Movement-related activity dominates cortex during sensory-guided decision making

Animal movements and internal state transitions generate an internal backdrop of activity that is dynamically modulated. During behavior, this internal backdrop interacts with signals arising from incoming sensory stimuli and may have a substantial impact on task-related computations, like those underlying decision-making. To understand the joint effects of internal backdrop and task-imposed variables, we measured neural activity across the entire dorsal cortex of task-performing mice. We characterized internal backdrop using multiple measures of self-generated parameters, e.g., pupil diameter, whisking and body motion. Surprisingly, internal backdrop dominated neural activity across the entire cortex, dwarfing task-related variables and even sensory stimuli. Single neurons in frontal cortex were likewise dominated by internal backdrop. A linear model allowed us to account for multiple dimensions of internal backdrop and uncover hidden signatures of task-related activity. The internal backdrop therefore captures a fundamental dimension of complex behavior that must be accounted for when studying decision-making.