The Journal of Neuroscience, October 15, 2001, 21(20):8210-8221
Consistency of Encoding in Monkey Visual Cortex
Matthew C.
Wiener,
Mike W.
Oram,
Zheng
Liu, and
Barry J.
Richmond
Laboratory of Neuropsychology, National Institute of Mental Health,
National Institutes of Health, Bethesda, Maryland 20892-4415
Are different kinds of stimuli (for example, different classes of
geometric images or naturalistic images) encoded differently by visual
cortex, or are the principles of encoding the same for all stimuli? We
examine two response properties: (1) the range of spike counts that can
be elicited from a neuron in epochs representative of short periods of
fixation (up to 400 msec), and (2) the relation between mean and
variance of spike counts elicited by different stimuli, that together
characterize the information processing capabilities of a neuron
using the spike count code. In monkey primary visual cortex (V1)
complex cells, we examine responses elicited by static stimuli of four
kinds (photographic images, bars, gratings, and Walsh patterns); in
area TE of inferior temporal cortex, we examine responses
elicited by static stimuli in the sample, nonmatch, and match phases of
a delayed match-to-sample task. In each area, the ranges of mean spike
counts and the relation between mean and variance of spike counts
elicited are sufficiently similar across experimental conditions that
information transmission is unaffected by the differences across
stimulus set or behavioral conditions [although in 10 of 27 (37%) of
the V1 neurons there are statistically significant but small
differences, the median difference in transmitted information for these
neurons was 0.9%]. Encoding therefore appears to be consistent across
experimental conditions for neurons in both V1 and TE, and downstream
neurons could decode all incoming signals using a single set of rules.
Key words:
coding; visual; cortex; V1; TE; inferior temporal cortex; monkey; natural images; mean-variance relation
Copyright © 2001 Society for Neuroscience 0270-6474/01/21208210-12$05.00/0
Previous Article | Next Article
