Department of Psychology and Center for Memory and Brain, Boston University, Boston, MA 02215, USA.
Cereb Cortex. 2009 Nov;19(11):2561-71. doi: 10.1093/cercor/bhp006. Epub 2009 Feb 18.
Most functional magnetic resonance imaging (fMRI) studies examining working memory (WM) load have focused on the prefrontal cortex (PFC) and have demonstrated increased prefrontal activity with increased load. Here we examined WM load effects in the medial temporal lobe (MTL) using an fMRI Sternberg task with novel complex visual scenes. Trials consisted of 3 sequential events: 1) sample presentation (encoding), 2) delay period (maintenance), and 3) probe period (retrieval). During sample encoding, subjects saw either 2 or 4 pictures consecutively. During retrieval, subjects indicated whether the probe picture matched one of the sample pictures. Results revealed that activity in the left anterior hippocampal formation, bilateral retrosplenial area, and left amygdala was greater at retrieval for trials with larger memory load, whereas activity in the PFC was greater at encoding for trials with larger memory load. There was no load effect during the delay. When encoding, maintenance, and retrieval periods were compared with fixation, activity was present in the hippocampal body/tail and fusiform gyrus bilaterally during encoding and retrieval, but not maintenance. Bilateral dorsolateral prefrontal activity was present during maintenance, but not during encoding or retrieval. The results support models of WM predicting that activity in the MTL should be modulated by WM load.
大多数研究工作记忆（WM）负荷的功能磁共振成像（fMRI）研究都集中在前额叶皮层（PFC），并证明随着负荷的增加，前额叶活动增加。在这里，我们使用 fMRI Sternberg 任务和新颖的复杂视觉场景检查了内侧颞叶（MTL）中的 WM 负荷效应。试验由 3 个连续事件组成：1）样本呈现（编码），2）延迟期（维持）和 3）探针期（检索）。在样本编码期间，受试者连续看到 2 或 4 张图片。在检索期间，受试者表示探针图片是否与样本图片之一匹配。结果表明，在检索时，左前海马结构、双侧后扣带回区域和左杏仁核的活动在记忆负荷较大的情况下更大，而在记忆负荷较大的情况下，PFC 的活动在编码时更大。在延迟期间没有负荷效应。当将编码、维持和检索期与注视期进行比较时，在编码和检索期间双侧海马体/尾部和梭状回都存在活动，但在维持期间没有。双侧背外侧前额叶在维持期间活动，但在编码或检索期间不活动。这些结果支持 WM 模型的预测，即 MTL 的活动应该受到 WM 负荷的调节。
