|Arquivo PCA - Pasta 11/2006
|Chronic stress causes corticostriatal reorganization and affects decision-making
Maladaptive responses to stress depend on the intensity and duration of stressors; chronic exposure to stressful events has been shown to predispose to several conditions raging from neuropsychiatric disorders to everyday lapses of attention. Several reports implicate chronic stress in executive function impairment. In this study, we investigated the impact that chronic stress (21 days of chronic unpredictable stress (CUS)) would have on corticostriatal circuits, which are critical for decision making. By 3-D analysis of Golgi stained neurons, we confirmed our previous results indicating that exposure to chronic stress results in dramatic reductions in the total length of apical dendrites in the pyramidal neurons in layer II/III of the prelimbic (PL) and infralimbic (IL) sub-regions of medial prefrontal cortex (mPFC). Interestingly, the impact of chronic stress on the striatum was not uniform: while we found a significant increase in the total length of dendrites in the medium spiny neurons (MSNs) of the dorsolateral striatum (DLS, or sensorimotor striatum), there was a trend to a decrease in the total length of dendrites in MSNs of the dorsomedial striatum (DMS). Taken together these data suggest that chronic stress causes opposing structural changes in associative and sensorimotor corticostriatal networks. These different circuits have been implicated in different types of actions: the PL cortex and the DMS have been implicated in goal-directed actions, which depend on the relation between the execution of the action and potential outcomes, and on the expected value of those outcomes. In contrast, the DLS has been implicated in the formation of habits, which are insensitive to changes in outcome value and changes in the contingency between action and outcome. Therefore, it is conceivable that chronic stress could play a role in decision-making driving the behavior control from actions to habits. In order to test this hypothesis, rats submitted to chronic stress were trained to press a lever for specific outcomes and subsequently tested for their action-outcome behavior. Using two different behavioral assays, we found that responses from animals submitted to chronic stress became insensitive to both outcome devaluation and contingency degradation. Taken together, our data suggests that chronic stress causes a dramatic structural reorganization of corticostriatal circuits, which results in impaired goal-directed behavior and increased predisposition for habit formation.
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|Sousa, J., Melo, I., Mesquita, A. R., Cerqueira, J., Costa, R. M., Sousa, N.
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|Dias-Ferreira, E., Sousa, J., Melo, I., Mesquita, A. R., Cerqueira, J., Costa, R. M., & Sousa, N. (2008). Chronic stress causes corticostriatal reorganization and affects decision-making. Program No. 195.5/UU54. 2008 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience. Online.
|Chronic stress / Decision-making / Striatum / Corticosteroids