The Journal of Neuroscience, September 1, 2001, 21(17):6978-6990
Information Conveyed by Onset Transients in Responses of Striate
Cortical Neurons
James R.
Müller1,
Andrew B.
Metha1,
John
Krauskopf2, and
Peter
Lennie1
1 Center for Visual Science and Department of Brain and
Cognitive Sciences, University of Rochester, Rochester, New York 14627, and 2 Center for Neural Science, New York University, New
York, New York 10003
Normal eye movements ensure that the visual world is seen
episodically, as a series of often stationary images. In this paper we
characterize the responses of neurons in striate cortex to stationary
grating patterns presented with abrupt onset. These responses are
distinctive. In most neurons the onset of a grating gives rise to a
transient discharge that decays with a time constant of 100 msec or
less. The early stages of response have higher contrast gain and higher
response gain than later stages. Moreover, the variability of discharge
during the onset transient is disproportionately low. These factors
together make the onset transient an information-rich component of
response, such that the detectability and discriminability of
stationary gratings grows rapidly to an early peak, within 150 msec of
the onset of the response in most neurons. The orientation selectivity
of neurons estimated from the first 150 msec of discharge to a
stationary grating is indistinguishable from the orientation selectivity estimated from longer segments of discharge to moving gratings. Moving gratings are ultimately more detectable than stationary ones, because responses to the former are continuously renewed. The principal characteristics of the response of a neuron to a
stationary grating
the initial high discharge rate, which decays
rapidly, and the change of contrast gain with time
are well captured
by a model in which each excitatory synaptic event leads to an
immediate reduction in synaptic gain, from which recovery is slow.
Key words:
visual cortex; striate cortex; detectability
(d'); discriminability; variability; reliability; refractoriness; mean-to-variance ratio; contrast gain; gain control; orientation selectivity; synaptic depression
Copyright © 2001 Society for Neuroscience 0270-6474/01/21176978-13$05.00/0