serving specific perceptual and sensorimotor functions. Here we report data on the integration of primary afferent synaptic inputs obtained with in vivo whole cell patch clamp recordings from the neurons of this nucleus. We find that the synaptic integration in individual cuneate neurons is dominated by 4-8 primary afferent inputs with large synaptic weights. In a simulation we show that the arrangement with a low number of primary afferent inputs can maximize transfer over the cuneate nucleus of information encoded in the spatiotemporal patterns of spikes generated when a human fingertip contact objects. Hence, the observed distributions of synaptic weights support high fidelity transfer of signals from ensembles of tactile afferents. Various anatomical estimates suggest that a cuneate neuron may receive hundreds of primary afferents rather than 4-8. Therefore, we discuss the possibility that adaptation of synaptic weight distribution, possibly involving silent synapses, may function to maximize information transfer in somatosensory pathways.
  •  
8.
  •  
9.
  • Birznieks, Ingvars, et al. (författare)
  • Encoding of direction of fingertip forces by human tactile afferents
  • 2001
  • Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 21:20, s. 8222-8237
  • Tidskriftsartikel (refereegranskat)abstract
    • In most manipulations, we use our fingertips to apply time-varying forces to the target object in controlled directions. Here we used microneurography to assess how single tactile afferents encode the direction of fingertip forces at magnitudes, rates, and directions comparable to those arising in everyday manipulations. Using a flat stimulus surface, we applied forces to a standard site on the fingertip while recording impulse activity in 196 tactile afferents with receptive fields distributed over the entire terminal phalanx. Forces were applied in one of five directions: normal force and forces at a 20 degrees angle from the normal in the radial, distal, ulnar, or proximal directions. Nearly all afferents responded, and the responses in most slowly adapting (SA)-I, SA-II, and fast adapting (FA)-I afferents were broadly tuned to a preferred direction of force. Among afferents of each type, the preferred directions were distributed in all angular directions with reference to the stimulation site, but not uniformly. The SA-I population was biased for tangential force components in the distal direction, the SA-II population was biased in the proximal direction, and the FA-I population was biased in the proximal and radial directions. Anisotropic mechanical properties of the fingertip and the spatial relationship between the receptive field center of the afferent and the stimulus site appeared to influence the preferred direction in a manner dependent on afferent type. We conclude that tactile afferents from the whole terminal phalanx potentially contribute to the encoding of direction of fingertip forces similar to those that occur when subjects manipulate objects under natural conditions.
  •  
10.
  • Birznieks, Ingvars, et al. (författare)
  • Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation.
  • 1998
  • Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 80:4, s. 1989-2002
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies on adaptation of fingertip forces to local friction at individual digit-object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces increased at both fingers. Thus to independently adapt fingertip forces to the local friction the normal forces were controlled at an interdigital level by using sensory information from both engaged digits. Furthermore, subjects used both short- and long-term anticipatory mechanisms in a manner consistent with the notion that the central nervous system (CNS) entertains internal models of relevant object and task properties during manipulation.
  •  
11.
  •  
12.
  • Birznieks, Ingvars, et al. (författare)
  • Slowly adapting mechanoreceptors in the borders of the human fingernail encode fingertip forces
  • 2009
  • Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 29:29, s. 9370-9379
  • Tidskriftsartikel (refereegranskat)abstract
    • There are clusters of slowly adapting (SA) mechanoreceptors in the skin folds bordering the nail. These "SA-IInail" afferents, which constitute nearly one fifth of the tactile afferents innervating the fingertip, possess the general discharge characteristics of slowly adapting type II (SA-II) tactile afferents located elsewhere in the glabrous skin of the human hand. Little is known about the signals in the SA-IInail afferents when the fingertips interact with objects. Here we show that SA-IInail afferents reliably respond to fingertip forces comparable to those arising in everyday manipulations. Using a flat stimulus surface, we applied forces to the finger pad while recording impulse activity in 17 SA-IInail afferents. Ramp-and-hold forces (amplitude 4 N, rate 10 N/s) were applied normal to the skin, and at 10, 20, or 30 degrees from the normal in eight radial directions with reference to the primary site of contact (25 force directions in total). All afferents responded to the force stimuli, and the responsiveness of all but one afferents was broadly tuned to a preferred direction of force. The preferred directions among afferents were distributed all around the angular space, suggesting that the population of SA-IInail afferents could encode force direction. We conclude that signals in the population of SA-IInail afferents terminating in the nail walls contain vectorial information about fingertip forces. The particular tactile features of contacted surfaces would less influence force-related signals in SA-IInail afferents than force-related signals present in afferents terminating in the volar skin areas that directly contact objects.
  •  
13.
  • Bowman, Miles C, et al. (författare)
  • Eye-hand coordination in a sequential target contact task
  • 2009
  • Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 195:2, s. 273-283
  • Tidskriftsartikel (refereegranskat)abstract
    • Most object manipulation tasks involve a series of actions demarcated by mechanical contact events, and gaze is typically directed to the locations of these events as the task unfolds. Here, we examined the timing of gaze shifts relative to hand movements in a task in which participants used a handle to contact sequentially five virtual objects located in a horizontal plane. This task was performed both with and without visual feedback of the handle position. We were primarily interested in whether gaze shifts, which in our task shifted from a given object to the next about 100 ms after contact, were predictive or triggered by tactile feedback related to contact. To examine this issue, we included occasional catch contacts where forces simulating contact between the handle and object were removed. In most cases, removing force did not alter the timing of gaze shifts irrespective of whether or not vision of handle position was present. However, in about 30% of the catch contacts, gaze shifts were delayed. This percentage corresponded to the fraction of contacts with force feedback in which gaze shifted more than 130 ms after contact. We conclude that gaze shifts are predictively controlled but timed so that the hand actions around the time of contact are captured in central vision. Furthermore, a mismatch between the expected and actual tactile information related to the contact can lead to a reorganization of gaze behavior for gaze shifts executed greater than 130 ms after a contact event.
  •  
14.
  • Brasselet, Romain, et al. (författare)
  • Isometric coding of spiking haptic signals by peripheral somatosensory neurons
  • 2011
  • Ingår i: Advances in Computational Intelligence. - Berlin : Springer Berlin/Heidelberg. - 9783642215018 ; , s. 528-536
  • Konferensbidrag (refereegranskat)abstract
    • We study how primary tactile afferents encode relevant contact features to mediate early processing of haptic information. In this paper, we apply metrical information theory to perform temporal decoding of human microneurography data. First, we enrich the theory by deriving a novel spike train metrics inspired by neuronal computation. This spike train metrics can be interpreted biologically and its behaviour is not influenced by spontaneous activity, which decreases the ability of other spike metrics to separate input patterns. Second, we employ our metrical information tools to demonstrate that primary spiking signals allow a putative neural decoder to go beyond stimulus discrimination. They transmit information about geometrical properties of the input space. We show that first-spike latencies are enough to guarantee maximum information transmission of tactile stimuli. However, entire primary spike trains are necessary to encode isometric representations of the stimulus space, a likely basis for generalisation in haptic perception.
  •  
15.
  • Brasselet, Romain, et al. (författare)
  • Quantifying neurotransmission reliability through metrics-based information analysis
  • 2011
  • Ingår i: Neural Computation. - 0899-7667 .- 1530-888X. ; 23:4, s. 852-881
  • Tidskriftsartikel (refereegranskat)abstract
    • We set forth an information-theoretical measure to quantify neurotransmission reliability while taking into full account the metrical properties of the spike train space. This parametric information analysis relies on similarity measures induced by the metrical relations between neural responses as spikes flow in. Thus, in order to assess the entropy, the conditional entropy, and the overall information transfer, this method does not require any a priori decoding algorithm to partition the space into equivalence classes. It therefore allows the optimal parameters of a class of distances to be determined with respect to information transmission. To validate the proposed information-theoretical approach, we study precise temporal decoding of human somatosensory signals recorded using microneurography experiments. For this analysis, we employ a similarity measure based on the Victor-Purpura spike train metrics. We show that with appropriate parameters of this distance, the relative spike times of the mechanoreceptors? responses convey enough information to perform optimal discrimination?defined as maximum metrical information and zero conditional entropy?of 81 distinct stimuli within 40 ms of the first afferent spike. The proposed information-theoretical measure proves to be a suitable generalization of Shannon mutual information in order to consider the metrics of temporal codes explicitly. It allows neurotransmission reliability to be assessed in the presence of large spike train spaces (e.g., neural population codes) with high temporal precision.
  •  
16.
  • Burstedt, Magnus K, et al. (författare)
  • Control of forces applied by individual fingers engaged in restraint of an active object.
  • 1997
  • Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 78:1, s. 117-128
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated the coordination of fingertip forces in subjects who used the tips of two fingers to restrain an instrumented manipulandum with horizontally oriented grip surfaces. The grip surfaces were subjected to tangential pulling forces in the distal direction in relation to the fingers. The subjects used either the right index and middle fingers (unimanual grasp) or both index fingers (bimanual grasp) to restrain the manipulandum. To change the frictional condition at the digit-object interfaces, either both grip surfaces were covered with sandpaper or one was covered with sandpaper and the other with rayon. The forces applied normally and tangentially to the grip surfaces were measured separately at each plate along with the position of the plates. Subjects could have performed the present task successfully with many different force distributions between the digits. However, they partitioned the load in a manner that reflected the frictional condition at the local digit-object interfaces. When both digits contacted sandpaper, they typically partitioned the load symmetrically, but when one digit made contact with rayon and the other with sandpaper, the digit contacting the less slippery material (sandpaper) took up a larger part of the load. The normal forces were also influenced by the frictional condition, but they reflected the average friction at the two contact sites rather than the local friction. That is, when friction was low at one of the digit-object interfaces, only the applied normal forces increased at both digits. Thus sensory information related to the local frictional condition at the respective digit-object interfaces controlled the normal force at both digits. The normal:tangential force ratio at each digit appeared to be a controlled variable. It was adjusted independently at each digit to the minimum ratio required to prevent frictional slippage, keeping an adequate safety margin against slippage. This was accomplished by the scaling of the normal forces to the average friction and by partitioning of the load according to frictional differences between the digit-object interfaces. In conclusion, by adjusting the normal:tangential force ratios to the local frictional condition, subjects avoided excessive normal forces at the individual digit-object interfaces, and by partitioning the load according the frictional difference, subjects avoided high normal forces. Thus the local frictional condition at the separate digit-object interfaces is one factor that can strongly influence the distribution of forces across digits engaged in a manipulative act.
  •  
17.
  • Burstedt, Magnus K, et al. (författare)
  • Coordination of fingertip forces during human manipulation can emerge from independent neural networks controlling each engaged digit.
  • 1997
  • Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 117:1, s. 67-79
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated the coordination of fingertip forces in subjects who lifted an object (i) using the index finger and thumb of their right hand, (ii) using their left and right index fingers, and (iii) cooperatively with another subject using the right index finger. The forces applied normal and tangential to the two parallel grip surfaces of the test object and the vertical movement of the object were recorded. The friction between the object and the digits was varied independently at each surface between blocks of trials by changing the materials covering the grip surfaces. The object's weight and surface materials were held constant across consecutive trials. The performance was remarkably similar whether the task was shared by two subjects or carried out unimanually or bimanually by a single subject. The local friction was the main factor determining the normal:tangential force ratio employed at each digit-object interface. Irrespective of grasp configuration, the subjects adapted the force ratios to the local frictional conditions such that they maintained adequate safety margins against slips at each of the engaged digits during the various phases of the lifting task. Importantly, the observed force adjustments were not obligatory mechanical consequences of the task. In all three grasp configurations an incidental slip at one of the digits elicited a normal force increase at both engaged digits such that the normal:tangential force ratio was restored at the non-slipping digit and increased at the slipping digit. The initial development of the fingertip forces prior to object lift-off revealed that the subjects employed digit-specific anticipatory mechanisms using weight and frictional experiences in the previous trial. Because grasp stability was accomplished in a similar manner whether the task was carried out by one subject or cooperatively by two subjects, it was concluded that anticipatory adjustments of the fingertip forces can emerge from the action of anatomically independent neural networks controlling each engaged digit. In contrast, important aspects of the temporal coordination of the digits was organized by a "higher level" sensory-based control that influenced both digits. In lifts by single subjects this control was mast probably based on tactile and visual input and on communication between neural control mechanisms associated with each digit. In the two-subject grasp configuration this synchronization information was based on auditory and visual cues.
  •  
18.
  • Edin, Benoni B, et al. (författare)
  • Independent control of human finger-tip forces at individual digits during precision lifting.
  • 1992
  • Ingår i: Journal of Physiology. - 0022-3751 .- 1469-7793. ; 450, s. 547-64
  • Tidskriftsartikel (refereegranskat)abstract
    • 1. Subjects lifted an object with two parallel vertical grip surfaces and a low centre of gravity using the precision grip between the tips of the thumb and index finger. The friction between the object and the digits was varied independently at each digit by changing the contact surfaces between lifts. 2. With equal frictional conditions at the two grip surfaces, the finger-tip forces were about equal at the two digits, i.e. similar vertical lifting forces and grip forces were used. With different frictions, the digit touching the most slippery surface exerted less vertical lifting force than the digit in contact with the rougher surface. Thus, the safety margins against slips were similar at the two digits whether they made contact with surfaces of similar or different friction. 3. During digital nerve block, large and variable safety margins were employed, i.e. the finger-tip forces did not reflect the surface conditions. Slips occurred more frequently than under normal conditions (14% of all trials with nerve block, <5% during normal conditions), and they only occasionally elicited compensatory adjustments of the finger-tip forces and then at prolonged latencies. 4. The partitioning of the vertical lifting force between the digits was thus dependent on digital afferent inputs and resulted from active automatic regulation and not just from the mechanics of the task. 5. The safety margin employed at a particular digit was mainly determined by the frictional conditions encountered by the digit, and to a lesser degree by the surface condition at the same digit in the previous lift (anticipatory control), but was barely influenced by the surface condition at the other digit. 6. It was concluded that the finger-tip forces were independently controlled for each digit according to a 'non-slip strategy'. The findings suggest that the force distribution among the digits represents a digit-specific lower-level neural control establishing a stable grasp. This control relies on digit-specific afferent inputs and somatosensory memory information. It is apparently subordinated to a higher-level control that is related to the total vertical lifting and normal forces required by the lifting task and the relevant physical properties of the manipulated object.
  •  
19.
  • Ehrsson, H Henrik, et al. (författare)
  • Evidence for the involvement of the posterior parietal cortex in coordination of fingertip forces for grasp stability in manipulation
  • 2003
  • Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 90:5, s. 2978-2986
  • Tidskriftsartikel (refereegranskat)abstract
    • Grasp stability during object manipulation is achieved by the grip forces applied normal to the grasped surfaces increasing and decreasing in phase with increases and decreases of destabilizing load forces applied tangential to the grasped surfaces. This force coordination requires that the CNS anticipates the grip forces that match the requirements imposed by the self-generated load forces. Here, we use functional MRI (fMRI) to study neural correlates of the grip-load force coordination in a grip-load force task in which six healthy humans attempted to lift an immovable test object held between the tips of the right index finger and thumb. The recorded brain activity was compared with the brain activity obtained in two control tasks in which the same pair of digits generated forces with similar time courses and magnitudes; i.e., a grip force task where the subjects only pinched the object and did not apply load forces, and a load force task, in which the subjects applied vertical forces to the object without generating grip forces. Thus neither the load force task nor the grip force task involved coordinated grip-load forces, but together they involved the same grip force and load force output. We found that the grip-load force task was specifically associated with activation of a section of the right intraparietal cortex, which is the first evidence for involvement of the posterior parietal cortex in the sensorimotor control of coordinated grip and load forces in manipulation. We suggest that this area might represents a node in the network of cortical and subcortical regions that implement anticipatory control of fingertip forces for grasp stability.
  •  
20.
  • Flanagan, J Randall, et al. (författare)
  • Action plans used in action observation
  • 2003
  • Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 424:6950, s. 769-771
  • Tidskriftsartikel (refereegranskat)abstract
    • How do we understand the actions of others? According to the direct matching hypothesis, action understanding results from a mechanism that maps an observed action onto motor representations of that action. Although supported by neurophysiological and brain-imaging studies, direct evidence for this hypothesis is sparse. In visually guided actions, task-specific proactive eye movements are crucial for planning and control. Because the eyes are free to move when observing such actions, the direct matching hypothesis predicts that subjects should produce eye movements similar to those produced when they perform the tasks. If an observer analyses action through purely visual means, however, eye movements will be linked reactively to the observed action. Here we show that when subjects observe a block stacking task, the coordination between their gaze and the actor's hand is predictive, rather than reactive, and is highly similar to the gaze-hand coordination when they perform the task themselves. These results indicate that during action observation subjects implement eye motor programs directed by motor representations of manual actions and thus provide strong evidence for the direct matching hypothesis.
  •  
21.
  • Flanagan, J Randall, et al. (författare)
  • Experience can change distinct size-weight priors engaged in lifting objects and judging their weights.
  • 2008
  • Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 18:22, s. 1742-7
  • Tidskriftsartikel (refereegranskat)abstract
    • The expectation that object weight increases with size guides the control of manipulatory actions [1-6] and also influences weight perception. Thus, the size-weight illusion, whereby people perceive the smaller of two equally weighted objects to be heavier, is thought to arise because weight is judged relative to expected weight that, for a given family of objects, increases with size [2, 7]. Here, we show that the fundamental expectation that weight increases with size can be altered by experience and neither is hard-wired nor becomes crystallized during development. We demonstrate that multiday practice in lifting a set of blocks whose color and texture are the same and whose weights vary inversely with volume gradually attenuates and ultimately inverts the size-weight illusion tested with similar blocks. We also show that in contrast to this gradual change in the size-weight illusion, the sensorimotor system rapidly learns to predict the inverted object weights, as revealed by lift forces. Thus, our results indicate that distinct adaptive size-weight maps, or priors, underlie weight predictions made in lifting objects and in judging their weights. We suggest that size-weight priors that influence weight perception change slowly because they are based on entire families of objects. Size-weight priors supporting action are more flexible, and adapt more rapidly, because they are tuned to specific objects and their current state.
  •  
22.
  • Flanagan, J Randall, et al. (författare)
  • Gaze behavior when reaching to remembered targets.
  • 2008
  • Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 100:3, s. 1533-43
  • Tidskriftsartikel (refereegranskat)abstract
    • People naturally direct their gaze to visible hand movement goals. Doing so improves reach accuracy through use of signals related to gaze position and visual feedback of the hand. Here, we studied where people naturally look when acting on remembered target locations. Four targets were presented on a screen, in peripheral vision, while participants fixed a central cross (encoding phase). Four seconds later, participants used a pen to mark the remembered locations while free to look wherever they wished (recall phase). Visual references, including the screen and the cross, were present throughout. During recall, participants neither looked at the marked locations nor prevented eye movements. Instead, gaze behavior was erratic and was comprised of gaze shifts loosely coupled in time and space with hand movements. To examine whether eye and hand movements during encoding affected gaze behavior during recall, in additional encoding conditions, participants marked the visible targets with either free gaze or with central cross fixation or just looked at the targets. All encoding conditions yielded similar erratic gaze behavior during recall. Furthermore, encoding mode did not influence recall performance, suggesting that participants, during recall, did not exploit sensorimotor memories related to hand and gaze movements during encoding. Finally, we recorded a similar lose coupling between hand and eye movements during an object manipulation task performed in darkness after participants had viewed the task environment. We conclude that acting on remembered versus visible targets can engage fundamentally different control strategies, with gaze largely decoupled from movement goals during memory-guided actions.
  •  
23.
  • Flanagan, J Randall, et al. (författare)
  • Prediction precedes control in motor learning
  • 2003
  • Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 13:2, s. 146-150, Article Number: PII S0960-9822(03)00007-1
  • Tidskriftsartikel (refereegranskat)abstract
    • Skilled motor behavior relies on the brain learning both to control the body and predict the consequences of this control. Prediction turns motor commands into expected sensory consequences, whereas control turns desired consequences into motor commands. To capture this symmetry, the neural processes underlying prediction and control are termed the forward and inverse internal models, respectively. Here, we investigate how these two fundamental processes are related during motor learning. We used an object manipulation task in which subjects learned to move a hand-held object with novel dynamic properties along a prescribed path. We independently and simultaneously measured subjects' ability to control their actions and to predict their consequences. We found different time courses for predictor and controller learning, with prediction being learned far more rapidly than control. In early stages of manipulating the object, subjects could predict the consequences of their actions, as measured by the grip force they used to grasp the object, but could not generate appropriate actions for control, as measured by their hand trajectory. As predicted by several recent theoretical models of sensorimotor control, our results indicate that people can learn to predict the consequences of their actions before they can learn to control their actions.
  •  
24.
  • Flanagan, J Randall, et al. (författare)
  • Predictive mechanisms and object representations used in object manipulation
  • 2009
  • Ingår i: Sensorimotor Control of Grasping. - Cambridge : Cambridge University Press. - 9780521881579 ; , s. 161-177
  • Bokkapitel (populärvet., debatt m.m.)abstract
    • Skilled object manipulation requires the ability to estimate, in advance, the motor commands needed to achieve desired sensory outcomes and the ability to predict the sensory consequences of the motor commands. Because the mapping between motor commands and sensory outcomes depends on the physical properties of grasped objects, the motor system may store and access internal models of objects in order to estimate motor commands and predict sensory consequences. In this chapter, we outline evidence for internal models and discuss their role in object manipulation tasks. We also consider the relationship between internal models of objects employedby the sensorimotor system and representations of the same objects used by the perceptual system to make judgments about objects.
  •  
25.
  • Flanagan, J Randall, et al. (författare)
  • The role of observers' gaze behaviour when watching object manipulation tasks : predicting and evaluating the consequences of action
  • 2013
  • Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 368:1628, s. 20130063-
  • Tidskriftsartikel (refereegranskat)abstract
    • When watching an actor manipulate objects, observers, like the actor, naturally direct their gaze to each object as the hand approaches and typically maintain gaze on the object until the hand departs. Here, we probed the function of observers' eye movements, focusing on two possibilities: (i) that observers' gaze behaviour arises from processes involved in the prediction of the target object of the actor's reaching movement and (ii) that this gaze behaviour supports the evaluation of mechanical events that arise from interactions between the actor's hand and objects. Observers watched an actor reach for and lift one of two presented objects. The observers' task was either to predict the target object or judge its weight. Proactive gaze behaviour, similar to that seen in self-guided action-observation, was seen in the weight judgement task, which requires evaluating mechanical events associated with lifting, but not in the target prediction task. We submit that an important function of gaze behaviour in self-guided action observation is the evaluation of mechanical events associated with interactions between the hand and object. By comparing predicted and actual mechanical events, observers, like actors, can gain knowledge about the world, including information about objects they may subsequently act upon.
  •  
26.
  • Galván, Ignacio Fdez., et al. (författare)
  • OpenMolcas : From Source Code to Insight
  • 2019
  • Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 15:11, s. 5925-5964
  • Tidskriftsartikel (refereegranskat)abstract
    • In this Article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the new software development platform. This is followed by brief presentations of many new methods, implementations, and features of the OpenMolcas program suite. These developments include novel wave function methods such as stochastic complete active space self-consistent field, density matrix renormalization group (DMRG) methods, and hybrid multiconfigurational wave function and density functional theory models. Some of these implementations include an array of additional options and functionalities. The paper proceeds and describes developments related to explorations of potential energy surfaces. Here we present methods for the optimization of conical intersections, the simulation of adiabatic and nonadiabatic molecular dynamics, and interfaces to tools for semiclassical and quantum mechanical nuclear dynamics. Furthermore, the Article describes features unique to simulations of spectroscopic and magnetic phenomena such as the exact semiclassical description of the interaction between light and matter, various X-ray processes, magnetic circular dichroism, and properties. Finally, the paper describes a number of built-in and add-on features to support the OpenMolcas platform with postcalculation analysis and visualization, a multiscale simulation option using frozen-density embedding theory, and new electronic and muonic basis sets.
  •  
27.
  • Grigoriadis, Anastasios, et al. (författare)
  • Adaptability of mastication in people with implant-supported bridges
  • 2011
  • Ingår i: Journal of Clinical Periodontology. - 0303-6979 .- 1600-051X. ; 38:4, s. 395-404
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: We aimed to determine whether people with implant-supported bridges in both jaws, thus lacking periodontal receptors, adjust jaw muscle activity to food hardness during mastication.Materials and Methods: Thirteen participants with implant-supported bridges in both jaws and 13 with natural dentition chewed and swallowed soft and hard gelatine-based model foods, while electromyographic (EMG) activity of the masseter and temporal muscles was recorded bilaterally together with the position of the mandible. Data were compared by using a mixed-design anova model and a P-value<0.05 was considered statistically significant.Results: The number of chewing cycles and the duration of the masticatory sequence increased with food hardness in both groups, whereas vertical and lateral amplitude of the jaw movements, and the jaw-opening velocity, increased significantly with food hardness only for the dentate group. Although both groups adapted the EMG activity to the hardness of the food, the implant participants showed a significantly weaker increase in EMG activity with increased food hardness early during the masticatory sequence than the dentate participants did. In addition, the implant group showed significantly less reduction of muscle activity during the progression of the masticatory sequence than the dentate group.Conclusions: People with implant-supported bridges show an impaired adaptation of the muscle activity to food hardness during mastication. We suggest that a lack of sensory signals from periodontal mechanoreceptors accounts for the impairment.
  •  
28.
  • Grigoriadis, A, et al. (författare)
  • Temporal profile and amplitude of human masseter muscle activity is adapted to food properties during individual chewing cycles
  • 2014
  • Ingår i: Journal of Oral Rehabilitation. - : Wiley-Blackwell. - 1365-2842 .- 0305-182X. ; 41:5, s. 367-373
  • Tidskriftsartikel (refereegranskat)abstract
    • Jaw actions adapt to the changing properties of food that occur during a masticatory sequence. In the present study, we investigated how the time-varying activation profile of the masseter muscle changes during natural chewing in humans and how food hardness affects the profile. We recorded surface electromyography (EMG) of the masseter muscle together with the movement of the lower jaw in 14 healthy young adults (mean age 22) when chewing gelatin-based model food of two different hardness. The muscle activity and the jaw kinematics were analysed for different phases of the chewing cycles. The increase in the excitatory drive of the masseter muscle was biphasic during the jaw-closing phase showing early and late components. The transition between these components occurred approximately at the time of tooth-food contact. During the masticatory sequence, when the food was particularised, the size of the early component as well as the peak amplitude of the EMG significantly decreased along with a reduction in the duration of the jaw-closing phase. Except for amplitude scaling, food hardness did not appreciably affect the muscle's activation profile. In conclusion, when chewing food during natural conditions, masseter muscle activation adapted throughout the masticatory sequence, principally during the jaw-closing phase and influenced both early and late muscle activation components. Furthermore, the adaptation of jaw actions to food hardness was affected by amplitude scaling of the magnitude of the muscle activity throughout the masticatory sequence.
  •  
29.
  • Häger-Ross, Charlotte, et al. (författare)
  • Grip-force responses to unanticipated object loading : load direction reveals body- and gravity-referenced intrinsic task variables
  • 1996
  • Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 110:1, s. 142-150
  • Tidskriftsartikel (refereegranskat)abstract
    • Humans preserve grasp stability by automatically regulating the grip forces when loads are applied tangentially to the grip surfaces of a manipulandum held in a precision grip. The effects of the direction of the load force in relation to the palm, trunk, and gravity were investigated in blindfolded subjects. Controlled, tangential load-forces were delivered in an unpredictable manner to the grip surface in contact with the index finger either in the distal and proximal directions (away from and toward the palm) or in the ulnar and radial directions (transverse to the palm). The hand was oriented in: (1) a standard position, with the forearm extended horizontally and anteriorly in intermediate pronosupination; (2) an inverted position, reversing the direction of radial and ulnar loads in relation to gravity; and (3) a horizontally rotated position, in which distal loads were directed toward the trunk. The amplitude of the grip-force responses (perpendicular to the grip surface) varied with the direction of load in a manner reflecting frictional anisotropies at the digit-object interface; that is, the subjects automatically scaled the grip responses to provide similar safety margins against frictional slips. For all hand positions, the time from onset of load increase to start of the grip-force increase was shorter for distal loads, which tended to pull the object out of the hand, than for proximal loads. Furthermore, this latency was shorter for loads in the direction of gravity, regardless of hand position. Thus, shorter latencies were observed when frictional forces alone opposed the load, while longer latencies occurred when gravity also opposed the load or when the more proximal parts of the digits and palm were positioned in the path of the load. These latency effects were due to different processing delays in the central nervous system and may reflect the preparation of a default response in certain critical directions. The response to loads in other directions would incur delays required to implement a new frictional scaling and a different muscle activation pattern to counteract the load forces. We conclude that load direction, referenced to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp on objects subjected to unpredictable load forces. In contrast, the grip-force safety margin against frictional slips did not vary systematically with respect to these task variables. Instead, the magnitude of the grip-force responses varied across load direction and hand orientation according to frictional differences providing similar safety margins supporting grasp stability.
  •  
30.
  • Häger-Ross, Charlotte, et al. (författare)
  • Nondigital afferent input in reactive control of fingertip forces during precision grip
  • 1996
  • Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 110:1, s. 131-141
  • Tidskriftsartikel (refereegranskat)abstract
    • Sensory inputs from the digits are important in initiating and scaling automatic reactive grip responses that help prevent frictional slips when grasped objects are subjected to destabilizing load forces. In the present study we analyzed the contribution to grip-force control from mechanoreceptors located proximal to the digits when subjects held a small manipulandum between the tips of the thumb and index finger. Loads of various controlled amplitudes and rates were delivered tangential to the grip surfaces at unpredictable times. Grip forces (normal to the grip surfaces) and the position of the manipulandum were recorded. In addition, movements of hand and arm segments were assessed by recording the position of markers placed at critical points. Subjects performed test series during normal digital sensibility and during local anesthesia of the index finger and thumb. To grade the size of movements of tissues proximal to the digits caused by the loadings, three different conditions of arm and hand support were used; (1) in the hand-support condition the subjects used the three ulnar fingers to grasp a vertical dowel support and the forearm was supported in a vacuum cast; (2) in the forearm-support condition only the forearm was supported; finally, (3) in the no-support condition the arm was free. With normal digital sensibility the size of the movements proximal to the digits had small effects on the grip-force control. In contrast, the grip control was markedly influenced by the extent of such movements during digital anesthesia. The poorest control was observed in the hand-support condition, allowing essentially only digital movements. The grip responses were either absent or attenuated, with greatly prolonged onset latencies. In the forearm and no-support conditions, when marked wrist movements took place, both the frequency and the strength of grip-force responses were higher, and the grip response latencies were shorter. However, the performance never approached normal. It is concluded that sensory inputs from the digits are dominant in reactive grip control. However, nondigital sensory input may be used for some grip control during impaired digital sensibility. Furthermore, the quality of the control during impaired sensibility depends on the extent of movements evoked by the load in the distal, unanesthetized parts of the arm. The origin of these useful sensory signals is discussed.
  •  
31.
  • Häger Ross, Charlotte, 1962- (författare)
  • To grip and not to slip : sensorimotor mechanisms in reactive control of grasp stability
  • 1995
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The reactive control of fingertip forces maintaining grasp stability was examined in man during a prehensile task. Blindfolded subjects used the precision grip between the tips of index finger and thumb to restrain an object that was subjected to unpredictable load forces. These were delivered tangential to the parallel grip surfaces of the object. Load forces, grip forces (perpendicular to the grip surfaces) and position of the object were recorded.Subjects automatically adjusted the grip forces to loads of various amplitudes and rates. Thereby they maintained a reliable safety margin against frictional slips without using excessive grip forces. A rapid rise in grip force lasting about 0.2 s was triggered after a short delay following the onset of a sustained ramp load increase. This 'catch-up' response caused a quick restoration of an adequate grip:load force ratio that prevented frictional slips. If the ramp load continued to increase after the catchup response, the grip force also increased in parallel with the load change in a 'tracking' manner. Consequently, during the hold phases of 'ramp-and-hold' loads, the employed grip forces were approximately proportional to the load amplitude. Sensory information about the rate of change of the load force parametrically scaled the 'catchup' and 'tracking' responses.Following anesthetic block of sensory input from the digits, the grip responses were both delayed and attenuated or even abolished. To compensate for these impairments, subjects had to voluntarily maintain exceedingly high grip forces to prevent the object from slipping. The grip control improved slightly during hand and forearm support conditions that allowed marked wrist movements to occur in response to the loading. This indicates that signals from receptors in muscles, joints or skin areas proximal to the digits can to some extent be used to adjust grip forces during impaired digital sensibility. In contrast, these signals had only minor influence on the control during normal digital sensibility.Grip responses to loads delivered in various directions revealed that the load direction, in relation to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp. The load direction influenced both the response latencies and the magnitudes of the grip responses. The response latencies were shortest for loads in directions that were the most critical with regard to the consequences of frictional slippage, i.e., loads directed away from the palm or in the direction of gravity. Recordings of signals in cutaneous afferents innervating the finger tips demonstrated that these effects on the response latencies depended on differences in the time needed by the central nervous system to implement the motor responses. The short latencies in the most ‘criticar load directions may reflect the preparation of a default response, while additional central processing would be needed to execute the response to loads in other directions. Adjustments to local frictional anisotropies at the digit-object interface largely explained the magnitude effects.In conclusion, grip responses are automatically adjusted to the current loading condition during unpredictable loading of a hand held object. Subjects call up a previously acquired sensorimotor transform that supports grasp stability by preventing both object slippage and excessive grip forces. Cutaneous sensory information about tangential forces and frictional conditions at the digit-object interface is used to initiate and scale the grip responses to the current loading conditions, largely in a predictive manner.
  •  
32.
  • Jarocka, Ewa, et al. (författare)
  • Human touch receptors are sensitive to spatial details on the scale of single fingerprint ridges
  • 2021
  • Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 41:16, s. 3622-3634
  • Tidskriftsartikel (refereegranskat)abstract
    • Fast-adapting type 1 (FA-1) and slowly-adapting type 1 (SA-1) first-order tactile neurons provide detailed spatiotemporal tactile information when we touch objects with fingertips. The distal axon of these neuron types branches in the skin and innervates many receptor organs associated with fingerprint ridges (Meissner corpuscles and Merkel cell neurite complexes, respectively), resulting in heterogeneous receptive fields whose sensitivity topography includes many highly sensitive zones or "subfields." In experiments on humans of both sexes, using raised dots that tangentially scanned the receptive field we examined the spatial acuity of the subfields of FA-1 and SA-1 neurons and its constancy across scanning speed and direction. We report that the sensitivity of the subfield arrangement for both neuron types on average corresponds to a spatial period of ;0.4 mm and provide evidence that a subfield's spatial selectivity arises because its associated receptor organ measures mechanical events limited to a single papillary ridge. Accordingly, the sensitivity topography of a neuron's receptive fields is quite stable over repeated mappings and over scanning speeds representative of real-world hand use. The sensitivity topography is substantially conserved also for different scanning directions, but the subfields can be relatively displaced by directiondependent shear deformations of the skin surface.
  •  
33.
  •  
34.
  • Johansson, Roland S, et al. (författare)
  • Coding and use of tactile signals from the fingertips in object manipulation tasks
  • 2009
  • Ingår i: Nature Reviews Neuroscience. - : Springer Science and Business Media LLC. - 1471-003X .- 1471-0048. ; 10:5, s. 345-359
  • Tidskriftsartikel (refereegranskat)abstract
    • During object manipulation tasks, the brain selects and implements action-phase controllers that use sensory predictions and afferent signals to tailor motor output to the physical properties of the objects involved. Analysis of signals in tactile afferent neurons and central processes in humans reveals how contact events are encoded and used to monitor and update task performance.
  •  
35.
  • Johansson, Roland S (författare)
  • Dynamic use of tactile afferent signals in control of dexterous manipulation.
  • 2002
  • Ingår i: Advances in Experimental Medicine and Biology. - 0065-2598 .- 2214-8019. ; 508, s. 397-410
  • Tidskriftsartikel (refereegranskat)abstract
    • During object manipulation, humans select and activate neural action programs acquired during ontogenetic development. A basic issue in understanding the control of dexterous manipulation is to learn how people use sensory information to adapt the output of these neural programs such that the fingertip actions matches the requirements imposed by the physical properties of the manipulated object, e.g., weight (mass), slipperiness, shape, and mass distribution. Although visually based identification processes contribute to predictions of required fingertip actions, the digital tactile sensors provide critical information for the control of fingertip forces. The present account deals with the tactile afferent signals from the digits during manipulation and focuses on some specific issues that the neural controller has to deal with to make use of tactile information.
  •  
36.
  • Johansson, Roland S (författare)
  • Nervceller i samarbete
  • 2008
  • Ingår i: Det friska och det sjuka nervsystemet. - Umeå : Medicinska fakulteten.
  • Bokkapitel (populärvet., debatt m.m.)
  •  
37.
  • Johansson, Roland S, et al. (författare)
  • Sensorimotor control of manipulation
  • 2009. - 8
  • Ingår i: Encyclopedia of Neuroscience. - : Elsevier. - 9780080450469 - 0080450466 ; , s. 593-604
  • Bokkapitel (populärvet., debatt m.m.)
  •  
38.
  • Johansson, Roland S, et al. (författare)
  • Sensory control of object manipulation
  • 2009
  • Ingår i: Sensorimotor control of grasping. - Cambridge : Cambridge books. - 9780511581267 ; , s. 141-160
  • Bokkapitel (populärvet., debatt m.m.)abstract
    • Series of action phases characterize natural object manipulation tasks where each phase is responsible for satisfying a task subgoal. Subgoal attainment typically corresponds to distinct mechanical contact events, either involving the making or breaking of contact between the digits and an object or between a held object and another object. Subgoals are realized by the brain selecting and sequentially implementing suitable action-phase controllers that use sensory predictions and afferents signals in specific ways to tailor the motor output in anticipation of requirements imposed by objects' physical properties. This chapter discusses the use of tactile and visual sensory information in this context. It highlights the importance of sensory predictions, especially related to the discrete and distinct sensory events associated with contact events linked to subgoal completion, and considers how sensory signals influence and interact with such predictions in the control of manipulation tasks.
  •  
39.
  • Johansson, Roland S, et al. (författare)
  • Somatosensory control of precision grip during unpredictable pulling loads. I. Changes in load force amplitude.
  • 1992
  • Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 89:1, s. 181-191
  • Tidskriftsartikel (refereegranskat)abstract
    • In manipulating 'passive' objects, for which the physical properties are stable and therefore predictable, information essential for the adaptation of the motor output to the properties of the current object is principally based on 'anticipatory parameter control' using sensorimotor memories, i.e., an internal representation of the object's properties based on previous manipulative experiences. Somatosensory afferent signals only intervene intermittently according to an 'event driven' control policy. The present study is the first in a series concerning the control of precision grip when manipulating 'active' objects that exert unpredictable forces which cannot be adequately represented in a sensorimotor memory. Consequently, the manipulation may be more reliant on a moment-to-moment sensory control. Subjects who were prevented from seeing the hand used the precision grip to restrain a manipulandum with two parallel grip surfaces attached to a force motor which produced distally directed (pulling) loads tangential to the finger tips. The trapezoidal load profiles consisted of a loading phase (4 N/s), plateau phase and an unloading phase (4 N/s) returning the load force to zero. Three force amplitudes were delivered in an unpredictable sequence; 1 N, 2 N and 4 N. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N), were superimposed on various background loads. The movement of the manipulandum, the load forces and grip forces (normal to the grip surfaces) were recorded at each finger. The grip force automatically changed with the load force during the loading and unloading phases. However, the grip responses were initiated after a brief delay. The response to the loading phase was characterized by an initial fast force increase termed the 'catch-up' response, which apparently compensated for the response delay--the grip force adequately matched the current load demands by the end of the catch-up response. In ramps with longer lasting loading phases (amplitude greater than or equal to 2 N) the catch-up response was followed by a 'tracking' response, during which the grip force increased in parallel with load force and maintained an approximately constant force ratio that prevented frictional slips. The grip force during the hold phase was linearly related to the load force, with an intercept close to the grip force used prior to the loading. Likewise, the grip force responses evoked by the fast loadings superimposed on existing loads followed the same linear relationship.(ABSTRACT TRUNCATED AT 400 WORDS)
  •  
40.
  • Johansson, Roland S, et al. (författare)
  • Somatosensory control of precision grip during unpredictable pulling loads. II. Changes in load force rate.
  • 1992
  • Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 89:1, s. 192-203
  • Tidskriftsartikel (refereegranskat)abstract
    • In the previous paper regarding the somatosensory control of the human precision grip, we concluded that the elicited automatic grip force adjustments are graded by the amplitude of the imposed loads when restraining an 'active' object subjected to unpredictable pulling forces (Johansson et al. 1992a). Using the same subjects and apparatus, the present study examines the capacity to respond to imposed load forces applied at various rates. Grip and load forces (forces normal and tangential to the grip surfaces) and the position of the object in the pulling direction (distal) were recorded. Trapezoidal load force profiles with plateau amplitudes of 2 N were delivered at the following rates of loading and unloading in an unpredictable sequence: 2 N/s, 4 N/s or 8 N/s. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N) were intermingled. The latencies between the start of the loading and the onset of the grip force response increased with decreasing load force rate. They were 80 +/- 9 ms, 108 +/- 13 ms, 138 +/- 27 ms and 174 +/- 39 ms for the 32, 8, 4 and 2 N/s rates, respectively. These data suggested that the grip response was elicited after a given minimum latency once a load amplitude threshold was exceeded. The amplitude of the initial rapid increase of grip force (i.e., the 'catch-up' response) was scaled by the rate of the load force, whereas its time course was similar for all load rates. This response was thus elicited as a unit, but its amplitude was graded by afferent information about the load rate arising very early during the loading. The scaling of the catch-up response was purposeful since it facilitated a rapid reconciliation of the ratio between the grip and load force to prevent slips. In that sense it apparently also compensated for the varying delays between the loading phase and the resultant grip force responses. However, modification of the catch-up response may occur during its course when the loading rate is altered prior to the grip force response or very early during the catch-up response itself. Hence, afferent information may be utilized continuously in updating the response although its motor expression may be confined to certain time contingencies. Moreover, this updating may take place after an extremely short latency (45-50 ms).
  •  
41.
  • Johansson, Roland S., et al. (författare)
  • Tactile sensory control of object manipulation in humans
  • 2020. - 2
  • Ingår i: The senses. - : Elsevier. - 9780128054093 - 9780128054086 ; , s. 136-152
  • Bokkapitel (refereegranskat)abstract
    • Dexterous object manipulation is a hallmark of human skill. The versatility of the human hands in manipulation tasks depends on both the anatomical structure of the hands and the neural machinery that controls them. Research during the last 20 years has led to important advances in our understanding of the sensorimotor control mechanisms that underlie dexterous object manipulation. This article focuses on the sensorimotor control of fingertip actions with special emphasis on the role of tactile sensory mechanisms. It highlights the importance of sensory predictions, especially related to mechanical contact events around which manipulation tasks are organized, and analyzes how such predictions are influenced by tactile afferent signals recorded in single neurons in awake humans.
  •  
42.
  • Kohler, Annegret, et al. (författare)
  • Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists.
  • 2015
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 47:4, s. 176-410
  • Tidskriftsartikel (refereegranskat)abstract
    • To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.
  •  
43.
  • Laschi, Cecilia, et al. (författare)
  • A Bio-inspired Neural Sensory-Motor Coordination Scheme for Robot Reaching and Preshaping
  • 2006
  • Ingår i: Proceedings of the First IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics : BioRob 2006. - Piscataway, NJ : IEEE. - 1424400406 ; , s. 531-536
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • We present a sensory-motor coordination scheme for a robot hand-arm-head system that provides the robot with the capability to reach for and to grasp an object, while pre-shaping the fingers to the required grasp configuration. A model for sensory-motor coordination derived from studies in humans inspired the development of the scheme. A special feature of this model is the prediction of the tactile image perceived after grasping. The proposed scheme is based on a neuro-fuzzy modnle that, after a learning phase, starting from visual data, calculates the position and orientation of the hand for grasping, selects the best-suited hand configuration, and predicts the tactile feedback after grasping. The implementation of the scheme on a humanoid robot ailowed experimental validation of its effectiveness in robotics and provided perspectives on applications of sensory predictions in robot motor control.
  •  
44.
  • Laschi, Cecilia, et al. (författare)
  • Bio-inspired sensory-motor coordination
  • 2008
  • Ingår i: Autonomous Robots. - : Springer. - 0929-5593 .- 1573-7527. ; 25:1-2, s. 1-2
  • Tidskriftsartikel (refereegranskat)
  •  
45.
  • Macefield, Vaughan G, et al. (författare)
  • Control of grip force during restraint of an object held between finger and thumb : responses of cutaneous afferents from the digits
  • 1996
  • Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 108:1, s. 155-171
  • Tidskriftsartikel (refereegranskat)abstract
    • Unexpected pulling and pushing loads exerted by an object held with a precision grip evoke automatic and graded increases in the grip force (normal to the grip surfaces) that prevent escape of the object; unloading elicits a decrease in grip force. Anesthesia of the digital nerves has shown that these grip reactions depend on sensory signals from the digits. In the present study we assessed the capacity of tactile afferents from the digits to trigger and scale the evoked grip responses. Using tungsten microelectrodes inserted percutaneously into the median nerve of awake human subjects, unitary recordings were made from ten FA I and 13 FA II rapidly adapting afferents, and 12 SA I and 18 SA II slowly adapting afferents. While the subject held a manipulandum between a finger and the thumb, tangential load forces were applied to the receptor-bearing digit (index, middle, or ring finger or thumb) as trapezoidal load-force profiles with a plateau amplitude of 0.5-2.0 N and rates of loading and unloading at 2-8 N/s, or as "step-loads" of 0.5 N delivered at 32 N/s. Such load trials were delivered in both the distal (pulling) and proximal (pushing) direction. FA I afferents responded consistently to the load forces, being recruited during the loading and unloading phases. During the loading ramp the ensemble discharge of the FA I afferents reflected the first time-derivative of the load force (i.e., the load-force rate). These afferents were relatively insensitive to the subject's grip force responses. However, high static finger forces appeared to suppress excitation of these afferents during the unloading phase. The FA II afferents were largely insensitive to the load trials: only with the step-loads did some afferents respond. Both classes of SA afferents were sensitive to load force and grip force, and discharge rates were graded by the rate of loading. The firing of the SA I afferents appeared to be relatively more influenced by the subject's grip-force response than the discharge of the SA II afferents, which were more influenced by the load-force stimulus. The direction in which the tangential load force was applied to the skin influenced the firing of most afferents and in particular the SA II afferents. Individual afferents within each class (except for the FA IIs) responded to the loading ramp before the onset of the subject's grip response and may thus be responsible for initiating the automatic increase in grip force. However, nearly half of the FA I afferents recruited by the load trials responded to the loading phase early enough to trigger the subject's grip-force response, whereas only ca. one-fifth of the SA Is and SA IIs did so. These observations, together with the high density of FA I receptors in the digits, might place the FA I afferents in a unique position to convey the information required to initiate and scale the reactive grip-force responses to the imposed load forces.
  •  
46.
  • Macefield, Vaughan G, et al. (författare)
  • Loads applied tangential to a fingertip during an object restraint task can trigger short-latency as well as long-latency EMG responses in hand muscles.
  • 2003
  • Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 152:2, s. 143-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrical stimulation of the digital nerves can cause short- and long-latency increases in electromyographic activity (EMG) of the hand muscles, but mechanical stimulation of primarily tactile afferents in the digits generally evokes only a long-latency increase in EMG. To examine whether such stimuli can elicit short-latency reflex responses, we recorded EMG over the first dorsal interosseous muscle when subjects (n=13) used the tip of the right index finger to restrain a horizontally oriented plate from moving when very brisk tangential forces were applied in the distal direction. The plate was subjected to ramp-and-hold pulling loads at two intensities (a 1-N load applied at 32 N/s or a 2-N load applied at 64 N/s) at times unpredictable to the subjects (mean interval 2 s; trial duration 500 ms). The contact surface of the manipulandum was covered with rayon--a slippery material. For each load, EMG was averaged for 128 consecutive trials with reference to the ramp onset. In all subjects, an automatic increase in grip force was triggered by the loads applied at 32 N/s; the mean onset latency of the EMG response was 59.8 +/- 0.9 (mean +/- SE) ms. In seven subjects (54%) this long-latency response was preceded by a weak short-latency excitation at 34.6 +/- 2.9 ms. With the loads applied at 64 N/s, the long-latency response occurred slightly earlier (58.9 +/- 1.7 ms) and, with one exception, all subjects generated a short-latency EMG response (34.9 +/- 1.3 ms). Despite the higher background grip force that subjects adopted during the stronger loads (4.9 +/- 0.3 N vs 2.5 +/- 0.2 N), the incidence of slips was higher--the manipulandum escaped from the grasp in 37 +/- 5% of trials with the 64 N/s ramps, but in only 18 +/- 4% with the 32-N/s ramps. The deformation of the fingertip caused by the tangential load, rather than incipient or overt slips, triggered the short-latency responses because such responses occurred even when the finger pad was fixed to the manipulandum with double-sided adhesive tape so that no slips occurred.
  •  
47.
  • McGarity-Shipley, Michael R., et al. (författare)
  • Fast feedback responses to categorical sensorimotor errors that do not indicate error magnitude are optimized based on short and long term memory
  • 2023
  • Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 43:49
  • Tidskriftsartikel (refereegranskat)abstract
    • Skilled motor performance depends critically on rapid corrective responses that act to preserve the goal of the movement in the face of perturbations. Although it is well established that the gain of corrective responses elicited while reaching towards objects adapts to different contexts, little is known about the adaptability of corrective responses supporting the manipulation of objects after they are grasped. Here we investigated the adaptability of the corrective response elicited when an object being lifted is heavier than expected and fails to lift off when predicted. This response involves a monotonic increase in vertical load force triggered, within ∼90 ms, by the absence of expected sensory feedback signaling lift-off, and terminated when actual lift-off occurs. Critically, because the actual weight of the object cannot be directly sensed at the moment the object fails to lift-off, any adaptation of the corrective response would have to be based on memory from previous lifts. We show that when humans, including men and women, repeatedly lift an object that, on occasional catch trials, increases from a baseline weight to a fixed heavier weight, they scale the gain of the response (i.e., the rate of force increase) to the heavier weight within 2-3 catch trials. We also show that the gain of the response scales, on the first catch trial, with the baseline weight of the object. Thus, the gain of the lifting response can be adapted by both short and long term experience. Finally, we demonstrate that this adaptation preserves the efficacy of the response across contexts.
  •  
48.
  • Nordmark, Per F., et al. (författare)
  • BOLD Responses to Tactile Stimuli in Visual and Auditory Cortex Depend on the Frequency Content of Stimulation
  • 2012
  • Ingår i: Journal of cognitive neuroscience. - Cambridge : MIT Press. - 0898-929X .- 1530-8898. ; 24:10, s. 2120-2134
  • Tidskriftsartikel (refereegranskat)abstract
    • Although some brain areas preferentially process information from a particular sensory modality, these areas can also respond to other modalities. Here we used fMRI to show that such responsiveness to tactile stimuli depends on the temporal frequency of stimulation. Participants performed a tactile threshold-tracking task where the tip of either their left or right middle finger was stimulated at 3, 20, or 100 Hz. Whole-brain analysis revealed an effect of stimulus frequency in two regions: the auditory cortex and the visual cortex. The BOLD response in the auditory cortex was stronger during stimulation at hearable frequencies (20 and 100 Hz) whereas the response in the visual cortex was suppressed at infrasonic frequencies (3 Hz). Regardless of which hand was stimulated, the frequency-dependent effects were lateralized to the left auditory cortex and the right visual cortex. Furthermore, the frequency-dependent effects in both areas were abolished when the participants performed a visual task while receiving identical tactile stimulation as in the tactile threshold-tracking task. We interpret these findings in the context of the metamodal theory of brain function, which posits that brain areas contribute to sensory processing by performing specific computations regardless of input modality.
  •  
49.
  • Nordmark, Per F., et al. (författare)
  • Disinhibition of human primary somatosensory cortex after median nerve transection and reinnervation
  • 2020
  • Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media S.A.. - 1662-5161. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite state-of-the-art surgical and postoperative treatment, median nerve transection causes lasting impaired hand function due to limitations in the nerve’s reinnervation ability. The defective innervation and thus controllability of the affected hand can shape the brain’s control of manual behaviors. Earlier studies of changes in the processing of tactile stimuli have focused mainly on stimulation of the reinnervated hand and lack sufficient control over the brain’s use of the tactile input in perceptual terms. Here we used fMRI to measure brain activity (BOLD-signal) in 11 people with median nerve injury and healthy controls (N = 11) when performing demanding tactile tasks using the tip of either the index or little finger of either hand. For the nerve-injured group, the left median nerve had been traumatically transected in the distal forearm and surgically repaired on average 8 years before the study. The hand representation of their contralesional (right) primary somatosensory cortex (S1) showed greater activity compared to controls when the left reinnervated index finger was used, but also when the left-hand little finger and the fingers of the right hand innervated by uninjured nerves were used. We argue that the overall increase in activity reflects a general disinhibition of contralesional S1 consistent with an augmented functional reorganizational plasticity being an ongoing feature of chronic recovery from nerve injury. Also, the nerve-injured showed increased activity within three prefrontal cortical areas implicated in higher-level behavioral processing (dorsal anterior cingulate cortex, left ventrolateral prefrontal and right dorsolateral prefrontal cortex), suggesting that processes supporting decision-making and response-selection were computationally more demanding due to the compromised tactile sensibility.
  •  
50.
  • Nordmark, Per F., 1981- (författare)
  • Structural and functional changes in the brain after surgically repaired median nerve injury
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Despite the best available surgical repair, traumatic median nerve injury within the forearm typically causes lifelong impairment in hand function. This stems from an inadequate reinnervation of the nerves supporting sensory functions of the thumb, index and long finger, and of nerves supplying intrinsic hand muscles. This thesis examines whether median nerve injuries can cause structural and functional changes in the brain. Understanding such changes can help the development of new treatments for improved recovery of hand function.The first study introduces a novel apparatus and paradigm for examining tactile neural processing with fMRI under well-controlled behavioral conditions. The scientific issue challenged was whether, in healthy adults, different cortical areas could be involved in processing tactile stimuli depending on their temporal frequency content. In a threshold-tracking paradigm, the participants’ task was to detect oscillatory mechanical stimulations of various frequencies delivered to the tip of either left or right middle finger. Regardless of stimulated hand, tactile detection of audible frequencies (20 and 100 Hz) engaged the left auditory cortex while detection of slow object displacements (3 Hz) engaged visual cortex. These results corroborate and advance the metamodal theory of brain function, which posits that brain areas can contribute to sensory processing by performing specific computations – those for which they are specialized – regardless of input modality.The second and third studies concern structural and functional changes in the brain of adults with one reinnervated hand after an injury transecting the median nerve in the forearm. Healthy individuals matched for sex, handedness and age served as controls. Irrespective of side of injury (left or right), voxel-based morphometry applied on T1 MR-images revealed reductions of gray matter in the left ventral and right dorsal premotor cortex, and reductions of white matter in related commissural pathways. We interpreted these as activity-dependent structural adaptations to reduced neural processing linked to restrictions in the diversity of the natural manual dexterity repertoire caused by a disturbed innervation of the hand. Conversely, increases in gray matter were observed bilaterally in a motion-processing visual cortical area. We interpreted this as a structural manifestation of increased neural processing linked to greater dependence on vision for controlling manual dexterity due to impaired tactile innervation of the affected hand.To reveal functional changes in tactile cortical processing after median nerve reinnervation, we recorded brain activity using fMRI when study participants performed perceptually demanding tactile threshold-tracking and oddball detection tasks with our novel apparatus. The hand representation of the contralesional primary somatosensory cortex (S1) showed greater activity compared to the controls when the reinnervated index finger was engaged in the tasks, but strikingly also when fingers of both hands innervated by uninjured nerves were engaged, i.e., little finger of the reinnervated hand and index and little finger of the other hand. The generally increased activity indicates a general disinhibition of contralateral S1, suggesting that increased functional reorganization is an ongoing process of chronic nerve injury. In addition, prefrontal areas implicated in processes that support decision-making and response selection showed increased activity, suggesting that such processes were more computationally demanding after nerve injury.Together, these results indicate that brain areas can undergo significant changes after peripheral nerve injury, even when followed by best available surgical repair and reinnervation conditions. These changes can include activity-dependent structural adaptations consisting of either regional decreases or increases in gray matter concentration, which likely depend on an area's functional specialization and on changes in its processing load due to behavioral constraints imposed by the injury. Moreover, the results also suggest that the affected hand's primary cortical projection area is still in a state of ongoing functional reorganization despite the fact that peripheral reinnervation of the hand should have been completed long ago, which should inspire the development of new therapeutic regimens for what today is considered a chronic impairment.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 75
Typ av publikation
tidskriftsartikel (60)
bokkapitel (6)
konferensbidrag (4)
annan publikation (2)
doktorsavhandling (2)
bok (1)
visa fler...
visa färre...
Typ av innehåll
refereegranskat (65)
övrigt vetenskapligt/konstnärligt (5)
populärvet., debatt m.m. (5)
Författare/redaktör
Laschi, Cecilia (3)
Häger, Charlotte (2)
Trulsson, Mats (2)
Johansson, Tomas (1)
Hansson, Bengt (1)
Lorentzon, Mattias, ... (1)
visa fler...
King, S. (1)
Guo, Meiyuan (1)
Lundberg, Marcus, 19 ... (1)
Veryazov, Valera (1)
Kovačević, Goran (1)
Cooper, Cyrus (1)
Díez-Pérez, Adolfo (1)
Ohlsson, Claes, 1965 (1)
Akselsson, Roland (1)
Forssberg, Hans (1)
Lind, Martin (1)
Wareham, Nicholas J. (1)
Vecchi, Fabrizio (1)
Geijer, Håkan, 1961- (1)
O'Neill, Terence W. (1)
Center, Jacqueline R (1)
Eisman, John A (1)
Nguyen, Tuan V (1)
Fagerström,, Torbjör ... (1)
Emanuelsson, Urban (1)
Souza, Domingos S. R ... (1)
Bodin, Lennart (1)
Tunlid, Anders (1)
Angeli, Celestino (1)
Knecht, Stefan (1)
Malmqvist, Per-Åke (1)
Axelsson, J (1)
Wallander, Håkan (1)
Johansson, Curt R. (1)
Odenrick, Per (1)
Dalholm Hornyánszky, ... (1)
Kihlberg, S (1)
Mathiassen, S E (1)
Wikström, Tomas (1)
Winkel, J (1)
Eklund, J (1)
Bergman, B (1)
Grigoriadis, A (1)
Alavi, Ali (1)
McGuigan, F E A (1)
McGuigan, Fiona E.A. (1)
Mellström, Dan, 1945 (1)
Johansson, Leif (1)
Nordström, Peter (1)
visa färre...
Lärosäte
Umeå universitet (69)
Lunds universitet (6)
Karolinska Institutet (4)
Uppsala universitet (2)
Mittuniversitetet (2)
Göteborgs universitet (1)
visa fler...
Kungliga Tekniska Högskolan (1)
Stockholms universitet (1)
Örebro universitet (1)
Sveriges Lantbruksuniversitet (1)
visa färre...
Språk
Engelska (73)
Svenska (2)
Forskningsämne (UKÄ/SCB)
Medicin och hälsovetenskap (47)
Naturvetenskap (5)
Teknik (2)
Samhällsvetenskap (2)
Lantbruksvetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy