Cortical State Fluctuations during Sensory Decision Making

In many behavioral tasks, cortex enters a desynchronized state where low-frequency fluctuations in population activity are suppressed. The precise behavioral correlates of desynchronization and its global organization are unclear. One hypothesis holds that desynchronization enhances stimulus coding in the relevant sensory cortex. Another hypothesis holds that desynchronization reflects global arousal, such as task engagement. Here, we trained mice on tasks where task engagement could be distinguished from sensory accuracy. Using widefield calcium imaging, we found that performance-related desynchronization was global and correlated better with engagement than with accuracy. Consistent with this link between desynchronization and engagement, rewards had a long-lasting desynchronizing effect. To determine whether engagement-related state changes depended on the relevant sensory modality, we trained mice on visual and auditory tasks and found that in both cases desynchronization was global, including regions such as somatomotor cortex. We conclude that variations in low-frequency fluctuations are predominately global and related to task engagement. •Cortical 3- to 6-Hz fluctuations are more correlated with engagement than performance•3- to 6-Hz oscillations are global and do not depend on the sensory modality of the task•Reduced slow oscillations may enable rapid, coordinated responses to sensory stimuli Jacobs et al. test the hypothesis that slow (3–6 Hz) cortical oscillations impair performance during sensory-guided decision-making tasks. They find that slow oscillations are more related to engagement than performance: mice are less likely to respond at all during increased slow oscillations, but no more likely to give an incorrect response.