Gevins A, Cutillo B
EEG Systems Laboratory and SAM Technology, San Francisco, CA 94107.
Electroencephalogr Clin Neurophysiol. 1993 Sep;87(3):128-43. doi: 10.1016/0013-4694(93)90119-g.
Working memory (WM), the ability to momentarily maintain information in an active state, is central to higher cognitive functions. The processes involved in WM operate on a sub-second timescale, and thus evoked potential measures have an appropriate temporal resolution for studying them. In the experiment reported here, evoked potential covariances (EPC) between scalp recording sites were computed for a task requiring maintenance of numeric information in WM; these EPCs were compared to those observed in a control task which had the same stimuli and responses but less of a WM requirement. EPC patterns differed between conditions prior to the stimulus, and in an interval spanning the P300 peak in the match detection trials which required response inhibition. The pattern of prestimulus EPCs was more complex and left-sided in the WM task, when memory codes were being maintained and responses contingent on those codes were being prepared. P300 peak latency was 140 msec shorter in the WM task, and the P300 EPC pattern was more anterior and left-sided. In contrast, EPC patterns did not differ during early stages of stimulus processing or during response execution. These results suggest that distinct EPC patterns associated with WM only occur during intervals in which the information in an active state is being utilized for task performance.
工作记忆（WM），即将信息暂时维持在活跃状态的能力，是更高层次认知功能的核心。工作记忆所涉及的过程在亚秒级时间尺度上运作，因此诱发电位测量对于研究这些过程具有合适的时间分辨率。在本文报道的实验中，针对一项需要在工作记忆中维持数字信息的任务，计算头皮记录部位之间的诱发电位协方差（EPC）；将这些EPC与在一项对照任务中观察到的EPC进行比较，该对照任务具有相同的刺激和反应，但对工作记忆的要求较低。在刺激之前的条件下，以及在需要反应抑制的匹配检测试验中跨越P300峰值的时间段内，EPC模式在不同条件之间存在差异。当维持记忆编码并准备基于这些编码的反应时，在工作记忆任务中，刺激前EPC的模式更复杂且偏向左侧。在工作记忆任务中，P300峰值潜伏期缩短了140毫秒，并且P300 EPC模式更靠前且偏向左侧。相比之下，在刺激处理的早期阶段或反应执行期间，EPC模式没有差异。这些结果表明，与工作记忆相关的独特EPC模式仅在将活跃状态的信息用于任务执行的时间段内出现。
