Neural dynamics of covert habit activation and control in humans

The neuroscience of habits in humans presumes a winner-takes-all contest between two systems: stimulus-response and goal-directed. But lacking strong causal manipulations for inducing habits in humans, researchers have struggled to understand the brain mechanisms supporting the development of stimulus-response associations over time and their interaction with goal-directed processes. To address this, we conducted a preregistered 14-day within-subject electroencephalography (EEG) study and used tight temporal controls to isolate the functioning of each system. We found both causal and correlational evidence that the lateralized readiness potential (LRP) can serve as a covert neural signature for habits, detectable on trials where inappropriate habits are overcome and behavior is classed as goal-directed. We found evidence that stronger habits required more frontal midline theta (FM{theta}) power to successfully inhibit them, supporting the view that the goal-directed system competes with stimulus-response representations. These data showcase the hidden role of multiple brain systems in habit expression and provide a new window into the formation and override of habits.