Differential activation of the human orbital, mid-ventrolateral, and mid-dorsolateral prefrontal cortex during the processing of visual stimuli

There is considerable uncertainty about the precise functional contribution of the different parts of the prefrontal cortex to mnemonic processing. Changes in regional cerebral blood flow were measured with positron emission tomography in normal human subjects exposed to abstract visual designs under various conditions. It was demonstrated that the processing of stimuli that deviate from expectations involves selectively the orbitofrontal cortex, namely the part of the frontal cortex that is preferentially linked with the limbic system. By contrast, when the subject is making an explicit decision on the contents of memory (e.g., judgments of relative stimulus familiarity), the mid-ventrolateral prefrontal cortex is involved. The mid-dorsolateral prefrontal cortex is engaged when monitoring of information within working memory is required.

目前学界对于前额叶皮层（prefrontal cortex）不同亚区在记忆加工中的精准功能贡献，仍存在较大不确定性。本研究在多种实验条件下，向健康人类受试者呈现抽象视觉图案，并通过正电子发射断层扫描（positron emission tomography）测量其脑区局部血流量变化。研究证实，当加工违背预期的刺激时，眶额叶皮层（orbitofrontal cortex）会被选择性招募参与该过程——该脑区即与边缘系统（limbic system）存在优先神经联结的额叶皮层亚区。与之相对，当受试者对记忆内容做出外显判断（例如对刺激相对熟悉度的评定）时，腹中侧前额叶皮层（mid-ventrolateral prefrontal cortex）会参与该加工过程。而当需要对工作记忆（working memory）中的信息进行监控时，中背外侧前额叶皮层（mid-dorsolateral prefrontal cortex）则会被激活参与对应任务。