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- Ackerley, Rochelle, 1980, et al.
(author)
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Case Studies in Neuroscience: Sensations elicited and discrimination ability from nerve cuff stimulation in an amputee over time
- 2018
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In: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 120:1, s. 291-295
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Journal article (peer-reviewed)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.
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| 2. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Differential effects of radiant and mechanically applied thermal stimuli on human C-tactile afferent firing patterns.
- 2018
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In: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 120:4, s. 1885-1892
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Journal article (peer-reviewed)abstract
- C-tactile (CT) afferents respond to gentle tactile stimulation, but only a handful of studies in humans and animals have investigated whether their firing is modified by temperature. We describe the effects of radiant thermal stimuli, and of stationary and very slowly moving mechanothermal stimuli, on CT afferent responses. We find that CT afferents are primarily mechanoreceptors, as they fired little during radiant thermal stimuli, but they exhibited different patterns of firing during combined mechano-cool stimulation compared with warming. CTs fired optimally to gentle, very slowly moving, or stationary mechanothermal stimuli delivered at neutral temperature (~32°C, normal skin temperature), but they responded with fewer spikes (median 67% decrease) and at significantly lower rates (47% decrease) during warm (~42°C) tactile stimuli. During cool tactile stimuli (~18°C), their mean instantaneous firing frequency significantly decreased by 35%, but they often fired a barrage of afterdischarge spikes at a low frequency (~5 Hz) that outlasted the mechanical stimulus. These effects were observed under a variety of stimulus conditions, including during stationary and slowly moving touch (0.1 cm/s), and we complemented these tactile approaches using a combined electrical-thermal stimulation experiment where we found a suppression of spiking during warming. Overall, CT afferents are exquisitely sensitive to tactile events, and we show that their firing is modulated with touch temperatures above and below neutral skin temperature. Warm touch consistently decreased their propensity to fire, whereas cool touch produced lower firing rates but afterdischarge spiking. NEW & NOTEWORTHY C-tactile (CT) afferents are thought to underpin pleasant touch, and previous work has shown that they respond optimally to a slow caress delivered at typical (neutral) skin temperature. Here, we show that, although CTs are primarily mechanoreceptive afferents, they are modified by temperature: warm touch decreases their firing, whereas cool touch produces lower firing rates but long-lasting spiking, frequently seen as afterdischarges. This has implications for the encoding of affective sensory events in human skin.
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| 4. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Human C-tactile afferents are tuned to the temperature of a skin-stroking caress
- 2014
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In: Journal of Neuroscience. - 0270-6474. ; 34:8, s. 2879-2883
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Journal article (peer-reviewed)abstract
- Human C-tactile (CT) afferents respond vigorously to gentle skin stroking and have gained attention for their importance in social touch. Pharmacogenetic activation of the mouse CT equivalent has positively reinforcing, anxiolytic effects, suggesting a role in grooming and affiliative behavior. We recorded from single CT axons in human participants, using the technique of microneurography, and stimulated a unit's receptive field using a novel, computer-controlled moving probe, which stroked the skin of the forearm over five velocities (0.3, 1, 3, 10, and 30 cm s-1) at three temperatures (cool, 18°C; neutral, 32°C; warm, 42°C). We show that CTs are unique among mechanoreceptive afferents: they discharged preferentially to slowly moving stimuli at a neutral (typical skin) temperature, rather than at the cooler or warmer stimulus temperatures. In contrast, myelinated hair mechanoreceptive afferents proportionally increased their firing frequency with stroking velocity and showed no temperature modulation. Furthermore, the CT firing frequency correlated with hedonic ratings to the same mechano-thermal stimulus only at the neutral stimulus temperature, where the stimuli were felt as pleasant at higher firing rates. We conclude that CT afferents are tuned to respond to tactile stimuli with the specific characteristics of a gentle caress delivered at typical skin temperature. This provides a peripheral mechanism for signaling pleasant skin-to-skin contact in humans, which promotes interpersonal touch and affiliative behavior. © 2014 the authors.
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| 6. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Quantifying the sensory and emotional perception of touch: Differences between glabrous and hairy skin
- 2014
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In: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 8:FEB
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Journal article (peer-reviewed)abstract
- The perception of touch is complex and there has been a lack of ways to describe the full tactile experience quantitatively. Guest et al. (2011) developed a Touch Perception Task (TPT) in order to capture such experiences, and here we used the TPT to examine differences in sensory and emotional aspects of touch at different skin sites. We compared touch on three skin sites: the hairy arm and cheek, and the glabrous palm. The hairy skin contains C-tactile (CT) afferents, which play a role in affective touch, whereas glabrous skin does not contain CT afferents and is involved in more discriminative touch. In healthy volunteers, three different materials (soft brush, sandpaper, fur) were stroked across these skin sites during self-touch or experimenter-applied touch. After each stimulus, participants rated the tactile experience using descriptors in the TPT. Sensory and emotional descriptors were analyzed using factor analyses. Five sensory factors were found: Texture, Pile, Moisture, Heat/Sharp and Cold/Slip, and three emotional factors: Positive Affect, Arousal, and Negative Affect. Significant differences were found in the use of descriptors in touch to hairy vs. glabrous skin: this was most evident in touch on forearm skin, which produced higher emotional content. The touch from another was also judged as more emotionally positive then self-touch, and participants readily discriminated between the materials on all factors. The TPT successfully probed sensory and emotional percepts of the touch experience, which aided in identifying skin where emotional touch was more pertinent. It also highlights the potentially important role for CTs in the affective processing of inter-personal touch, in combination with higher-order influences, such as through cultural belonging and previous experiences. © 2014 Ackerley, Saar, McGlone and Backlund Wasling.
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| 7. |
- Ackerley, Rochelle, 1980, et al.
(author)
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The touch landscape
- 2016
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In: Affective Touch and the Neurophysiology of CT Afferents. Olausson H., Wessberg J., Morrison I., McGlone F. (eds.). - New York, NY : Springer. - 9781493964185 ; , s. 85-109
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Book chapter (other academic/artistic)abstract
- Somatic sensation comprises four main modalities relaying tactile, thermal, painful, or pruritic (itch) information to the central nervous system. These input channels can be further classified as sub-serving sensory functions, such as spatial and temporal discrimination, and the provision of essential information for controlling and guiding exploratory manual behaviours, or affective functions that include the provision of the subjective experience of affective or emotional pleasurable touch. Signalling in fast-conducting myelinated peripheral nerve fibres (Aβ afferents) is important for the discriminative properties of tactile sensations, whereas signalling in unmyelinated peripheral nerve fibres, C-tactile (CT) afferents seems to be important for the rewarding, emotional properties of touch. CT afferents have specific biophysical, electrophysiological, neurobiological and anatomical properties to drive the temporally delayed affective somatic system. This chapter explores step by step the differences between the discriminative and affective touch systems, from the first stage of encoding touch in the skin to the neural pathways in the brain. The below quote from Bentley (Am J Psychol 11:405-425, 1900) reiterates the complexity of the skin and the wonder in the phenomenon of somatosensation: ‘The skin is burdened with offices. One of the surprises of physiology is the revelation of the multitude of functions performed by this apparently simple organ. As a rind it is not only the container, but the warder-off, and also the go-between for the organism and its world; tegument, buckler, interagent. It is small wonder that its work is represented in mental process; that many of our most worn and useful perceptions are made up of cutaneous sensations.'. © 2016 Springer Science+Business Media New York.
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| 8. |
- Ackerley, Rochelle, 1980, et al.
(author)
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Touch perceptions across skin sites: Differences between sensitivity, direction discrimination and pleasantness
- 2014
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In: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 8:54
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Journal article (peer-reviewed)abstract
- Human skin is innervated with different tactile afferents, which are found at varying densities over the body. We investigate how the relationships between tactile pleasantness, sensitivity and discrimination differ across the skin. Tactile pleasantness was assessed by stroking a soft brush over the skin, using five velocities (0.3, 1, 3, 10, 30 cm s-1), known to differentiate hedonic touch, and pleasantness ratings were gained. The ratings velocity-profile is known to correlate with firing in unmyelinated C-tactile (CT) afferents. Tactile sensitivity thresholds were determined using monofilament force detection and the tactile discrimination level was obtained in the direction discrimination of a moving probe; both tasks readily activate myelinated touch receptors. Perceptions were measured over five skin sites: forehead, arm, palm, thigh and shin. The assessment of tactile pleasantness over the skin resulted in a preference for the middle velocities (1-10 cm s-1), where higher ratings were gained compared to the slowest and fastest velocities. This preference in tactile pleasantness was found across all the skin sites, apart from at the palm, where no decrease in pleasantness for the faster stroking velocities was seen. We find that tactile sensitivity and discrimination vary across the skin, where the forehead and palm show increased acuity. Tactile sensitivity and discrimination levels also correlated significantly, although the tactile acuity did not relate to the perceived pleasantness of touch. Tactile pleasantness varied in a subtle way across skin sites, where the middle velocities were always rated as the most pleasant, but the ratings at hairy skin sites were more receptive to changes in stroking velocity. We postulate that although the mechanoreceptive afferent physiology may be different over the skin, the perception of pleasant touch can be interpreted using all of the available incoming somatosensory information in combination with central processing. © 2014 Ackerley, Carlsson, Wester, Olausson and Backlund Wasling.
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| 9. |
- Backlund, Helena, 1972
(author)
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Functional aspects of tactile directional sensibility
- 2004
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Doctoral thesis (other academic/artistic)abstract
- Tactile directional sensibility, i.e. the ability to tell the movement direction of a moving tactile stimulus, depends on the parallel processing of spatiotemporal information and information about changes in the pattern of skin tension. Over the last decade, the peripheral mechanisms underlying directional sensibility have been extensively studied. However, knowledge about information processing on the supraspinal level is limited. Directional sensibility provides a sensitive test for disturbances in the peripheral and central nervous systems. The high aptitude of directional sensibility also raises the question of the functional role of this perceptual capacity. In the first part of the study, subjects determined the direction of skin pulls on the lower leg during functional magnetic resonance imaging. We found bilateral activation in second somatosensory (S2) and insular cortices (IC) but no activation in first somatosensory cortex (S1). In addition, four hemispherectomized patients and six healthy control subjects were examined for touch detection thresholds and directional sensibility. For the paretic side, the patients could not tell the direction of movement of a tactile stimulus whereas touch detection was often in the normal range. On the nonparetic side, patients always performed within the normal range.In the second part the hypothesis was tested that directional sensibility of the hairy skin is important for motor control. It was shown that non-supportive tactile contact between the forearm skin and spatially fixed tactile objects could reduce postural sway. It was further found that spatiotemporal information (air-stream stimulus) improved postural control when applied to the fingertip, but to much lesser extent when applied to the forearm. Skin stretch information (glued rod stimulus) reduced sway when applied to both glabrous and hairy skin. Conclusion: The contralateral hemisphere, especially S2 and IC, is important for processing of tactile directional information. Skin stretch information from both glabrous and hairy skin can attenuate postural sway whereas spatiotemporal information is most effective when emanating in the glabrous skin. The present findings will improve the clinical usefulness of the directional sensibility test. The work also demonstrates that the human hairy skin is important for postural control which may lead to new rehabilitation strategies for patients at risk of falling.
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