Casey B J, Forman S D, Franzen P, Berkowitz A, Braver T S, Nystrom L E, Thomas K M, Noll D C
Sackler Institute for Developmental Psychobiology, Weill Medical College of Cornell University, New York, New York 10021, USA.
Hum Brain Mapp. 2001 May;13(1):26-33. doi: 10.1002/hbm.1022.
Electrophysiological studies suggest sensitivity of the prefrontal cortex to changes in the probability of an event. The purpose of this study was to determine if subregions of the prefrontal cortex respond differentially to changes in target probabilities using functional magnetic resonance imaging (fMRI). Ten right-handed adults were scanned using a gradient-echo, echo planar imaging sequence during performance of an oddball paradigm. Subjects were instructed to respond to any letter but "X". The frequency of targets (i.e., any letter but X) varied across trials. The results showed that dorsal prefrontal regions were active during infrequent events and ventral prefrontal regions were active during frequent events. Further, we observed an inverse relation between the dorsal and ventral prefrontal regions such that when activity in dorsal prefrontal regions increased, activity in ventral prefrontal regions decreased, and vice versa. This finding may index competing cognitive processes or capacity limitations. Most importantly, these findings taken as a whole suggest that any simple theory of prefrontal cortex function must take into account the sensitivity of this region to changes in target probability.
电生理研究表明前额叶皮质对事件概率变化敏感。本研究的目的是使用功能磁共振成像（fMRI）来确定前额叶皮质的亚区域是否对目标概率变化有不同反应。10名右利手成年人在执行奇偶数范式任务期间，使用梯度回波、回波平面成像序列进行扫描。受试者被指示对除“X”以外的任何字母做出反应。目标（即除X以外的任何字母）的出现频率在各试验中有所不同。结果显示，背侧前额叶区域在罕见事件期间活跃，腹侧前额叶区域在频繁事件期间活跃。此外，我们观察到背侧和腹侧前额叶区域之间存在反比关系，即当背侧前额叶区域的活动增加时，腹侧前额叶区域的活动减少，反之亦然。这一发现可能表明存在相互竞争的认知过程或能力限制。最重要的是，这些发现总体上表明，任何关于前额叶皮质功能的简单理论都必须考虑到该区域对目标概率变化的敏感性。
