De Pisapia Nicola, Slomski Jessica A, Braver Todd S
Department of Psychology, Washington University, Saint Louis, MO 63139, USA.
Cereb Cortex. 2007 May;17(5):993-1006. doi: 10.1093/cercor/bhl010. Epub 2006 Jun 12.
Control processes are thought to play an important role in working memory (WM), by enabling the coordination, transformation, and integration of stored information. Yet little is known about the neural mechanisms that subserve such control processes. This study examined whether integration operations within WM involve the activation of distinct neural mechanisms within lateral prefrontal cortex (PFC). Event-related functional magnetic resonance imaging was used to monitor brain activity while participants performed a mental arithmetic task. In the integration (IN) condition, a WM preload item had to be mentally inserted into the last step of the math problem. This contrasted with the segregation (SG) condition, which also required maintenance of the WM preload while performing mental arithmetic but had no integration requirement. Two additional control conditions involved either ignoring the preload (math only condition) or ignoring the math problem (recall only condition). Left anterior PFC (Brodmann's Area [BA] 46/10) was selectively engaged by integration demands, with activation increasing prior to, as well as during the integration period. A homologous right anterior PFC region showed selectively increased activity in the SG condition during the period in which the math problem and preload digit were reported. Left middorsolateral PFC regions (BA 9/46) showed increased, but equivalent, activity in both the SG and IN conditions relative to both control conditions. These results provide support for the selective role of lateral PFC in cognitive control over WM and suggest more specific hypotheses regarding dissociable PFC mechanisms involved during the integration and segregation of stored WM items.
控制过程被认为在工作记忆（WM）中发挥着重要作用，它能够使存储信息进行协调、转换和整合。然而，对于支持此类控制过程的神经机制却知之甚少。本研究考察了工作记忆中的整合操作是否涉及外侧前额叶皮质（PFC）内不同神经机制的激活。在参与者执行心算任务时，采用事件相关功能磁共振成像来监测大脑活动。在整合（IN）条件下，一个工作记忆预载项目必须在脑海中插入到数学问题的最后一步。这与分离（SG）条件形成对比，分离条件在执行心算时也需要维持工作记忆预载，但没有整合要求。另外两个控制条件分别是忽略预载（仅数学条件）或忽略数学问题（仅回忆条件）。整合需求选择性地激活了左前PFC（布罗德曼区[BA]46/10），在整合期之前以及整合期内激活都有所增加。在报告数学问题和预载数字的期间，同源的右前PFC区域在SG条件下显示出选择性增加的活动。相对于两个控制条件，左中背外侧PFC区域（BA 9/46）在SG和IN条件下均显示出增加但相当的活动。这些结果为外侧PFC在对工作记忆的认知控制中的选择性作用提供了支持，并提出了关于在存储的工作记忆项目整合和分离过程中涉及的可分离PFC机制的更具体假设。
