ABC colloquium - Laura Busse, Ludwig-Maximilians University Munich
Contextual influences on information processing in the mouse early visual system. A causal test of V1’s role in visual awareness.
The primary visual cortex (V1) is the main source of visual input to downstream cortical areas; it is a long-standing question, however, whether V1 activity is critical for conscious visual perception. Previous studies have exploited visual illusions that render stimuli invisible, such as binocular rivalry or backward masking, but have provided conflicting results.
Moreover, in these paradigms, the role of a candidate area in visual perception was often based on correlations between its neural activity and subjective reports of visibility. Mere correlations, however, may reflect spurious relationships, and ultimate answers about an area’s contribution to perception will require methods demonstrating causality.
Here we provide a causal test of V1’s role in perception by porting the backward masking paradigm to the mouse model, where we combine behavior, electrophysiology, and optogenetic manipulations of neural activity. We first demonstrate that the behavioral signatures of visual backward masking known from humans and non-human primates are also present in the mouse. We then characterize a prolonged response component of V1 neurons, which is indeed correlated with the mouse’s report of visibility. Despite this correlation, we find that this prolonged V1 response component is not causally linked to perception, because temporally precise suppression of it leaves behavioral performance fully intact.
We conclude that V1 functions as an input source of visual information to later areas, but is not part of the circuitry critical for visual perception.
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