Figure 1.
Exposure to chronic stress does not influence the acquisition of instrumental tasks and activates the associative fronto-striatal network. (a) Mean score of the stress perceived questionnaire (control vs stress t22=3.429, P=0.002; stress vs stress recovered t11=3.663, P=0.004). (b) Response rate during the acquisition of the task, for the valued rewards ((b1) chocolate, (b2) tomato) in both the high (chocolate: control t11=2.568, P=0.026; stress t11=3.806, P=0.003; stress recovered t11=2.615, P=0.024; tomato: control t11=3.144, P=0.009; stress t11=2.556, P=0.027; stress recovered t11=2.828, P=0.016) and the low probability options (chocolate: control t11=1.321, P=0.213; stress t11=2.152, P=0.054; stress recovered t11=3.120, P=0.010; tomato: control t11=2.677, P=0.022; stress t11=2.335, P=0.039; stress recovered t11=2.187, P=0.051). No significant differences were found between groups. (c1), Pattern of activation when deciding between high- vs low-value choices during the learning phase of the task (that is, contrast between the last and first block of the first session). The activation in the medial prefrontal cortex (left medial superior gyrus; x=−10, y=44, z=32; Z score=2.81; P<0.002, uncorrected) demonstrates the engagement of this brain region during the acquisition of the decision task. No other brain region showed effects at this significance in this contrast. (c2), Pattern of brain activation in controls throughout the learning phase of the task. There is activation of components of the associative network, namely the medial prefrontal cortex (anterior cingulate: x=0, y=10, z=42; Z score=4.13; P<0.05, corrected for small volume for family wise error (FWE)) and the caudate nucleus (left: x=−12, y=6, z=10; Z score=4.49; P<0.05, corrected for small volume for FWE and right x=18, y=10, z=18; Z score=3.67; P<0.05, corrected for small volume for FWE).