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H. Supèr, H. Spekreijse, V. A. F. Lamme; Contextual modulation in primary visual cortex as a neuronal substrate for working memory. Journal of Vision 2001;1(3):345. doi: 10.1167/1.3.345.
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© ARVO (1962-2015); The Authors (2016-present)
The visual scene is perceived as a composition of objects from which we select those that are meaningful to us. Sometimes this information needs to be maintained for a short period of time since in the constant and rapidly changing visual world a stimulus may have disappeared whereas a behavioral response to the stimulus still has to be made. During this memory period, neurons in the higher visual areas increase their firing rate to the stimulus.
In the primary visual cortex, neurons indicate whether a possible target is within their receptive fields by a late enhanced activity. This activity —contextual modulation- originates partly from feedback projections from the extra-striate cortical areas. Thus, contextual modulation in the primary visual cortex combines retinal information with activity already processed in higher visual areas.
We recorded from neurons in the primary visual cortex of macaque monkeys engaged in a delayed-response figure-ground discrimination task where the animals had to remember the location of a briefly presented figure. The results demonstrate that contextual modulation is maintained, even when the stimulus is not present, until a behavioral response is made. The strength of this modulation is weakened in case the stimulus has become irrelevant or when the stimulus position has been misjudged i.e. forgotten.
In conclusion, contextual modulation in the primary visual cortex may serve as a neural substrate for working memory.
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