Neural dynamics of covert habit activation and control in humans

Abstract

The neuroscience of habits in humans presumes a competition 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 electroencephalography (EEG) study with 14 days of stimulus-response training and used tight temporal controls to isolate the functioning of each system. In line with our preregistered hypothesis, we found that the lateralized readiness potential (LRP) tracked covert activation of habitual responses, detectable on trials where inappropriate habits are overcome and behavior is classed as goal-directed. In exploratory analyses, the strength of this covert habitual activation was associated with the degree of inappropriate habit expression on separate trials where response preparation time was limited. Further, exploratory analyses suggested that frontal midline theta (FM{theta}) power was selectively elevated when extensively trained habits needed to be overridden, and that this elevation scaled with individual differences in habit expression. These data provide evidence consistent with a dual systems account in which habit expression reflects competition between distinct neural subsystems and offer a new window into the formation and override of habits.