CAUSAL RELEVANCE OF AREAS OF THE DORSAL MOUSE CORTEX IN SENSORY-SPECIFIC REPRESENTATION FORMATION: OPTOGENETIC SCANNING STUDY

Multisensory decision-making is hypothesized to rely on cortical substrates combining distinct properties of specific modalities into unified sensory representations. Such representations are thought to emerge not in specialized integration areas, but rather through feedforward and lateral connectivity between sensory and association cortices, enabling the distinction of statistical features (e.g., spatiotemporal signal properties) unique to each modality. Growing evidence challenges the notion of strict functional segregation between sensory cortices. For example, primary visual cortex (V1) encodes multisensory, task-related and motor information in addition to visual signals, suggesting less functional specialization than previously assumed. However, the causal necessity of this multisensory activity for perception remains unclear, raising the critical question: which cortical areas are causally required for forming both unisensory and multisensory representations driving behavior? We trained 5 VGAT-ChR2⁺ mice to detect changes in continuously presented auditory and visual stimuli, achieving comparable stimulus sensitivity across modalities. We then optogenetically inhibited selected dorsal cortical targets during change detection. Inhibition of V1 produced the strongest visual performance reduction (p<0.01), followed by significant inhibition of rostrolateral (RL), anterolateral (AL), and lateromedial (LM) higher-order visual areas (HVAs; p<0.05). Effects were most pronounced for near-threshold compared to high-saliency changes. Inhibiting anterior cingulate cortex (ACC) and anteromedial (A/AM) HVAs induced nonspecific motor disinhibition (p<0.05). Auditory performance remained unaffected by any inhibition. Our results demonstrate an extended visual network beyond V1 that is causally driving visual change detection. Despite multisensory correlates previously observed in these regions, they selectively support visual perception while leaving auditory detection unaffected by inhibition.