ORCID Profile
0000-0003-4916-1254
Current Organisations
Neuroscience Research Australia
,
MARCS Institute for Brain, Behaviour and Development
,
UNSW Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Sensory Systems | Sensory Processes, Perception and Performance | Neurosciences | Peripheral Nervous System | Sensory systems | Psychology | Sensory processes perception and performance | Neurosciences | Motor control
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences | Expanding Knowledge in Engineering | Skin and Related Disorders |
Related Links
Publications
Memory at your fingertips: how viscoelasticity affects tactile neuron signaling
Publisher: eLife Sciences Publications, Ltd
Date: 05-09-2023
DOI: 10.7554/ELIFE.89616
Decoding tactile afferent activity to obtain an estimate of instantaneous force and torque applied to the fingerpad
Publisher: American Physiological Society
Date: 07-2015
Abstract: Dexterous manipulation is not possible without sensory information about object properties and manipulative forces. Fundamental neuroscience has been unable to demonstrate how information about multiple stimulus parameters may be continuously extracted, concurrently, from a population of tactile afferents. This is the first study to demonstrate this, using spike trains recorded from tactile afferents innervating the monkey fingerpad. A multiple-regression model, requiring no a priori knowledge of stimulus-onset times or stimulus combination, was developed to obtain continuous estimates of instantaneous force and torque. The stimuli consisted of a normal-force r (to a plateau of 1.8, 2.2, or 2.5 N), on top of which −3.5, −2.0, 0, +2.0, or +3.5 mNm torque was applied about the normal to the skin surface. The model inputs were sliding windows of binned spike counts recorded from each afferent. Models were trained and tested by 15-fold cross-validation to estimate instantaneous normal force and torque over the entire stimulation period. With the use of the spike trains from 58 slow-adapting type I and 25 fast-adapting type I afferents, the instantaneous normal force and torque could be estimated with small error. This study demonstrated that instantaneous force and torque parameters could be reliably extracted from a small number of tactile afferent responses in a real-time fashion with stimulus combinations that the model had not been exposed to during training. Analysis of the model weights may reveal how interactions between stimulus parameters could be disentangled for complex population responses and could be used to test neurophysiologically relevant hypotheses about encoding mechanisms.
Melatonin agonist tasimelteon (VEC-162) for transient insomnia after sleep-time shift: two randomised controlled multicentre trials
Publisher: Elsevier BV
Date: 02-2009
The Bayesian decoding of force stimuli from slowly adapting type I fibers in humans
Publisher: Public Library of Science (PLoS)
Date: 14-04-2016
Temporal patterns in electrical nerve stimulation: Burst gap code shapes tactile frequency perception
Publisher: Public Library of Science (PLoS)
Date: 13-08-2020
Can Video Self-Modeling Improve Affected Limb Reach and Grasp Ability in Stroke Patients?
Publisher: Informa UK Limited
Date: 19-05-2017
DOI: 10.1080/00222895.2017.1306480
Abstract: The authors examined whether feedforward video self-modeling (FF VSM) would improve control over the affected limb, movement self-confidence, movement self-consciousness, and well-being in 18 stroke survivors. Participants completed a cup transport task and 2 questionnaires related to psychological processes pre- and postintervention. Pretest video footage of the unaffected limb performing the task was edited to create a best-of or mirror-reversed training DVD, creating the illusion that patients were performing proficiently with the affected limb. The training yielded significant improvements for the forward movement of the affected limb compared to the unaffected limb. Significant improvements were also seen in movement self-confidence, movement self-consciousness, and well-being. FF VSM appears to be a viable way to improve motor ability in populations with movement disorders.
Modulation of human muscle spindle discharge by arterial pulsations - functional effects and consequences
Publisher: Public Library of Science (PLoS)
Date: 17-04-2012
Submillimeter Lateral Displacement Enables Friction Sensing and Awareness of Surface Slipperiness
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2022
Tactile sensory channels over-ruled by frequency decoding system that utilizes spike pattern regardless of receptor type
Publisher: Cold Spring Harbor Laboratory
Date: 09-03-2019
DOI: 10.1101/570929
Abstract: The established view is that vibrotactile stimuli evoke two qualitatively distinctive cutaneous sensations, flutter (frequencies 60 Hz) and vibratory hum (frequencies 60 Hz), subserved by two distinct receptor types (Meissner’s and Pacinian corpuscle, respectively) which may engage different neural processing pathways or channels and fulfill quite different biological roles. In psychological and physiological literature those two systems have been labelled as Pacinian and non-Pacinian channels. However, we present evidence that low-frequency spike trains in Pacinian afferents can readily induce a vibratory percept with the same low frequency attributes as sinusoidal stimuli of the same frequency thus demonstrating a universal frequency decoding system. We achieved this using brief low- litude pulsatile mechanical stimuli to selectively activate Pacinian afferents. This indicates that spiking pattern, regardless of receptor type, determines vibrotactile frequency perception. This mechanism may underlie the constancy of vibrotactile frequency perception across different skin regions innervated by distinct afferent types.
Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation
Publisher: American Physiological Society
Date: 10-1998
DOI: 10.1152/JN.1998.80.4.1989
Abstract: Birznieks, Ingvars, Magnus K. O. Burstedt, Benoni B. Edin, and Roland S. Johansson. Mechanisms for force adjustments to unpredictable frictional changes at in idual digits during two-fingered manipulation. J. Neurophysiol. 80: 1989–2002, 1998. Previous studies on adaptation of fingertip forces to local friction at in idual 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 r 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.
Memory at your fingertips: how viscoelasticity affects tactile neuron signaling
Publisher: Cold Spring Harbor Laboratory
Date: 17-05-2023
DOI: 10.1101/2023.05.15.540820
Abstract: Human skin and its underlying tissues constitute a viscoelastic medium, implying that any deformation depends not only on the currently applied force, but also the recent loading history. The extent to which this physical memory influences the signaling of first-order tactile neurons during natural hand use is not well understood. Here, we examined the effect of past loading on the responses of fast-adapting (FA-1) and slowly-adapting (SA-1 and SA-2) first-order tactile neurons innervating the human fingertip to loadings applied in different directions representative of object manipulation tasks. We found that variation in the preceding loading affected neurons’ overall signaling of force direction. Some neurons kept signaling the current direction, while others signaled both the current and preceding direction, or even primarily the preceding direction. In addition, ongoing impulse activity in SA-2 neurons between loadings signaled information related to the fingertip’s viscoelastic deformation state between loadings. We conclude that tactile neurons at the population level signal continuous information about the fingertip’s viscoelastic deformation state, which is shaped by both its recent history and current loading. Such information might be sufficient for the brain to correctly interpret current force loading and help in computing accurate motor commands for interactions with objects in manipulation and haptic tasks.
Author response: Tactile sensory channels over-ruled by frequency decoding system that utilizes spike pattern regardless of receptor type
Publisher: eLife Sciences Publications, Ltd
Date: 15-07-2019
Adaptation to Motion Presented with a Tactile Array
Publisher: Springer Berlin Heidelberg
Date: 2014
Burst gap code predictions for tactile frequency are valid across the range of perceived frequencies attributed to two distinct tactile channels
Publisher: American Physiological Society
Date: 02-2021
Abstract: We present evidence for a generalized frequency processing strategy on tactile afferent inputs that is shared across a broad range of frequencies extending beyond the flutter range, supporting the notion that spike timing has an important role in shaping tactile perception.
Differential sensitivity to surface compliance by tactile afferents in the human finger pad
Publisher: American Physiological Society
Date: 15-03-2014
Abstract: We undertook a neurophysiological investigation of the responses of low-threshold mechanoreceptors in the human finger pad to surfaces of differing softness. Unitary recordings were made from 26 slowly adapting type I (SAI), 17 fast-adapting type I (FAI), and 9 slowly adapting type II (SAII) afferents via tungsten microelectrodes inserted into the median nerve at the wrist. A servo-controlled stimulator applied r -and-hold forces (1, 2, 4 N) at a constant loading and unloading rate (2 N/s) via a flat silicone disc over the center of the finger pad. Nine discs were used, which linearly increased in stiffness across the range. Population responses of the SAI afferents showed the greatest sensitivity to compliance, with a steep monotonic increase in mean firing rate with increasing stiffness (decreasing compliance) of the surface during the loading and plateau (but not unloading) phases. FAI afferents also showed a linear increase in firing during the loading but not unloading phase, although the slope was significantly lower than that of the SAI afferents at all litudes. Conversely, SAII afferents were influenced by object compliance only in certain conditions. Given their high density in the finger pads and their linear relationship between firing rate and object compliance during the loading and plateau phases, SAI afferents (together with FAI afferents during the loading phase) are ideally suited to contributing information on surface compliance to the overall estimation of softness, but the SAII afferents appear to play only a minor role.
Haptics in Neuroscience
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2016
Effects of deep and superficial experimentally induced acute pain on skin sympathetic nerve activity in human subjects
Publisher: Springer Science and Business Media LLC
Date: 14-04-2009
DOI: 10.1007/S00221-009-1790-9
Abstract: There is evidence in experimental animals that deep and superficial pain exert differential effects on cutaneous sympathetic activity. Skin sympathetic nerve activity (SSNA) was recorded from the common peroneal nerve of awake human subjects and injections of 0.5 ml hypertonic saline was made into the tibialis anterior muscle (causing a deep, dull ache) or 0.2 ml into the overlying skin (causing a sharp burning pain) at unexpected times. Both deep and superficial pain caused increases in SSNA immediately on injection and preceding the onset of pain for both muscle and skin pain (10.1 +/- 2.4 vs. 15.3 +/- 5.3 s muscle versus skin, respectively). SSNA increases were short lasting (104.2 +/- 13.4 vs. 81.8 +/- 11.7 s muscle versus skin pain) and did not follow muscle and skin pain profiles. Sweat release occurred following both intramuscular and subcutaneous injections of hypertonic saline. While muscle or skin pain invariably caused changes in skin blood flow as well as increases in sweat release, skin blood flow increased in females and decreased in males. We conclude that both acute muscle and skin pain cause an increase in SSNA, sweat release and gender-dependent changes in skin blood flow.
Tapping Into the Language of Touch: Using Non-invasive Stimulation to Specify Tactile Afferent Firing Patterns
Publisher: Frontiers Media SA
Date: 19-05-2020
Recent progress in artificial synaptic devices: Materials, processing and applications
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC01211H
Abstract: This review focuses on recent development in artificial synaptic devices, including working principles, device structures, processing techniques, energy consumption, the functional materials of artificial synapses and applications.
Initial contact shapes the perception of friction
Publisher: Proceedings of the National Academy of Sciences
Date: 02-12-2021
Abstract: Humans have the remarkable ability to manipulate a large variety of objects, regardless of how fragile, heavy, or slippery they are. To correctly scale the grip forces, the nervous system gauges the slipperiness of the surface. This information is present at the instant we first touch an object, even before any lateral force develops. However, how friction could be estimated without slippage only from the fingertip skin deformation is not understood, either in neuroscience or engineering disciplines. This study demonstrates that a radial tensile strain of the skin is involved in the perception of slipperiness during this initial contact. These findings can inform the design of advanced tactile sensors for robotics or prosthetics and for improving haptic human–machine interactions.
Differential responses in populations of fingertip tactile afferents to objects' surface curvatures
Publisher: Wiley
Date: 10-1999
Spontaneous fluctuations in the peripheral photoplethysmographic waveform: Roles of arterial pressure and muscle sympathetic nerve activity
Publisher: American Physiological Society
Date: 02-2012
DOI: 10.1152/AJPHEART.00970.2011
Abstract: Assessment of spontaneous slow waves in the peripheral blood volume using the photoplethysmogram (PPG) has shown potential clinical value, but the physiological correlates of these fluctuations have not been fully elucidated. This study addressed the contribution of arterial pressure and muscle sympathetic nerve activity (MSNA) in beat-to-beat PPG variability in resting humans under spontaneous breathing conditions. Peripheral PPG waveforms were measured from the fingertip, earlobe, and toe in young and healthy in iduals ( n = 13), together with the arterial pressure waveform, electrocardiogram, respiration, and direct measurement of MSNA by microneurography. Cross-spectral coherence analysis revealed that among the PPG waveforms, low-frequency fluctuations (0.04–0.15 Hz) in the ear PPG had the highest coherence with arterial pressure (0.71 ± 0.15) and MSNA (0.44 ± 0.18, with a peak of 0.71 ± 0.16 at 0.10 ± 0.03 Hz). The normalized midfrequency powers (0.08–0.15 Hz), with an emphasis on the 0.1-Hz region, were positively correlated between MSNA and the ear PPG ( r = 0.77, P = 0.002). Finger and toe PPGs had lower coherence with arterial pressure (0.35 ± 0.10 and 0.30 ± 0.11, respectively) and MSNA (0.33 ± 0.10 and 0.26 ± 0.10, respectively) in the LF band but displayed higher coherence between themselves (0.54 ± 0.09) compared with the ear ( P 0.001), which may suggest the dominance of regional vasomotor activities and a common sympathetic influence in the glabrous skin. These findings highlight the differential mechanisms governing PPG waveform fluctuations across different body sites. Spontaneous PPG variability in the ear includes a major contribution from arterial pressure and MSNA, which may provide a rationale for its clinical utility.
Tactile sensory channels over-ruled by frequency decoding system that utilizes spike pattern regardless of receptor type
Publisher: eLife Sciences Publications, Ltd
Date: 06-08-2019
DOI: 10.7554/ELIFE.46510
Abstract: The established view is that vibrotactile stimuli evoke two qualitatively distinctive cutaneous sensations, flutter (frequencies 60 Hz) and vibratory hum (frequencies 60 Hz), subserved by two distinct receptor types (Meissner’s and Pacinian corpuscle, respectively), which may engage different neural processing pathways or channels and fulfil quite different biological roles. In psychological and physiological literature, those two systems have been labelled as Pacinian and non-Pacinian channels. However, we present evidence that low-frequency spike trains in Pacinian afferents can readily induce a vibratory percept with the same low frequency attributes as sinusoidal stimuli of the same frequency, thus demonstrating a universal frequency decoding system. We achieved this using brief low- litude pulsatile mechanical stimuli to selectively activate Pacinian afferents. This indicates that spiking pattern, regardless of receptor type, determines vibrotactile frequency perception. This mechanism may underlie the constancy of vibrotactile frequency perception across different skin regions innervated by distinct afferent types.
Classifying Torque, Normal Force and Direction Using Monkey Afferent Nerve Spike Rates
Publisher: Springer Berlin Heidelberg
Date: 2010
Generating tactile afferent stimulation patterns for slip and touch feedback in neural prosthetics
Publisher: IEEE
Date: 07-2013
Somatotopic mismatch following stroke: a pathophysiological condition escaping detection
Publisher: BMJ
Date: 06-10-2012
Tonic muscle pain does not increase fusimotor drive to human leg muscles: Implications for chronic muscle pain
Publisher: Wiley
Date: 11-03-2013
DOI: 10.1113/EXPPHYSIOL.2012.071670
Abstract: Experimental pain induced in animals has shown that noxious stimulation of group III and IV afferents increases the firing of muscle spindles via a reflex excitation of fusimotor (γ) motoneurones. Chronic muscle pain has been hypothesized to develop as a result of a vicious cycle involving this mechanism. In order to explore the effects of long-lasting muscle pain on the fusimotor system, single unit muscle spindle afferents were recorded from 15 subjects. Afferent activity was recorded from foot and ankle extensor muscles whilst infusing hypertonic saline into the tibialis anterior muscle of the ipsilateral leg, producing moderate-strong pain lasting for ∼60 min. A change in fusimotor drive was inferred by observing changes in the mean discharge rate of spontaneously active muscle spindle afferents. Homonymous and heteronymous muscles remained relaxed and showed no increase in activity, arguing against any fusimotor-driven increase in motor activity, and there was no net change in the firing of muscle spindle afferents. We conclude that long-lasting stimulation of group III and IV afferents fails to excite fusimotor neurones and increase muscle spindle discharge. Accordingly, the vicious cycle theory has no functional basis for the development of myalgia in human subjects.
Spike Timing Matters in Novel Neuronal Code Involved in Vibrotactile Frequency Perception
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.CUB.2017.04.011
Abstract: Skin vibrations sensed by tactile receptors contribute significantly to the perception of object properties during tactile exploration [1-4] and to sensorimotor control during object manipulation [5]. Sustained low-frequency skin vibration (<60 Hz) evokes a distinct tactile sensation referred to as flutter whose frequency can be clearly perceived [6]. How afferent spiking activity translates into the perception of frequency is still unknown. Measures based on mean spike rates of neurons in the primary somatosensory cortex are sufficient to explain performance in some frequency discrimination tasks [7-11] however, there is emerging evidence that stimuli can be distinguished based also on temporal features of neural activity [12, 13]. Our study's advance is to demonstrate that temporal features are fundamental for vibrotactile frequency perception. Pulsatile mechanical stimuli were used to elicit specified temporal spike train patterns in tactile afferents, and subsequently psychophysical methods were employed to characterize human frequency perception. Remarkably, the most salient temporal feature determining vibrotactile frequency was not the underlying periodicity but, rather, the duration of the silent gap between successive bursts of neural activity. This burst gap code for frequency represents a previously unknown form of neural coding in the tactile sensory system, which parallels auditory pitch perception mechanisms based on purely temporal information where longer inter-pulse intervals receive higher perceptual weights than short intervals [14]. Our study also demonstrates that human perception of stimuli can be determined exclusively by temporal features of spike trains independent of the mean spike rate and without contribution from population response factors.
Lateral Skin Stretch Influences Direction Judgments of Motion Across the Skin
Publisher: Springer Berlin Heidelberg
Date: 2014
Biphasic effects of tonic stimulation of muscle nociceptors on skin sympathetic nerve activity in human subjects
Publisher: Springer Science and Business Media LLC
Date: 06-07-2012
DOI: 10.1007/S00221-012-3156-Y
Abstract: Skin sympathetic nerve activity (SSNA) controls skin blood flow and sweat release, and acute noxious stimulation of skin has been shown to cause a decrease in SSNA in the anaesthetised or spinal cat. In awake human subjects, acute muscle pain causes a transient rise in SSNA, but the impact of long-lasting (tonic) stimulation of muscle nociceptors on skin sympathetic outflow, blood flow and sweat release is unknown. We tested the hypothesis that tonic stimulation of muscle nociceptors causes a sustained increase in sympathetic outflow to the skin. SSNA was recorded from the common peroneal nerve of 10 awake human subjects. Tonic muscle pain was induced by infusing hypertonic saline (7 %) into the tibialis anterior muscle over ~40 min, titrated to achieve a constant level of muscle pain. SSNA initially increased following the onset of the infusion, reaching a peak of 164 % of baseline within 5 min, but then showed a prolonged and sustained decrease, reaching a nadir of 77 % in 20 min. Conversely, skin blood flow (and vascular conductance) initially decreased, followed by a progressive increase there were no consistent changes in sweat release. In 9 of 10 subjects, SSNA and skin blood flow were inversely related. We conclude that sympathetic outflow to the skin exhibits a biphasic response to long-lasting stimulation of muscle nociceptors: an initial increase presumably related to the 'arousal' or 'alerting' component of pain, characterised by increased SSNA and decreased skin blood flow, followed by a prolonged decrease in SSNA and increased skin blood flow. The latter may be a purposeful response that contributes to wound healing.
Classification of Texture and Frictional Condition at Initial Contact by Tactile Afferent Responses
Publisher: Springer Berlin Heidelberg
Date: 2014
Peripheral Nerve Activation Evokes Machine-Learnable Signals in the Dorsal Column Nuclei
Publisher: Frontiers Media SA
Date: 20-03-2019
Perceived frequency of aperiodic vibrotactile stimuli depends on temporal encoding
Publisher: Springer International Publishing
Date: 2018
Memory at your fingertips: how viscoelasticity affects tactile neuron signaling
Publisher: eLife Sciences Publications, Ltd
Date: 05-09-2023
Movement Planning Determines Sensory Suppression: An Event-related Potential Study
Publisher: MIT Press - Journals
Date: 05-11-2021
DOI: 10.1162/JOCN_A_01747
Abstract: Sensory suppression refers to the phenomenon that sensory input generated by our own actions, such as moving a finger to press a button to hear a tone, elicits smaller neural responses than sensory input generated by external agents. This observation is usually explained via the internal forward model in which an efference copy of the motor command is used to compute a corollary discharge, which acts to suppress sensory input. However, because moving a finger to press a button is accompanied by neural processes involved in preparing and performing the action, it is unclear whether sensory suppression is the result of movement planning, movement execution, or both. To investigate this, in two experiments, we compared ERPs to self-generated tones that were produced by voluntary, semivoluntary, or involuntary button-presses, with externally generated tones that were produced by a computer. In Experiment 1, the semivoluntary and involuntary button-presses were initiated by the participant or experimenter, respectively, by electrically stimulating the median nerve in the participant's forearm, and in Experiment 2, by applying manual force to the participant's finger. We found that tones produced by voluntary button-presses elicited a smaller N1 component of the ERP than externally generated tones. This is known as N1-suppression. However, tones produced by semivoluntary and involuntary button-presses did not yield significant N1-suppression. We also found that the magnitude of N1-suppression linearly decreased across the voluntary, semivoluntary, and involuntary conditions. These results suggest that movement planning is a necessary condition for producing sensory suppression. We conclude that the most parsimonious account of sensory suppression is the internal forward model.
A point process approach to encode tactile afferents
Publisher: IEEE
Date: 04-2015
Somatotopic mismatch of hand representation following stroke: is recovery possible?
Publisher: Informa UK Limited
Date: 12-05-2016
DOI: 10.1080/13554794.2015.1046886
Abstract: Well-organized somatotopic representation of the hand is required to interpret input from cutaneous mechanoreceptors. Previous reports have identified patients with various distortions of somatotopic representation after stroke. Importantly, those patients were investigated years after the stroke, indicating that afferent signal regained access to the cortical circuits however, further plastic changes, which would re-establish somatotopic order and ability to correctly localize tactile stimuli, did not follow. Thus, it was not known whether somatotopic organization could be restored in such patients and whether there is a potential for new rehabilitation strategies. This is the first case report demonstrating normalization of somatotopic representation.
Individual differences in the cardiovascular responses to tonic muscle pain: Parallel increases or decreases in muscle sympathetic nerve activity, blood pressure and heart rate
Publisher: Wiley
Date: 28-08-2012
DOI: 10.1113/EXPPHYSIOL.2012.066191
Abstract: We recently showed that acute muscle pain, induced by bolus intramuscular injection of hypertonic saline, causes a sustained increase in muscle sympathetic nerve activity (MSNA) and a modest increase in blood pressure and heart rate. However, it is not known whether long-lasting (tonic) pain, which more closely resembles chronic pain, causes a sustained increase in MSNA and blood pressure. We tested this hypothesis by recording MSNA in 12 healthy subjects. Tonic pain was induced for ~60 min by slow intramuscular infusion of hypertonic saline (7%) into the ipsilateral tibialis anterior muscle. Pain was sustained at a tolerable level (5/10 to 6/10 on a visual analog scale). Seven subjects showed progressive increases in mean MSNA litude during tonic pain, increasing to 154 ± 17% (SEM) at 45 min and remaining essentially constant for the duration of the infusion. In these subjects, blood pressure and heart rate also increased. Conversely, for the other five subjects MSNA showed a progressive decline, with a peak fall of 67 ± 11% at 40 min blood pressure and heart rate also fell in these subjects. We conclude that tonic muscle pain has long-lasting effects on the sympathetic control of blood pressure, causing a sustained increase in some subjects yet a sustained decrease in others. This may have implications for in idual differences in the cardiovascular consequences of chronic pain.
Friction sensing mechanisms for perception and motor control: passive touch without sliding may not provide perceivable frictional information
Publisher: American Physiological Society
Date: 03-2021
Abstract: This study contributes to understanding how frictional information is obtained and used by the brain. When the skin is contacting surfaces of identical topography but varying frictional properties, the deformation pattern is different however, available sensory cues did not get translated into perception of frictional properties unless a sufficiently large lateral movement was present. These neurophysiological findings may inform how to design and operate haptic devices relying on friction modulation principles.
The tactile motion aftereffect suggests an intensive code for speed in neurons sensitive to both speed and direction of motion
Publisher: American Physiological Society
Date: 03-2016
Abstract: Neurophysiological studies in primates have found that direction-sensitive neurons in the primary somatosensory cortex (SI) generally increase their response rate with increasing speed of object motion across the skin and show little evidence of speed tuning. We employed psychophysics to determine whether human perception of motion direction could be explained by features of such neurons and whether evidence can be found for a speed-tuned process. After adaptation to motion across the skin, a subsequently presented dynamic test stimulus yields an impression of motion in the opposite direction. We measured the strength of this tactile motion aftereffect (tMAE) induced with different combinations of adapting and test speeds. Distal-to-proximal or proximal-to-distal adapting motion was applied to participants' index fingers using a tactile array, after which participants reported the perceived direction of a bidirectional test stimulus. An intensive code for speed, like that observed in SI neurons, predicts greater adaptation (and a stronger tMAE) the faster the adapting speed, regardless of the test speed. In contrast, speed tuning of direction-sensitive neurons predicts the greatest tMAE when the adapting and test stimuli have matching speeds. We found that the strength of the tMAE increased monotonically with adapting speed, regardless of the test speed, showing no evidence of speed tuning. Our data are consistent with neurophysiological findings that suggest an intensive code for speed along the motion processing pathways comprising neurons sensitive both to speed and direction of motion.
Tactile Motion Adaptation Reduces Perceived Speed but Shows No Evidence of Direction Sensitivity
Publisher: Public Library of Science (PLoS)
Date: 24-09-2012
Control of forces applied by individual fingers engaged in restraint of an active object
Publisher: American Physiological Society
Date: 07-1997
Abstract: Burstedt, Magnus K. O., Ingvars Birznieks, Benoni B. Edin, and Roland S. Johansson. Control of forces applied by in idual fingers engaged in restraint of an active object. J. Neurophysiol. 78: 117–128, 1997. 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 in idual 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.
The effects of preferential A- and C-fibre blocks and T-type calcium channel antagonist on detection of low-force monofilaments in healthy human participants.
Publisher: Springer Science and Business Media LLC
Date: 13-08-2015
Tactile Sensors for Friction Estimation and Incipient Slip Detection—Toward Dexterous Robotic Manipulation: A Review
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-11-2018
Single tactile afferents outperform human subjects in a vibrotactile intensity discrimination task
Publisher: American Physiological Society
Date: 15-11-2014
Abstract: We simultaneously compared the sensitivity of single primary afferent neurons supplying the glabrous skin of the hand and the psychophysical litude discrimination thresholds in human subjects for a set of vibrotactile stimuli delivered to the receptive field. All recorded afferents had a dynamic range narrower than the range of litudes across which the subjects could discriminate. However, when the vibration litude was chosen to be within the steepest part of the afferent's stimulus-response function the response of single afferents, defined as the spike count over the vibration duration (500 ms), was often more sensitive in discriminating vibration litude than the perceptual judgment of the participants. We quantified how the neuronal performance depended on the integration window: for short windows the neuronal performance was inferior to the performance of the subject. The neuronal performance progressively improved with increasing spike count duration and reached a level significantly above that of the subjects when the integration window was 250 ms or longer. The superiority in performance of in idual neurons over observers could reflect a nonoptimal integration window or be due to the presence of noise between the sensory periphery and the cortical decision stage. Additionally, it could indicate that the range of perceptual sensitivity comes at the cost of discrimination through pooling across neurons with different response functions.
Muscle spindles in human tibialis anterior encode muscle fascicle length changes
Publisher: American Physiological Society
Date: 04-2017
Abstract: Muscle spindles provide exquisitely sensitive proprioceptive information regarding joint position and movement. Through passively driven length changes in the muscle-tendon unit (MTU), muscle spindles detect joint rotations because of their in-parallel mechanical linkage to muscle fascicles. In human microneurography studies, muscle fascicles are assumed to follow the MTU and, as such, fascicle length is not measured in such studies. However, under certain mechanical conditions, compliant structures can act to decouple the fascicles, and, therefore, the spindles, from the MTU. Such decoupling may reduce the fidelity by which muscle spindles encode joint position and movement. The aim of the present study was to measure, for the first time, both the changes in firing of single muscle spindle afferents and changes in muscle fascicle length in vivo from the tibialis anterior muscle (TA) during passive rotations about the ankle. Unitary recordings were made from 15 muscle spindle afferents supplying TA via a microelectrode inserted into the common peroneal nerve. Ultrasonography was used to measure the length of an in idual fascicle of TA. We saw a strong correlation between fascicle length and firing rate during passive ankle rotations of varying rates (0.1–0.5 Hz) and litudes (1–9°). In particular, we saw responses observed at relatively small changes in muscle length that highlight the sensitivity of the TA muscle to small length changes. This study is the first to measure spindle firing and fascicle dynamics in vivo and provides an experimental basis for further understanding the link between fascicle length, MTU length, and spindle firing patterns. NEW & NOTEWORTHY Muscle spindles are exquisitely sensitive to changes in muscle length, but recordings from human muscle spindle afferents are usually correlated with joint angle rather than muscle fascicle length. In this study, we monitored both muscle fascicle length and spindle firing from the human tibialis anterior muscle in vivo. Our findings are the first to measure these signals in vivo and provide an experimental basis for exploring this link further.
Perceived tactile intensity at a fixed primary afferent spike rate varies with the temporal pattern of spikes
Publisher: American Physiological Society
Date: 10-2022
Abstract: The perceived intensity of a vibrotactile stimulus is thought to depend on single-neuron firing rates (rate coding) and the number of active afferents (population coding). Unaddressed until now is whether the temporal relation of in idual spikes also conveys information about tactile intensity. We used cutaneous electro-tactile stimulation to investigate how the temporal structure of a fixed number of spikes in a 1-s train influenced the perception of intensity. Four mean spike rates spanning the flutter and vibratory hum range (36 Hz, 60 Hz 120 Hz, 180 Hz) were tested, with spikes grouped into a regular pattern, or bursts of 2-6 spikes spaced 3 ms apart. To link a putative neural code to perception, perceived intensity was assessed in 16 human participants (aged 20-45 4 females) using the psychophysical paradigm of magnitude estimation. Compound sensory nerve action potentials were recorded to assess any stimulus variation in afferent recruitment. The temporal structuring of a fixed number of spikes into periodic bursts of multiple spikes altered perceived intensity as a function of burst spike count. The largest increase was seen at 36 Hz, where the bursts of six spikes were rated 2.1 times stronger than the regularly spaced spikes [95% confidence interval (CI): 1.9-2.3]. The true increase is likely larger as temporal structuring of spikes into bursts had some negative effect on afferent recruitment. We conclude that the perceived intensity can be modulated by changing temporal features of afferent discharge even when normalized for the number of recruited afferents. NEW & NOTEWORTHY Structuring a fixed number of spikes into temporal burst patterns evoke gradations of perceived intensity with burst spike count, emphasizing the importance of spike timing in primary afferents for shaping perception. This forms the basis for new strategies in communicating a range of intensity information to users of neural interfaces by simply varying the timing of spikes in nonspecific primary afferents using fixed-charge electric pulses, without requiring alterations in stimulation current or mean pulse frequency.
Temporal patterns in electrical nerve stimulation: burst gap code shapes tactile frequency perception
Publisher: Cold Spring Harbor Laboratory
Date: 10-04-2020
DOI: 10.1101/2020.04.10.033241
Abstract: We have previously described a novel temporal encoding mechanism in the somatosensory system, where mechanical pulses grouped into periodic bursts create a perceived tactile frequency based on the duration of the silent gap between bursts, rather than the mean rate or the periodicity. This coding strategy may offer new opportunities for transmitting information to the brain using various sensory neural prostheses and haptic interfaces. However, it was not known whether the same coding mechanisms apply when using electrical stimulation, which recruits a different spectrum of afferents. Here, we demonstrate that the predictions of the burst gap coding model for frequency perception apply to burst stimuli delivered with electrical pulses, re-emphasising the importance of the temporal structure of spike patterns in neural processing and perception of tactile stimuli. Reciprocally, the electrical stimulation data confirm that the results observed with mechanical stimulation do indeed depend on neural processing mechanisms in the central nervous system, and are not due to skin mechanical factors and resulting patterns of afferent activation.
Decoding tactile sensation: Multiple regression analysis of monkey fingertip afferent mechanoreceptor population responses
Publisher: IEEE
Date: 08-2012
How Tactile Afferents in the Human Fingerpad Encode Tangential Torques Associated with Manipulation: Are Monkeys Better than Us?
Publisher: Society for Neuroscience
Date: 04-05-2023
DOI: 10.1523/JNEUROSCI.1305-22.2023
Abstract: Dexterous object manipulation depends critically on information about forces normal and tangential to the fingerpads, and also on torque associated with object orientation at grip surfaces. We investigated how torque information is encoded by human tactile afferents in the fingerpads and compared them to 97 afferents recorded in monkeys ( n = 3 2 females) in our previous study. Human data included slowly-adapting Type-II (SA-II) afferents, which are absent in the glabrous skin of monkeys. Torques of different magnitudes (3.5–7.5 mNm) were applied in clockwise and anticlockwise directions to a standard central site on the fingerpads of 34 human subjects (19 females). Torques were superimposed on a 2, 3, or 4 N background normal force. Unitary recordings were made from fast-adapting Type-I (FA-I, n = 39), and slowly-adapting Type-I (SA-I, n = 31) and Type-II (SA-II, n = 13) afferents supplying the fingerpads via microelectrodes inserted into the median nerve. All three afferent types encoded torque magnitude and direction, with torque sensitivity being higher with smaller normal forces. SA-I afferent responses to static torque were inferior to dynamic stimuli in humans, while in monkeys the opposite was true. In humans this might be compensated by the addition of sustained SA-II afferent input, and their capacity to increase or decrease firing rates with direction of rotation. We conclude that the discrimination capacity of in idual afferents of each type was inferior in humans than monkeys which could be because of differences in fingertip tissue compliance and skin friction. SIGNIFICANCE STATEMENT We investigated how in idual human tactile nerve fibers encode rotational forces (torques) and compared them to their monkey counterparts. Human hands, but not monkey hands, are innervated by a tactile neuron type (SA-II afferents) specialized to encode directional skin strain yet, so far, torque encoding has only been studied in monkeys. We find that human SA-I afferents were generally less sensitive and less able to discriminate torque magnitude and direction than their monkey counterparts, especially during the static phase of torque loading. However, this shortfall in humans could be compensated by SA-II afferent input. This indicates that variation in afferent types might complement each other signaling different stimulus features possibly providing computational advantage to discriminate stimuli.
Consistent interindividual increases or decreases in muscle sympathetic nerve activity during experimental muscle pain
Publisher: Springer Science and Business Media LLC
Date: 31-01-2014
DOI: 10.1007/S00221-014-3847-7
Abstract: We recently showed that long-lasting muscle pain, induced by intramuscular infusion of hypertonic saline, evoked two patterns of cardiovascular responses across subjects: one group showed parallel increases in muscle sympathetic nerve activity (MSNA), blood pressure, and heart rate, while the other group showed parallel decreases. Given that MSNA is consistent day to day, we tested the hypothesis that in iduals who show increases in MSNA during experimental muscle pain will show consistent responses over time. MSNA was recorded from the peroneal nerve, together with blood pressure and heart rate, during an intramuscular infusion of hypertonic saline causing pain for an hour in 15 subjects on two occasions, 2-27 weeks apart. Pain intensity ratings were not significantly different between the first (5.8 ± 0.4/10) and second (6.1 ± 0.2) recording sessions. While four subjects showed significant decreases in the first session (46.6 ± 9.2% of baseline) and significant increases in the second (159.6 ± 8.9%), in 11 subjects, there was consistency in the changes in MSNA over time: either a sustained decrease (55.6 ± 6.8%, n = 6) or a sustained increase (143.5 ± 6.1%, n = 5) occurred in both recording sessions. There were no differences in pain ratings between sessions for any subjects. We conclude that the changes in MSNA during long-lasting muscle pain are consistent over time in the majority of in iduals, reflecting the importance of studying interin idual differences in physiology.
The effects of experimental muscle and skin pain on the static stretch sensitivity of human muscle spindles in relaxed leg muscles
Publisher: Wiley
Date: 06-2008
Temporal integration of tactile inputs from multiple sites
Publisher: Springer International Publishing
Date: 2016
Directional encoding of fingertip force by human tactile afferents
Publisher: Wiley
Date: 10-1999
Tactile afferents encode grip safety before slip for different frictions
Publisher: IEEE
Date: 08-2014
The Relationship Between Tactile Intensity Perception and Afferent Spike Count is Moderated by a Function of Frequency
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2022
Effects of deep and superficial experimentally induced acute pain on muscle sympathetic nerve activity in human subjects
Publisher: Wiley
Date: 2009
Initial contact shapes the perception of friction
Publisher: Cold Spring Harbor Laboratory
Date: 22-09-2021
DOI: 10.1101/2021.09.20.461039
Abstract: Humans efficiently estimate the grip force necessary to lift a variety of objects, including slippery ones. The regulation of grip force starts with the initial contact, and takes into account the surface properties, such as friction. This estimation of the frictional strength has been shown to depend critically on cutaneous information. However, the physical and perceptual mechanism that provides such early tactile information remains elusive. In this study, we developed a friction-modulation apparatus to elucidate the effects of the frictional properties of objects during initial contact. We found a correlation between participants’ conscious perception of friction and radial strain patterns of skin deformation. The results provide insights into the tactile cues made available by contact mechanics to the sensorimotor regulation of grip, as well as to the conscious perception of the frictional properties of an object.
Effects of changing skin mechanics on the differential sensitivity to surface compliance by tactile afferents in the human finger pad
Publisher: American Physiological Society
Date: 10-2015
Abstract: It is not known how changes in skin mechanics affect the responses of cutaneous mechanoreceptors in the finger pads to compression forces. We used venous occlusion to change the stiffness of the fingers and investigated whether this influenced the firing of low-threshold mechanoreceptors to surfaces of differing stiffness. Unitary recordings were made from 10 slowly adapting type I (SAI), 10 fast adapting type I (FAI) and 9 slowly adapting type II (SAII) units via tungsten microelectrodes inserted into the median nerve at the wrist. A servo-controlled stimulator applied r -and-hold forces (1, 2, and 4 N) at a constant loading and unloading rate (2 N/s) via a flat 2.5-cm-diameter silicone disk over the center of the finger pad. Nine silicone disks (objects), varying in compliance, were used. Venous occlusion, produced by inflating a sphygmomanometer cuff around the upper arm to 40 ± 5 mmHg, was used to induce swelling of the fingers and increase the compliance of the finger pulp. Venous occlusion had no effect on the firing rates of the SAI afferents, nor on the slopes of the relationship between mean firing rate and object compliance at each litude, but did significantly reduce the slopes for the FAI afferents. Although the SAII afferents possess a poor capacity to encode changes in object compliance, mean firing rates were significantly lower during venous occlusion. The finding that venous occlusion had no effect on the firing properties of SAI afferents indicates that these afferents preserve their capacity to encode changes in object compliance, despite changes in skin mechanics.
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