Pears Andrew, Parkinson John A, Hopewell Lucy, Everitt Barry J, Roberts Angela C
Department of Anatomy, University of Cambridge, Cambridge, CB2 3DY, United Kingdom.
J Neurosci. 2003 Dec 3;23(35):11189-201. doi: 10.1523/JNEUROSCI.23-35-11189.2003.
The ventromedial prefrontal cortex (PFC) is implicated in affective and motivated behaviors. Damage to this region, which includes the orbitofrontal cortex as well as ventral sectors of medial PFC, causes profound changes in emotional and social behavior, including impairments in certain aspects of decision making. One reinforcement mechanism that may well contribute to these behaviors is conditioned reinforcement, whereby previously neutral stimuli in the environment, by virtue of their association with primary rewards, take on reinforcing value and come to support instrumental action. Conditioned reinforcers are powerful determinants of behavior and can maintain responding over protracted periods of time in the absence of and potentially in conflict with primary reinforcers. It has already been shown that conditioned reinforcement is dependent on the amygdala, and because the amygdala projects to both the orbitofrontal cortex and the medial PFC, the present study determined whether conditioned reinforcement was also dependent on one or the other of these prefrontal regions. Comparison of the behavioral effects of selective excitotoxic lesions of the PFC in the common marmoset revealed that orbitofrontal but not medial PFC lesions disrupted two distinct measures of conditioned reinforcement: (1) acquisition of a new response and (2) sensitivity to conditioned stimulus omission on a second-order schedule. In contrast, the orbitofrontal lesion did not affect sensitivity to primary reinforcement as measured by responding on a progressive-ratio schedule and a home cage consumption test. Together, these findings demonstrate the critical and specific involvement of the orbitofrontal cortex but not the medial PFC in conditioned reinforcement.
腹内侧前额叶皮质（PFC）与情感和动机行为有关。该区域受损，包括眶额叶皮质以及内侧PFC的腹侧部分，会导致情绪和社会行为发生深刻变化，包括决策某些方面的受损。一种很可能促成这些行为的强化机制是条件性强化，即环境中先前的中性刺激，由于它们与初级奖励的关联，具有了强化价值并开始支持工具性行动。条件性强化物是行为的有力决定因素，并且在没有初级强化物以及可能与初级强化物冲突的情况下，能够在很长一段时间内维持反应。已经表明条件性强化依赖于杏仁核，并且由于杏仁核投射到眶额叶皮质和内侧PFC两者，因此本研究确定条件性强化是否也依赖于这些前额叶区域中的一个或另一个。对普通狨猴PFC选择性兴奋性毒性损伤的行为效应进行比较发现，眶额叶皮质损伤而非内侧PFC损伤破坏了条件性强化的两种不同测量方法：（1）新反应的习得，以及（2）在二级程序上对条件刺激遗漏的敏感性。相比之下，眶额叶皮质损伤并不影响通过渐进比率程序和笼内消耗测试所测量的对初级强化的敏感性。总之，这些发现表明眶额叶皮质而非内侧PFC在条件性强化中起着关键且特定的作用。
