Modulation of ongoing EMG by different classes of low-threshold mechanoreceptors in the human hand

McNulty, Penelope A.; Macefield, Vaughan G.

doi:10.1111/j.1469-7793.2001.01021.x

Cited by 21 publications

(25 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using the same approach, our laboratory has recently shown that in the hand, as in the leg, the synaptic strength of individual muscle spindle afferents is so weak that it cannot be identified using spike-triggered averaging of EMG (McNulty and Macefield 2001). However, we have also shown that individual low-threshold mechanoreceptors in the glabrous skin of the hand can cause reflex modulation of EMG of the muscles acting on the digits (McNulty and Macefield 2001;McNulty et al 1999).…”

Section: Introductionmentioning

confidence: 81%

“…However, we have also shown that individual low-threshold mechanoreceptors in the glabrous skin of the hand can cause reflex modulation of EMG of the muscles acting on the digits (McNulty and Macefield 2001;McNulty et al 1999). Less than half of all the cutaneous mechanoreceptors exhibited any reflex coupling, with reflex coupling limited to the rapidly adapting type I (FA I), rapidly adapting type II (FA II), and slowly adapting type II (SA II) mechanoreceptors.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evidence for Strong Synaptic Coupling Between Single Tactile Afferents From the Sole of the Foot and Motoneurons Supplying Leg Muscles

Fallon

Bent²,

McNulty³

et al. 2005

Journal of Neurophysiology

119

101

View full text Add to dashboard Cite

Evidence for strong synaptic coupling between single tactile afferents from the sole of the foot and motoneurons supplying leg muscles. J Neurophysiol 94: 3795-3804, 2005. First published August 3, 2005 doi:10.1152/jn.00359.2005. It has been known for some time that populations of cutaneous and muscle afferents can provide short-latency facilitation of motoneuron pools. Recently, it has been shown that the input from individual low-threshold mechanoreceptors in the glabrous skin of the hand can modulate ongoing activity in muscles acting on the fingers via spinally mediated pathways. We have extended this work to examine whether such strong synaptic coupling exists between tactile afferents in the sole of the foot and motoneurons supplying muscles that act about the ankle. We recorded from 53 low-threshold mechanoreceptors in the glabrous skin of the foot via microelectrodes inserted percutaneously into the tibial nerve of awake human subjects. Reflex modulation of ongoing whole muscle electromyography (EMG) was observed for each of the four classes of low-threshold cutaneous mechanoreceptors (17 of 21 rapidly adapting type I; 2 of 4 rapidly adapting type II; 7 of 18 slowly adapting type I; and 4 of 10 slowly adapting type II). Reflex modulation of the firing probability in single motor units (5 of 11) was also observed. These results indicate that strong synaptic coupling between tactile afferents and spinal motoneurons is not a specialization of the hand and emphasizes the potential importance of cutaneous inputs from the sole of the foot in the control of gait and posture.

show abstract

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Evidence for Strong Synaptic Coupling Between Single Tactile Afferents From the Sole of the Foot and Motoneurons Supplying Leg Muscles

Fallon

Bent²,

McNulty³

et al. 2005

Journal of Neurophysiology

119

101

View full text Add to dashboard Cite

show abstract

“…This may be particularly evident in women or men with smaller fingers where the more densely packed receptors have been suggested to improve acuity (Peters et al 2009). Second, Merkel receptors have the highest acuity (Phillips et al 1990) but are the only lowthreshold receptors in the glabrous skin of the hand for which a role in fine motor control could not be demonstrated (McNulty et al 1999;McNulty and Macefield 2001). This suggests that Merkel receptors may have stronger connections to the somatosensory cortex than other low-threshold mechanoreceptors and so provide a learnt attentional focus to cutaneous inputs (McNulty and Macefield 2001).…”

Section: Changes Across the Handmentioning

confidence: 99%

Age-related changes in cutaneous sensation in the healthy human hand

Bowden

McNulty

2012

AGE

View full text Add to dashboard Cite

Cutaneous sensation deteriorates with age. It is not known if this change is consistent over the entire hand or if sensation is affected by changes in skin mechanics. Cutaneous perceptual thresholds were tested at eight sites in the glabrous skin and two in the hairy skin of both hands in 70 subjects (20-88 years), five male and five female per decade, using calibrated von Frey filaments, two-point discrimination, and texture discrimination. Venous occlusion at the wrist (40±10 mmHg) and moisturizer were used to alter skin mechanics. Cutaneous thresholds increased significantly with age (p<0.001); von Frey thresholds were 0.04 g [0.02-0.07] (median and interquartile range) in the 20s and 0.16 g [0.04-0.4] in the 80s, with differences between hands for older females (p00.044) but not males. The pattern of changes in cutaneous sensation varied according to the site tested with smaller changes on the fingers compared to the palm. Two-point discrimination deteriorated with age (p00.046), but with no interaction between sex, handedness, or changes in skin mechanics. There were no significant differences for texture discrimination. Changes in skin mechanics improved cutaneous thresholds in the oldest males after moisturizing (p00.001) but not otherwise. These results emphasize the complex pattern of age-related deterioration in cutaneous sensation with differences between sexes, the hands, sites on the hand, and the mode of testing. As the index fingertip is not a sensitive indicator of sensory decline, the minimum assessment of age-related changes in cutaneous sensation should include both hands, and sites on the palm.

show abstract

“…For example, in contrast to all other types of tactile afferents innervating the human glabrous skin, selective intraneural stimulation of single SA-II afferents does not evoke a percept (Torebjörk et al, 1987;Macefield et al, 1990). Likewise, impulses in SA-II afferents, including SA-IInail afferents, can influence automatically ongoing EMG in muscles acting on the digits through spinal pathways (McNulty et al, 1999;McNulty and Macefield, 2001). It is also possible that the tonic impulse activity in SA-IInail afferents, which is not consciously perceived, contribute to upholding digit representations in the central somatosensory system, which apparently requires continuous peripheral input (Kelahan and Doetsch, 1984;Tweedale, 1988, 1991).…”

Section: What Do the Sa-iinail Afferents Tell The Cns?mentioning

confidence: 99%

Slowly Adapting Mechanoreceptors in the Borders of the Human Fingernail Encode Fingertip Forces

Birznieks¹,

Macefield²,

Westling³

et al. 2009

J. Neurosci.

Self Cite

View full text Add to dashboard Cite

There are clusters of slowly adapting (SA) mechanoreceptors in the skin folds bordering the nail. These "SA-IInail" afferents, which constitute nearly one fifth of the tactile afferents innervating the fingertip, possess the general discharge characteristics of slowly adapting type II (SA-II) tactile afferents located elsewhere in the glabrous skin of the human hand. Little is known about the signals in the SA-IInail afferents when the fingertips interact with objects. Here we show that SA-IInail afferents reliably respond to fingertip forces comparable to those arising in everyday manipulations. Using a flat stimulus surface, we applied forces to the finger pad while recording impulse activity in 17 SA-IInail afferents. Ramp-and-hold forces (amplitude 4 N, rate 10 N/s) were applied normal to the skin, and at 10, 20, or 30°f rom the normal in eight radial directions with reference to the primary site of contact (25 force directions in total). All afferents responded to the force stimuli, and the responsiveness of all but one afferents was broadly tuned to a preferred direction of force. The preferred directions among afferents were distributed all around the angular space, suggesting that the population of SA-IInail afferents could encode force direction. We conclude that signals in the population of SA-IInail afferents terminating in the nail walls contain vectorial information about fingertip forces. The particular tactile features of contacted surfaces would less influence force-related signals in SA-IInail afferents than force-related signals present in afferents terminating in the volar skin areas that directly contact objects.

show abstract

Modulation of ongoing EMG by different classes of low-threshold mechanoreceptors in the human hand

Cited by 21 publications

References 63 publications

Evidence for Strong Synaptic Coupling Between Single Tactile Afferents From the Sole of the Foot and Motoneurons Supplying Leg Muscles

Evidence for Strong Synaptic Coupling Between Single Tactile Afferents From the Sole of the Foot and Motoneurons Supplying Leg Muscles

Age-related changes in cutaneous sensation in the healthy human hand

Slowly Adapting Mechanoreceptors in the Borders of the Human Fingernail Encode Fingertip Forces

Contact Info

Product

Resources

About