Visual evidence accumulation guides decision-making in unrestrained mice

A major challenge to studying the neural circuits underlying perceptual decision making has been the limited availability of tools for manipulation of neural activity. In recent years, rodents have emerged as a desirable model for overcoming the technical hurdle. However, mice, which offer abundant genetic tools for circuit manipulation, are underrepresented in perceptual evidence accumulation studies. Here we describe the behavior of mice performing a visual evidence accumulation task similar to one previously used in rats and humans. We found that although mice were capable of achieving similar accuracy levels as rats, differences in accumulation strategy were apparent. To test the engagement of cortex in the visual evidence accumulation task, we optogenetically inhibited activity in the anteromedial (AM) visual area using JAWS. Importantly, light activation biased choices in both injected and uninjected animals. Fortunately, by varying the stimulus-response contingency while holding constant the stimulated hemisphere, we surmounted this obstacle and demonstrated a role for AM in contralateral choices. Taken together, our results argue that mice accumulate visual evidence to guide decisions, an ability that is supported in part by area AM.