Stress-induced modulation of instrumental behavior: from goal-directed to habitual control of action.

Actions that are directed at achieving pleasant or avoiding unpleasant states are referred to as instrumental. The acquisition of instrumental actions can be controlled by two anatomically and functionally distinct processes: a goal-directed process that is based on the prefrontal cortex and dorsomedial striatum and encodes the causal relationship between an action and the motivational value of the outcome and a dorsolateral striatum-based habit process that learns associations between actions and antecedent stimuli. Here, we review recent research showing that stress modulates the control of instrumental action in a manner that favors habitual over goal-directed action. At the neuroendocrine level, this stress-induced shift towards habit action requires the concerted action of glucocorticoids and noradrenergic arousal and is most likely accompanied by opposite functional changes in the corticostriatal circuits underlying goal-directed and habitual actions. Although generally adaptive, these changes in the control of instrumental action under stress may promote dysfunctional behaviors and the development of psychiatric disorders such as addiction.