A MULTIMODAL APPROACH FOR SPATIALLY SELECTIVE CORTICAL INACTIVATION IN HEAD-FIXED MICE

Perceptual decision-making emerges from interactions between neurons across a distributed cortical network. Mechanistic investigation of this process therefore requires experimental approaches that enable both large-scale recording and spatially precise manipulation of cortical activity. Here we introduce a multimodal protocol that combines wide-field calcium imaging and spatially selective optogenetics to functionally map and manipulate user-defined cortical regions in head-fixed mice during a perceptual decision-making task.
Using wide-field calcium imaging through a transparent polydimethylsiloxane (PDMS) window, we first map neural activity across the dorsal cortex in head-fixed, behaving mice to identify regions responsive to sensory stimulation. Based on these functional maps, we generate binary illumination masks corresponding to arbitrarily-shaped cortical subregions to be targeted for optogenetic activation or inactivation. Masks are projected onto the cortical surface via a laser-based projection system, enabling confined light delivery to selected areas while minimizing off-target illumination. Light wavelength is adapted to the employed opsin, providing flexibility across experimental configurations. This method provides high spatial specificity for targeting functionally defined cortical areas and can be readily combined with complementary techniques such as electrophysiological recordings.
Preliminary results demonstrate that focal, functionally targeted optogenetic inactivation of small subregions within primary visual cortex, achieved with an effective spatial resolution of ~300 μm, selectively modulates visually evoked behavioral responses. Overall, this framework offers a versatile and precise tool to causally investigate the contributions of distributed cortical populations to perceptual decision-making.