| 1. |
- Jönsson, Emma H., et al.
(författare)
-
The relation between human hair follicle density and touch perception
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Unmyelinated low threshold C-tactile fibers moderate pleasant aspects of touch. These fibers respond optimally to stroking stimulation of the skin with slow velocities (1-10 cm/s). Low threshold mechanoreceptors are arranged around hair follicles in rodent skin. If valid also in humans, hair follicle density (HFD) may relate to the perceived pleasantness of stroking tactile stimulation. We conducted two studies that examined the relation between HFD and affective touch perception in humans. In total, 138 healthy volunteers were stroked on the forearm and rated the pleasantness and intensity. Stimulation was performed by a robotic tactile stimulator delivering C-tactile optimal (1, 3, 10 cm/s) and non-optimal (0.1, 0.3, 30 cm/s) stroking velocities. Additionally, a measure of discriminative touch was applied in study 2. HFD of the same forearm was determined using the Cyanoacrylate Skin Stripping Method (CSSM), which we validated in a pretest. Women had higher HFD than men, which was explained by body size and weight. Furthermore, women rated affective touch stimuli as more pleasant and had higher tactile acuity. Depilation did not affect touch perception. A weak relationship was found between the C-tactile specific aspects of affective touch perception and HFD, and the hypothesis of HFD relating to pleasant aspects of stroking only received weak support.
|
|
| 2. |
- Ackerley, Rochelle, 1980, et al.
(författare)
-
Case Studies in Neuroscience: Sensations elicited and discrimination ability from nerve cuff stimulation in an amputee over time
- 2018
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 120:1, s. 291-295
-
Tidskriftsartikel (refereegranskat)abstract
- The present case study details sensations elicited by electrical stimulation of peripheral nerve axons using an implanted nerve cuff electrode, in a participant with a transhumeral amputation. The participant uses an osseointegrated electromechanical interface, which enables skeletal attachment of the prosthesis and long-term, stable, bidirectional communication between the implanted electrodes and prosthetic arm. We focused on evoking somatosensory percepts, where we tracked and quantified the evolution of perceived sensations in the missing hand. which were evoked from electrical stimulation of the nerve, for over 2 yr. These sensations included small, pointlike areas of either vibration or pushing, to larger sensations over wider areas, indicating the recruitment of a few and many afferents, respectively. Furthermore, we used a two-alternative forced choice paradigm to measure the level of discrimination between trains of brief electrical stimuli, to gauge what the participant could reliably distinguish between. At best, the participant was able to distinguish a 05-Hz difference and on average acquired a 3.8-Hz just-noticeable difference at a more stringent psychophysical level. The current work shows the feasibility for long-term sensory feedback in prostheses, via electrical axonal stimulation, where small and relatively stable percepts were felt that may be used to deliver graded sensory feedback. This opens up opportunities for signaling feedback during movements (e.g., for precision grip), but also for conveying more complex cutaneous sensations. such as texture. NEW & NOTEWORTHY We demonstrate the long-term stability and generation of sensations from electrical peripheral nerve stimulation in an amputee. through an osseointegrated implant. We find that perceived tactilelike sensations could be generated for over 2 yr. in the missing hand. This is useful for prosthetic development and the implementation of feedback in artificial body parts.
|
|
| 3. |
- Sanchez, Justin C, et al.
(författare)
-
Interpreting spatial and temporal neural activity through a recurrent neural network brain-machine interface.
- 2005
-
Ingår i: IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society. - 1534-4320. ; 13:2, s. 213-9
-
Tidskriftsartikel (refereegranskat)abstract
- We propose the use of optimized brain-machine interface (BMI) models for interpreting the spatial and temporal neural activity generated in motor tasks. In this study, a nonlinear dynamical neural network is trained to predict the hand position of primates from neural recordings in a reaching task paradigm. We first develop a method to reveal the role attributed by the model to the sampled motor, premotor, and parietal cortices in generating hand movements. Next, using the trained model weights, we derive a temporal sensitivity measure to asses how the model utilized the sampled cortices and neurons in real-time during BMI testing.
|
|
| 4. |
- Wessberg, Johan, 1962, et al.
(författare)
-
Optimizing a linear algorithm for real-time robotic control using chronic cortical ensemble recordings in monkeys.
- 2004
-
Ingår i: Journal of cognitive neuroscience. - : MIT Press - Journals. - 0898-929X .- 1530-8898. ; 16:6, s. 1022-35
-
Tidskriftsartikel (refereegranskat)abstract
- Previous work in our laboratory has demonstrated that a simple linear model can be used to translate cortical neuronal activity into real-time motor control commands that allow a robot arm to mimic the intended hand movements of trained primates. Here, we describe the results of a comprehensive analysis of the contribution of single cortical neurons to this linear model. Key to the operation of this model was the observation that a large percentage of cortical neurons located in both frontal and parietal cortical areas are tuned for hand position. In most neurons, hand position tuning was time-dependent, varying continuously during a 1-sec period before hand movement onset. The relevance of this physiological finding was demonstrated by showing that maximum contribution of individual neurons to the linear model was only achieved when optimal parameters for the impulse response functions describing time-varying neuronal position tuning were selected. Optimal parameters included impulse response functions with 1.0- to 1.4-sec time length and 50- to 100-msec bins. Although reliable generalization and long-term predictions (60-90 min) could be achieved after 10-min training sessions, we noticed that the model performance degraded over long periods. Part of this degradation was accounted by the observation that neuronal position tuning varied significantly throughout the duration (60-90 min) of a recording session. Altogether, these results indicate that the experimental paradigm described here may be useful not only to investigate aspects of neural population coding, but it may also provide a test bed for the development of clinically useful cortical prosthetic devices aimed at restoring motor functions in severely paralyzed patients.
|
|
| 5. |
- McGlone, Francis, et al.
(författare)
-
Discriminative and Affective Touch: Sensing and Feeling.
- 2014
-
Ingår i: Neuron. - : Elsevier BV. - 1097-4199 .- 0896-6273. ; 82:4, s. 737-755
-
Forskningsöversikt (refereegranskat)abstract
- The multimodal properties of the human somatosensory system continue to be unravelled. There is mounting evidence that one of these submodalities-touch-has another dimension, providing not only its well-recognized discriminative input to the brain, but also an affective input. It has long been recognized that touch plays an important role in many forms of social communication and a number of theories have been proposed to explain observations and beliefs about the "power of touch." Here, we propose that a class of low-threshold mechanosensitive C fibers that innervate the hairy skin represent the neurobiological substrate for the affective and rewarding properties of touch.
|
|
| 6. |
- Åberg, Malin C B, et al.
(författare)
-
Evolutionary optimization of classifiers and features for single trial EEG Discrimination.
- 2007
-
Ingår i: Biomedical Engineering Online. - : BioMed Central (BMC). - 1475-925X. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: State-of-the-art signal processing methods are known to detect information in single trial event-related EEG data, a crucial aspect in development of real-time applications such as brain computer interfaces. This paper investigates one such novel approach, evaluating how individual classifier and feature subset tailoring affects classification of single trial EEG finger movements. The discrete wavelet transform was used to extract signal features that were classified using linear regression and non-linear neural network models, which were trained and architecturally optimized with evolutionary algorithms. The input feature subsets were also allowed to evolve, thus performing feature selection in a wrapper fashion. Filter approaches were implemented as well by limiting the degree of optimization. RESULTS: Using only 10 features and 100 patterns, the non-linear wrapper approach achieved the highest validation classification accuracy (subject mean 75%), closely followed by the linear wrapper method (73.5%). The optimal features differed much between subjects, yet some physiologically plausible patterns were observed. CONCLUSIONS: High degrees of classifier parameter, structure and feature subset tailoring on individual levels substantially increase single-trial EEG classification rates, an important consideration in areas where highly accurate detection rates are essential. Also, the presented method provides insight into the spatial characteristics of finger movement EEG patterns.
|
|
| 7. |
- Olausson, Håkan, 1965, et al.
(författare)
-
Functional role of unmyelinated tactile afferents in human hairy skin: sympathetic response and perceptual localization.
- 2008
-
Ingår i: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. - : Springer Science and Business Media LLC. - 1432-1106. ; 184:1, s. 135-40
-
Tidskriftsartikel (refereegranskat)abstract
- In addition to A-beta fibres the human hairy skin has unmyelinated (C) fibres responsive to light touch. Previous functional magnetic resonance imaging (fMRI) studies in a subject with a neuronopathy who specifically lacks A-beta afferents indicated that tactile C afferents (CT) activate insular cortex, whereas no response was seen in somatosensory areas 1 and 2. Psychophysical tests suggested that CT afferents give rise to an inconsistent perception of weak and pleasant touch. By examining two neuronopathy subjects as well as control subjects we have now demonstrated that CT stimulation can elicit a sympathetic skin response. Further, the neuronopathy subjects' ability to localize stimuli which activate CT afferents was very poor but above chance level. The findings support the interpretation that the CT system is well suited to underpin affective rather than discriminative functions of tactile sensations.
|
|
| 8. |
- Glover, P. M., et al.
(författare)
-
An intra-neural microstimulation system for ultra-high field magnetic resonance imaging and magnetoencephalography
- 2017
-
Ingår i: Journal of Neuroscience Methods. - : Elsevier BV. - 0165-0270. ; 290, s. 69-78
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Intra-neural microstimulation (INMS) is a technique that allows the precise delivery of low-current electrical pulses into human peripheral nerves. Single unit INMS can be used to stimulate individual afferent nerve fibres during microneurography. Combining this with neuroimaging allows the unique monitoring of central nervous system activation in response to unitary, controlled tactile input, with functional magnetic resonance imaging (fMRI) providing exquisite spatial localisation of brain activity and magnetoencephalography (MEG) high temporal resolution. New method: INMS systems suitable for use within electrophysiology laboratories have been available for many years. We describe an INMS system specifically designed to provide compatibility with both ultra-high field (7 T) fMRI and MEG. Numerous technical and safety issues are addressed. The system is fully analogue, allowing for arbitrary frequency and amplitude INMS stimulation. Results: Unitary recordings obtained within both the MRI and MEG screened -room environments are comparable with those obtained in 'clean' electrophysiology recording environments. Single unit INMS (current <7 mu A, 200 mu s pulses) of individual mechanoreceptive afferents produces appropriate and robust responses during fMRI and MEG. Comparison with existing method(s): This custom-built MRI- and MEG-compatible stimulator overcomes issues with existing INMS approaches; it allows well-controlled switching between recording and stimulus mode, prevents electrical shocks because of long cable lengths, permits unlimited patterns of stimulation, and provides a system with improved work-flow and participant comfort. Conclusions: We demonstrate that the requirements for an INMS-integrated system, which can be used with both fMRI and MEG imaging systems, have been fully met. (C) 2017 The Author(s). Published by Elsevier B.V.
|
|
| 9. |
- Dione, Mariama, 1987, et al.
(författare)
-
Human 8-to 10-Hz pulsatile motor output during active exploration of textured surfaces reflects the textures' frictional properties
- 2019
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 122:3, s. 922-932
-
Tidskriftsartikel (refereegranskat)abstract
- Active sensing in biological system consists of emitting/receiving a periodic signal to explore the environment. The signal can be emitted toward distant objects. as in echolocation, or in direct contact with the object. for example, whisking in rodents. We explored the hypothesis that a similar mechanism exists in humans. Humans generate periodic signals at similar to 10 Hz during voluntary finger movements, which reflects a pulsatile motor command in the central nervous system. In the present study, we tested whether the similar to 10-Hz signal persists during the active exploration of textures and whether the textures' features can modulate the signal. Our results confirm our assumptions. The similar to 10-Ilz signal persisted during active touch, and its amplitude increased with textures of higher friction. These findings support the idea that the similar to 10-Hz periodic signal generated during voluntary finger movements is part of an active sensing mechanism acting in a pulse-amplitude modulation fashion to convey relevant tactile information to the brain. NEW & NOTEWORTHY For the first time, we show that pulsatile motor output during voluntary movement of a finger persists during active exploration of a surface. We propose that this is part of an active sensing system in humans, with generation of an similar to 10-Hz signal during active touch that reinforces extraction of information about features of the touched surface.
|
|
| 10. |
- Watkins, R. H., et al.
(författare)
-
Slowly-adapting type II afferents contribute to conscious touch sensation in humans: Evidence from single unit intraneural microstimulation
- 2022
-
Ingår i: Journal of Physiology-London. - : Wiley. - 0022-3751 .- 1469-7793. ; 600:12, s. 2939-2952
-
Tidskriftsartikel (refereegranskat)abstract
- Slowly-adapting type II (SA-II, Ruffini) mechanoreceptive afferents respond well to pressure and stretch, and are regularly encountered in human microneurography studies. Despite an understanding of SA-II response properties, their role in touch perception remains unclear. Specific roles of different myelinated A beta mechanoreceptive afferents in tactile perception have been revealed using single unit intraneural microstimulation (INMS), via microneurography, recording from and then electrically stimulating individual afferents. This method directly links single afferent artificial activation to perception, where INMS produces specific 'quantal' touch percepts associated with different mechanoreceptive afferent types. However, SA-II afferent stimulation has been ambiguous, producing inconsistent, vague sensations, or no clear percept. We physiologically characterized hundreds of individual A beta mechanoreceptive afferents in the glabrous hand skin and examined the subsequent percepts evoked by trains of low amplitude INMS current pulses (<10 mu A). We present 18 SA-II afferents where INMS resulted in a clear, electrically evoked sensation of large (similar to 36 mm(2)) diffuse pressure, which was projected precisely to their physiologically-defined receptive field in the skin. This sensation was felt as natural, distinctive from other afferents, and showed no indications of multi-afferent stimulation. Stimulus frequency modulated sensation intensity and even brief stimuli (4 pulses, 60 ms) were perceived. These results suggest that SA-II afferents contribute to perceived tactile sensations, can signal this rapidly and precisely, and are relevant and important for computational models of touch sensation and artificial prosthetic feedback. Key points Slowly adapting type II mechanoreceptors (SA-IIs) are primary sensory neurons in humans that respond to pressure and stretch applied to the skin. To date, no specific conscious correlate of touch has been linked to SA-II activation. Using microneurography and intraneural microstimulation to stimulate single sensory neurons in human subjects, we find a specific sensation linked to the activation of single SA-II afferents. This sensation of touch was reported as gentle pressure and subjects could detect this with a high degree of accuracy. Methods of artificial tactile sensory feedback and computational models of touch should include SA-IIs as meaningful contributors to the conscious sensation of touch.
|
|
