Unifying model for three forms of contextual modulation including feedback input from higher visual areas

Abstract

AbstractNeural responses to a localized visual stimulus are modulated by the content of its surrounding. This phenomenon manifests in several forms of contextual modulation, including three interrelated properties of the visual cortex: surround suppression, inverse response and surround facilitation. We devise a unified biologically realistic circuit model accounting for all these phenomena and show that i) surround suppression in L2/3 is only partially due to the recruitment of lateral inhibition; ii) long-range feedback projections are necessary for inverse response and iii) the width of the response profile in the feedback layer determines inverse size tuning. The model predicts the modulations induced by silencing somatostatin-expressing cells or higher visual areas or changing the stimulus contrast. These predictions are consistent with the experimental observations when available and can be tested in existing setups otherwise. We then show the robustness of the identified mechanisms in a model with three interneuron subclasses, built to fit the classical responses and able to predict inverse size-tuning curves.HighlightsOne model explains three different types of contextual modulation: (classical) surround suppression, (inverse) response to ‘holes’ in full field drifting gratings and cross orientation surround facilitation.Feedback, feedforward and lateral inhibitory inputs contribute to classical surround suppression in L2/3 of mouse V1 in different amounts.Observed responses to ‘holes’ in full field drifting gratings require long-range feedback projections.Surround modulation to the response to ‘holes’ in full field drifting gratings requires an increase in the characteristic length scale of the spatial pattern of activity in higher visual areas.The mechanisms uncovered by an analytically tractable model are also at work in a cell-type specific model that predicts response to a ‘hole’ stimulus.