REFLECTION OF WORKING-MEMORY - ERP MNEMONIC EFFECTS

The study of working memory often utilizes a delayed matching to sampl e paradigm (DMS). Typically in the matching condition, the test and sa mple stimuli are identical, raising the possible confound of retinotop ic projections for the matching stimuli in contrast to the nonmatching stimuli. In the present study, 65 healthy subjects performed a modifi ed delayed matching to sample task while monitoring their ERP waveform s. The stimuli consisted of 60 different sample stimuli (S1) and 60 di fferent test stimuli (S2). Half of the S2s were complementary to the s ample stimuli (Fit) the other half of the S2s were not complementary ( Nonfit). After 52, the subjects pressed one of the buttons to indicate whether the test stimulus fits the sample stimulus. Our statistical r esults indicated that the ERPs to sample stimuli differed from the ERP s to test stimuli from 200 ms poststimulus to the end of the recording epoch. The ERPs to fitting stimuli were significantly different from those to non-fitting stimuli from 200 to 400 ms poststimulus. The ERP patterns in the present study may reflect ERP mnemonic effect for work ing memory. Our results ruled out the retinotopic confound as a potent ial mediator variable, and are in agreement with other animal or human neurophysiological studies on memory. (C) 1997 Elsevier Science Irela nd Ltd.