Abstract
Correlations between neurons can profoundly impact the information encoding capacity of a neural population. We studied how maintenance of visuospatial information affects correlated activity in visual areas by recording the activity of neurons in visual area MT of rhesus macaques during a spatial working memory task. Correlations between MT neurons depended upon the spatial overlap between neurons’ receptive fields. These correlations were influenced by the content of working memory, but the effect of a top-down memory signal differed in the presence or absence of bottom-up visual input. Neurons representing the same area of space showed increased correlations when remembering a location in their receptive fields in the absence of visual input, but decreased correlations in the presence of a visual stimulus. This set of results reveals the correlating nature of top-down signals influencing visual areas and uncovers how such a correlating signal, in interaction with bottom-up information, could enhance sensory representations.
Highlights
Correlations between neurons can profoundly impact the information encoding capacity of a neural population
Our recent work[14, 15] has shown that during spatial working memory (WM), extrastriate visual areas receive a top–down WM signal from the prefrontal cortex (PFC) and undergo subthreshold modulations based on the content of WM
In order to better understand the influence of top–down signals on the representation of information within sensory areas we studied how a top–down spatial signal modulates the correlated activity of pairs of neurons within extrastriate areas, and how these modulations depend on the similarity between the spatial and feature selectivity of the two neurons and the locus of spatial WM
Summary
Correlations between neurons can profoundly impact the information encoding capacity of a neural population. Neurons representing the same area of space showed increased correlations when remembering a location in their receptive fields in the absence of visual input, but decreased correlations in the presence of a visual stimulus This set of results reveals the correlating nature of top-down signals influencing visual areas and uncovers how such a correlating signal, in interaction with bottom-up information, could enhance sensory representations. To test whether the maintenance of spatial information alters the correlated variability of these neurons, we recorded their activity during the memory guided saccade (MGS) task, in the presence or absence of a visual stimulus during the memory period This systematic investigation revealed that an isolated spatial signal increases correlations between neurons with similar RFs; in the presence of a visual probe the top–down spatial signal instead causes a decorrelation of their responses, consistent with the results of attention studies. Based on the experimental data, we present a descriptive network model to elucidate how the top–down and bottom–up signals interact to generate the observed patterns of correlated variability among extrastriate cortical neurons
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