D. Kleinfeld et Kr. Delaney, DISTRIBUTED REPRESENTATION OF VIBRISSA MOVEMENT IN THE UPPER LAYERS OF SOMATOSENSORY CORTEX REVEALED WITH VOLTAGE-SENSITIVE DYES, Journal of comparative neurology, 375(1), 1996, pp. 89-108
We have identified large-scale patterns of electrical activity in cort
ical circuits that occur in response to stimulation of peripheral rece
ptors. Our focus was on primary (S1) vibrissal cortex of anesthetized
rat, and we used optical techniques in conjunction with voltage-sensit
ive dyes to measure depolarization of the upper layers of cortex. Disp
lacement of one vibrissa produced a field of activity that extends ove
r very many cortical columns in S1. There are multiple, focal maxima w
ithin this field. A global maximum is located near the center of the f
ield of activity, and, as determined electrically and histologically,
this site maps to the cortical column appropriate for the deflected vi
brissa. The amplitude of this component attains a steady-state value u
nder continuous stimulation. Additional temporal characteristics are r
evealed by the response to a single displacement; the signal was triph
asic and began with a prompt depolarization that was followed by a tra
nsient phase of inhibition and a final phase of long-lasting depolariz
ation. The somatotopy of the other, satellite maxima in the field of a
ctivity were established through the reconstruction of the fields of a
ctivity produced by individual stimulation of other vibrissae. Local m
axima for one vibrissa were seen to overlie the global maximum found f
or stimulation of nearest- and next-nearest-neighbor vibrissae. In con
trast to the amplitude of the global maxima, the amplitude associated
with the local maxima was not maintained with either continuous or inf
requent but repetitive stimulation. Finally, the field of activity ind
uced by alternate deflection of two neighboring vibrissae was suppress
ed in amplitude in comparison to the summed amplitudes of the signals
elicited by deflection of each vibrissa alone. We suggest that these p
atterns of activity are a manifestation of the dynamic interaction amo
ng neighboring cortical columns. (C) 1996 Wiley-Liss, Inc.