Avoidance learning: a review of theoretical models and recent developments

This review outlines recent findings from human neuroimaging concerning the role of a highly interconnected network of brain areas including orbital and medial prefrontal cortex, amygdala, striatum and dopaminergic mid-brain in reward processing. Distinct reward-related functions can be attributed to different components of this network. Orbitofrontal cortex is involved in coding stimulus reward value and in concert with the amygdala and ventral striatum is implicated in representing predicted future reward. Such representations can be used to guide action selection for reward, a process that depends, at least in part, on orbital and medial prefrontal cortex as well as dorsal striatum.

Dopamine signaling is implicated in reinforcement learning, but the neural substrates targeted by dopamine are poorly understood. Here, we bypassed dopamine signaling itself and tested how optogenetic activation of dopamine D1- or D2-receptor-expressing striatal projection neurons influenced reinforcement learning in mice. Stimulating D1-expressing neurons induced persistent reinforcement, whereas stimulating D2-expressing neurons induced transient punishment, demonstrating that activation of these circuits is sufficient to modify the probability of performing future actions.

The present model outlines the mechanisms underlying habitual control of responding and the ways in which habits interface with goals. Habits emerge from the gradual learning of associations between responses and the features of performance contexts that have historically covaried with them (e.g., physical settings, preceding actions). Once a habit is formed, perception of contexts triggers the associated response without a mediating goal. Nonetheless, habits interface with goals. Constraining this interface, habit associations accrue slowly and do not shift appreciably with current goal states or infrequent counterhabitual responses. Given these constraints, goals can (a) direct habits by motivating repetition that leads to habit formation and by promoting exposure to cues that trigger habits, (b) be inferred from habits, and (c) interact with habits in ways that preserve the learned habit associations. Finally, the authors outline the implications of the model for habit change, especially for the self-regulation of habit cuing. PsycINFO Database Record (c) 2007 APA, all rights reserved.