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Moshe Gur, Igor Kagan, Max D. Snodderly; Lack of short-term adaptation in V1 cells of the alert monkey. Journal of Vision 2004;4(8):223. doi: 10.1167/4.8.223.
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© ARVO (1962-2015); The Authors (2016-present)
Although prolonged adaptation is a very useful experimental tool, its relevancy to normal vision, which consists of series of short fixational epochs, is not clear. Directly related to perception is short-term pattern adaptation where a stimulus is quickly followed by an identical one. Recently, strong adaptation effects have been demonstrated in both V1 single cell recordings and fMRI. V1 single cells adaptation has been proposed as the basis of fMRI adaptation and as improving the discriminability of signals arising from successively viewed images of similar structures. We have previously shown, in alert monkeys, that responses of V1 cells to repeated stimuli is much less variable than that found in the anesthetized preparation. Here we report on the degree of adaptation in V1 cells to repeated, identical brief stimuli. Recordings were made from single cells in area V1 of alert monkeys performing a fixation task. The cells' spatial organization was studied with drifting increment and decrement bars while compensating for fixational drifts. Cells were stimulated with optimally oriented flashing or sweeping bars during a 5 sec fixation trial. No cells showed the strong clear adaptation effects found in the anesthetized preparation and the great majority did not adapt at all. When non-optimal stimuli were used, response variability increased. We conclude that fMRI adaptation does not originate in V1 and that, in repeated viewing, discriminability between similar but not identical features is predicated on different responses of neuronal populations finely tuned to different features. That responses to optimal stimuli do not adapt and are much less variable than responses to non-optimal ones, is consistent with this discrimination scheme.
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