Frontal-parietal activation differences observed before the execution of remembered saccades: an event-related potentials study

Healthy subjects performed saccadic eye movements in one memory (MEM) and t wo (delay tasks delay, DEL and modified delay, M-DEL) while we recorded sca lp event-related potentials (ERPs) from 25 electrode sites. In the MEM task the subjects were instructed to retain in memory the location of a visual target for a delay of 1-6 s and then perform a remembered saccade at the go signal. In the DEL task, the target remained on until movement completion and in the M-DEL task the target, that was visible during the delay period, disappeared synchronously with the go signal. A reduction in response late ncy and an increase in the percentage of dysmetric movements were observed fur the MEM task compared to the two delay tasks. An increased ERP activity at the central-frontal electrode sites compared to the parietal sites was significant only for the MEM task early on during the delay period (500-100 0 ms). During the period preceding the onset of the saccade, a parietal inc rease of activity was observed for all tasks. Furthermore the activity was smaller for the frontal compared to the parietal areas only for the memory task thus indicating a near reversal of the previous pattern of activity ob served during the early delay period. This specific activation pattern of f rontal and parietal areas, observed for the MEM task only, requires further investigation focusing on the temporal pattern of activation of large brai n areas involved in working memory processing. (C) 2001 Elsevier Science B. V. All rights reserved.