Mechanoreceptive afferents in the human sural nerve (original) (raw)
Related papers
Journal of Neurophysiology, 2018
Cutaneous afferents convey exteroceptive information about the interaction of the body with the environment and proprioceptive information about body position and orientation. Four classes of low-threshold mechanoreceptor afferents innervate the foot sole and transmit feedback that facilitates the conscious and reflexive control of standing balance. Experimental manipulation of cutaneous feedback has been shown to alter the control of gait and standing balance. This has led to a growing interest in the design of intervention strategies that enhance cutaneous feedback and improve postural control. The advent of single-unit microneurography has allowed the firing and receptive field characteristics of foot sole cutaneous afferents to be investigated. In this review, we consolidate the available cutaneous afferent microneurographic recordings from the foot sole and provide an analysis of the firing threshold, and receptive field distribution and density of these cutaneous afferents. Th...
Experimental Brain Research, 1990
The responses of non-cutaneous receptors in the human hand to normal digit movements were studied using single afferent recordings from the radial nerve. Eight joint-related afferents had thresholds of 50 mN or less. All responded to passive flexion movements within the physiological range of joint rotation and showed predominantly static response sensitivity; none increased its discharge during passive extension. However, only two of these eight afferents showed the same response pattern during active movements; three discharged only during the extension phase whereas the other three discharged both during extension and flexion. No highthreshold, joint-related mechanoreceptive afferents were encountered in a population of 148 afferents recorded from the cutaneous portion of the radial nerve indicating a scarcity of such afferents on the dorsal aspect of finger joints. Seven high-threshold, subcutaneous mechanoreceptive units not related to joints had thresholds for indentations of 50 mN or more and lacked responses to finger movements. Low-threshold mechanoreceptive afferents related to joints in the human hand may thus provide kinematic information in the physiological midrange of both passive and active movements. Joint position cannot, however, be derived unambiguously from their discharge since the receptor responses may be dramatically altered by muscle activity.
Properties of cutaneous mechanoreceptors in the human hand - related to touch sensation
Recordings from single peripheral nerve fibres made it possible to analyse the functional properties of tac-tile afferent units supplying the glabrous skin of the human hand and to assess directly the relation between impulse discharge and perceptive experiences. The 17,000 tactile units in this skin area of the human hand are of four different types: two fast adapting types, FA I and FA I1 (formerly RA and PC), and two slowly adapting types, SA I and SA 11. The receptive field characteristics and the densities in the skin of the type I units (FA I and SA I) indicate that these account for the detailed spatial resolution that is of paramount importance for the motor skill and the explorative role of the hand. The relationship between the stimulus amplitude and perceived intensity during sustained skin indentations did not match the corresponding stimulus response functions of SA units suggesting non-linear transformations within the central nervous system. These transformations, in turn, appear to vary between subjects. A single impulse in a single FA I unit may be felt when originating from the most important tactile regions of the hand, indicating that the psychophysical detection may be set by the threshold of the sense organs. Moreover, no significant noise seems to be superimposed in the respective central sensory pathways.
Properties of human skin mechanoreceptors in peripheral neuropathy
Clinical Neurophysiology, 2002
Objectives: To investigate the properties of mechanoreceptors in patients with peripheral neuropathy. The skin mechanoreceptor is a terminal organ of the primary sensory neuron, which is likely to be affected earlier and more severely than is the nerve trunk by peripheral neuropathies.
Journal of neurophysiology, 2017
Single unit microneurography was used to record the firing characteristics of the four classes of foot sole cutaneous afferents (fast and slowly adapting type I and II; FAI, FAII, SAI, SAII) in response to sinusoidal vibratory stimuli. Frequency (3-250Hz) and amplitude (0.001-2mm) combinations were applied to afferent receptive fields through a 6mm diameter probe. The impulses per cycle, defined as the number of action potentials evoked per vibration sine wave, were measured over one second of vibration at each frequency-amplitude combination tested. Afferent entrainment threshold (lowest amplitude at which an afferent could entrain 1:1 to the vibration frequency) and afferent firing threshold (minimum amplitude for which impulses per cycle was greater than zero) were then obtained for each frequency. Increases in vibration frequency are generally associated with decreases in expected impulses per cycle (p < 0.001), but each foot sole afferent class appears uniquely tuned to vibr...
Journal of Neurophysiology, 2012
We have shown for the first time that single cutaneous afferents in the foot dorsum have significant reflex coupling to motoneurons supplying muscles in the upper limb, particularly posterior deltoid and triceps brachii. These observations strengthen what we know from whole nerve stimulation, that skin on the foot and ankle can contribute to the modulation of interlimb muscles in distant innervation territories. The current work provides evidence of the mechanism behind the reflex, where one single skin afferent can evoke a reflex response, rather than a population. Nineteen of forty-one (46%) single cutaneous afferents isolated in the dorsum or plantar surface of the foot elicited a significant modulation of muscle activity in the upper limb. Identification of single afferents in this reflex indicates the strength of the connection and, ultimately, the importance of foot skin in interlimb coordination. The median response magnitude was 2.29% of background EMG, and the size of the e...
Experimental Brain Research, 1993
Recordings were obtained from low-threshold mechanoreceptive afferents during stimulation with a 0.5-mm-diameter probe at the receptive field (RF) center and at different distances from the point of maximal sensitivity. At each location, force-controlled stimuli of 0.5-4.0 g were ramped on to a plateau and then off at rates of 1, 10, and 100 g/s. The properties of rapidly adapting (RA) and slowly adapting type I (SAI) mechanoreceptors, when stimulated at the RF center, were similar in many respects to those reported in previous studies. Controlled stimulation away from the RF centers revealed that RF size for RAs was primarily dependent upon ramp rate, and for SAIs the size of the RF was primarily dependent upon load (force). The action potentials from individual afferents during stimulation at each location were binned in time and assigned to spatial segments of 1 mm. These responses were multiplied by: (A) an annular area of the receptive field and (B) the innervation density for the afferent type and skin region. The calculations provided estimates of overall rates of activity among the population of cutaneous afferents that respond to indentation by a small probe. Important differences were obtained between the responses of the population of afterents activated by the trapezoidal stimulus and the responses of afferents stimulated only at the RF center. Populations of tactile afferents provide more information for rate and intensity (force) discriminations than is available from units stimulated at the RF center. For RA afferents, the exponent of the power function describing relationships between stimulus rate and the population discharge (in impulses per second) was 0.3 times greater than the exponent for responses to on-center stimulation. For SAI mechanoreceptors, the exponent of the power functions for static responses to force was 0.22 times greater for the population responses than for on-center activation. Population functions for RA responses to the rate of force application and for SAI responses to static load saturated less than comparable responses to stimu-Correspondence to: C.J. Vierck 106 fore, the relative magnitudes of onset, offset, and steadystate sensations elicited by stimulation at different rates and locations should vary systematically, according to the absolute and relative densities of each receptor type.
Responses in glabrous skin mechanoreceptors during precision grip in humans
Experimental Brain Research, 1987
Impulses in single tactile units innervating the human glabrous skin were recorded percutaneously from the median nerve using tungsten electrodes. The units were classified as belonging to one of the four categories: fast adapting with small receptive fields (FA I), fast adapting with large receptive fields (FA II), slowly adapting with small fields (SA I), and slowly adapting with large fields (SAII). A small test object was lifted, positioned in space and replaced using the precision grip between fingers and thumb. The grip force, the load force (vertical lifting force), the vertical movements of the object and vibrations (accelerations) in the object were recorded. After being virtually silent between lifts, the FA I units whose fields contacted the object became highly active during the initial period of grip force increase (initial response). This was also true possible implications for the control of precise manipulative movements.
Clinical Anatomy, 2005
The present study attempts to determine the cutaneous pattern of distribution of the sural nerve on the dorsum of the foot to note the predominant pattern present and whether there was any association between the innervation pattern and sex or side. A total of 260 Indian feet (78 adult feet: 60 male, 18 female; 52 fetal feet: 20 male, 32 female) were dissected. The results showed six patterns of innervation of the toes by the sural nerve. In Type I, the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 2nd, 3rd, 4th, and 5th toes by the superficial peroneal nerve alone (35.38%). In Type II the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 4th and 5th toes by the sural nerve along with the superficial peroneal nerve (10%). In Type III the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 3rd, 4th, and 5th toes by the sural nerve along with the superficial peroneal nerve (21.15%). In Type IV the lateral 1½ toes were supplied by the sural nerve alone and the adjacent sides of the 3rd and 4th toes by the superficial peroneal nerve alone (3.85%). In Type V the lateral 1½ toes were supplied by the sural nerve alone and the adjacent sides of the 3rd and 4th toes were supplied by the sural nerve along with the superficial peroneal nerve (5%). In Type VI the lateral 2½ toes were supplied by the sural nerve alone (24.61%). The predominant patterns were Type I (35.38%), Type VI (24.61%), and Type III (21.15%). There was no association between the innervation pattern of the sural nerve and sex or side. The pattern, which is usually described, was found in only 35.38% of feet. Considering the variation in the pattern of cutaneous distribution of the sural nerve in Indian feet, the function of the sural nerve may be to supply a wider area of skin than is usually described.