Neuroscientists Uncover How the Brain Develops and Maintains Habits

Recent research from neuroscientists at the Sainsbury Wellcome Centre (SWC) has shed new light on how our brains form habits through a dual-system learning process. For the first time, scientists have identified a second learning mechanism that operates alongside the well-known reward-based system. This discovery enhances our understanding of habitual behaviors and opens new avenues for addressing conditions like addiction and compulsive disorders.

Published in Nature, the study utilized mice models to explore neural mechanisms involved in habit formation. The researchers revealed a dopamine-based action prediction error (APE) signal that updates the frequency of actions, functioning in parallel with the traditional reward prediction error (RPE) signal responsible for evaluating outcomes.

Dr. Marcus Stephenson-Jones, lead author, explained that once an action becomes preferred through value-based learning, the brain can bypass complex decision-making by relying on the default, habitual system driven by APE signals. This simplified storage system allows for multitasking; for example, once fluent in driving, individuals can chat while on the road because habitual behaviors are managed automatically by this second system.

Further investigation focused on the neural pathways involved, particularly in the tail of the striatum. Using fluorescent imaging and genetic techniques, the team demonstrated that movement-related dopamine signals in this area are not linked to reward, but rather to movement readiness and execution. Lesion experiments confirmed that impairing this region hampers habitual performance, indicating its critical role in storing habitual actions.

These findings have significant implications for understanding why habits are difficult to break. By targeting this second learning system, new therapeutic strategies could be developed to modify or replace harmful habits, such as those seen in addiction. Additionally, insights into dopamine neuron functions may also inform Parkinson’s disease research, providing explanations for the movement difficulties experienced by patients, which may result from the death of movement-related dopamine neurons.

The research team is currently exploring how these two systems—reward-based and habitual—interact during learning and behavior modification, with the aim of developing more effective interventions for behavioral disorders.