Document Detail


Population estimates for responses of cutaneous mechanoreceptors to a vertically indenting probe on the glabrous skin of monkeys.
MedLine Citation:
PMID:  8335066     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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 afferents 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 response 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 stimulation of the RF center. Thus, the coding capacity of the population extends the range of tactile discriminability. The slope and range of stimulus-response functions for populations was enhanced relative to responses to on-center stimulation. This occurs because of recruitment of afferents with RF centers adjacent to and remote from the stimulus, depending upon thresholds and receptive field sizes for different stimulus parameters. With stimulation at increasing rates and forces, there is a progressive spatial recruitment of receptors.(ABSTRACT TRUNCATED AT 400 WORDS)
Authors:
R H Cohen; C J Vierck
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Experimental brain research     Volume:  94     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  1993  
Date Detail:
Created Date:  1993-08-20     Completed Date:  1993-08-20     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  105-19     Citation Subset:  IM; S    
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MeSH Terms
Descriptor/Qualifier:
Action Potentials / physiology
Animals
Brain Mapping
Hand / anatomy & histology,  innervation,  physiology
Macaca mulatta
Mechanoreceptors / physiology*
Nerve Fibers / physiology
Neurons, Afferent / physiology
Physical Stimulation
Recruitment, Neurophysiological
Skin / innervation
Skin Physiological Phenomena*
Touch / physiology
Grant Support
ID/Acronym/Agency:
NIMH MH 15735/MH/NIMH NIH HHS; NINCDS NS 07261/NS/NINDS NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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