Distributed networks for choice , action , 1 and engagement across the mouse brain 2

Vision, choice, action, and behavioral engagement arise from the activity of neurons 7 that may be distributed across brain regions. Here we delineate four distinct and 8 distributed networks of neurons underlying these processes. We used Neuropixels 9 probes to record from ~30,000 neurons in 42 brain regions in mice performing a visual 10 discrimination task. Neurons in nearly all regions responded non-specifically when the 11 mouse initiated an action. By contrast, neurons encoding visual stimuli and upcoming 12 choices occupied restricted regions in neocortex, basal ganglia, and midbrain. Choice 13 signals were rare and emerged simultaneously across regions. Midbrain neurons were 14 activated before contralateral choices and suppressed before ipsilateral choices, 15 whereas forebrain neurons could prefer either side. Brain-wide pre-stimulus activity 16 predicted engagement in individual trials and in the overall task, with enhanced 17 subcortical but suppressed neocortical activity during engagement. These results 18 reveal organizing principles for the distribution of neurons encoding behaviorally 19 relevant variables across the brain. 20