Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (INCIA), Université de Bordeaux, Talence, France.
PLoS One. 2012;7(4):e33302. doi: 10.1371/journal.pone.0033302. Epub 2012 Apr 4.
In order to select actions appropriate to current needs, a subject must identify relationships between actions and events. Control over the environment is determined by the degree to which action consequences can be predicted, as described by action-outcome contingencies--i.e. performing an action should affect the probability of the outcome. We evaluated in a first experiment adaptation to contingency changes in rats with neurotoxic lesions of the medial prefrontal cortex. Results indicate that this brain region is not critical to adjust instrumental responding to a negative contingency where the rats must refrain from pressing a lever, as this action prevents reward delivery. By contrast, this brain region is required to reduce responding in a non-contingent situation where the same number of rewards is freely delivered and actions do not affect the outcome any more. In a second experiment, we determined that this effect does not result from a different perception of temporal relationships between actions and outcomes since lesioned rats adapted normally to gradually increasing delays in reward delivery. These data indicate that the medial prefrontal cortex is not directly involved in evaluating the correlation between action--and reward--rates or in the perception of reward delays. The deficit in lesioned rats appears to consist of an abnormal response to the balance between contingent and non-contingent rewards. By highlighting the role of prefrontal regions in adapting to the causal status of actions, these data contribute to our understanding of the neural basis of choice tasks.
为了选择适合当前需求的行动，主体必须识别行动和事件之间的关系。对环境的控制取决于行动后果可预测的程度，如行动-结果关联所描述的那样——即执行一个行动应该影响结果的概率。我们在第一个实验中评估了内侧前额叶皮质神经毒性损伤大鼠对关联变化的适应能力。结果表明，该脑区对于调整工具性反应并不关键，因为在这种情况下，大鼠必须避免按压杠杆，因为这种行为会阻止奖励的传递。相比之下，当相同数量的奖励被自由传递，并且行动不再影响结果时，该脑区需要减少反应。在第二个实验中，我们确定这种效果不是由于对行动和结果之间的时间关系的不同感知所致，因为损伤大鼠正常适应了奖励传递逐渐延迟的情况。这些数据表明，内侧前额叶皮质并不直接参与评估行动和奖励率之间的相关性，也不参与感知奖励延迟。损伤大鼠的缺陷似乎在于对关联和非关联奖励之间的平衡的异常反应。通过强调前额叶区域在适应行动因果状态中的作用，这些数据有助于我们理解选择任务的神经基础。
