Sayala Seema, Sala Joseph B, Courtney Susan M
Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
Cereb Cortex. 2006 May;16(5):609-17. doi: 10.1093/cercor/bhj007. Epub 2005 Aug 3.
Unlike tasks in which practice leads to an automatic stimulus-response association, it is thought working memory (WM) tasks continue to require cognitive control processes after repeated performance. Previous studies investigating WM task repetition are in accord with this. However, it is unclear whether changes in neural activity after repetition imply alterations in general control processes common to all WM tasks or are specific to the selection, encoding and maintenance of the relevant information. In the present study, functional magnetic resonance imaging (fMRI) was used to examine changes during sample, delay and test periods during repetition of both object and spatial delayed recognition tasks. We found decreases in fMRI activation in both spatial and object-selective areas after spatial WM task repetition, independent of behavioral performance. Few areas showed changed activity after object WM task repetition. These results indicate that spatial task repetition leads to increased efficiency of maintaining task-relevant information and improved ability to filter out task-irrelevant information. The specificity of this repetition effect to the spatial task suggests a difference exists in the nature of the representation of object and spatial information and that their maintenance in WM is likely subserved by different neural systems.
与那些通过练习可形成自动刺激-反应关联的任务不同，人们认为工作记忆（WM）任务在反复执行后仍需认知控制过程。此前研究WM任务重复的实验结果与此相符。然而，尚不清楚重复后神经活动的变化是意味着所有WM任务共有的一般控制过程发生了改变，还是特定于相关信息的选择、编码和维持。在本研究中，功能磁共振成像（fMRI）被用于检测客体和空间延迟识别任务重复过程中采样期、延迟期和测试期的变化。我们发现，空间WM任务重复后，空间和客体选择性区域的fMRI激活均降低，且与行为表现无关。客体WM任务重复后，很少有区域的活动发生改变。这些结果表明，空间任务重复可提高维持任务相关信息的效率，并增强过滤任务无关信息的能力。这种重复效应对空间任务的特异性表明，客体和空间信息表征的性质存在差异，且它们在WM中的维持可能由不同的神经系统支持。
