ANTERIOR PARIETAL CORTICAL RESPONSE TO TACTILE AND SKIN-HEATING STIMULI
APPLIED TO THE SAME SKIN SITE.
Tommerdahl, M., K. A. Delemos, C. J. Vierck, O. V. Favorov and B. L. Whitsel.
Departments of Biomedical Engineering and Physiology, and Dental Research
Center, University of North Carolina at Chapel Hill, Chapel Hill, North
Carolina 27599 and Department of Neuroscience, University of Florida,
Gainesville, FL 32610.
APStracts 3:0062N, 1996.
SUMMARY AND CONCLUSIONS
1. The response of anterior parietal cortex to skin stimuli was evaluated with
optical intrinsic signal imaging and extracellular microelectrode recording
methods in anesthetized squirrel monkeys. 2. Nonnoxious mechanical stimulation
(vibrotactile or skin tapping) of the contralateral radial interdigital pad
was accompanied by a decrease in reflectance (at 833 nm) in sectors of
cytoarchitectonic areas 3b and 1. This intrinsic signal was in register with
regions shown by previous receptive field mapping studies to receive low-
threshold mechanoreceptor input from the radial interdigital pad. 3. A skin-
heating stimulus applied to the contralateral radial interdigital pad with a
stationary probe/thermode evoked no discernable intrinsic signal in areas 3b
and 1, but evoked a signal within a circumscribed part of area 3a. The region
of area 3a responsive to skin heating with the stationary probe/thermode was
adjacent to the areas 3b and 1 regions that developed an intrinsic signal in
response to vibrotactile stimulation of the same skin site. Skin heating with
a stationary probe / thermode also evoked intrinsic signal in regions of areas
4 and 2 neighboring the area 3b/1 regions activated by vibrotactile
stimulation of the contralateral radial interdigital pad. 4. The intrinsic
signal evoked in area 3a by a series of heating stimuli to the contralateral
radial interdigital pad (applied with a stationary probe/thermode) increased
progressively in magnitude with repeated stimulation (exhibited slow temporal
summation) and remained above prestimulus levels for a prolonged period
following termination of repetitive stimulation. 5. Brief mechanical stimuli
("taps") applied to the contralateral radial interdigital pad with a
probe/thermode maintained either at 37 degrees C or at 52 degrees C were
accompanied by the development of an intrinsic signal in both area 3a and
areas 3b/1. For the 52 degrees C stimulus, the area 3a intrinsic signal was
larger and the intrinsic signal in areas 3b/1 smaller than the corresponding
signals evoked by the 37 degrees C stimulus. 6. Spike discharge activity was
recorded from area 3a neurons during a repetitive heating stimulus applied
with a stationary probe/thermode to the contralateral radial interdigital pad.
Like the area 3a intrinsic signal elicited by repetitive heating of the same
skin site, the area 3a neuron spike discharge activity also exhibited slow
temporal summation and poststimulus response persistence. 7. The experimental
findings suggest (a) a leading role for area 3a in the anterior parietal
cortical processing of skin-heating stimuli, and (b) the presence of
inhibitory interactions between the anterior parietal responses to painful and
vibrotactile stimuli consistent with those demonstrated in recent cortical
imaging and psychophysical studies of human subjects.
Received 7 December 1995; accepted in final form 23 February 1996.
APS Manuscript Number J828-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96