The Journal of Cognitive Neuroscience, Vol 9, 743-757, Copyright © 1997 by The MIT Press
Effects of Memory Load and Distraction on Performance and Event-Related Slow Potentials in a Visuospatial Working Memory Task
Gina M. Geffen, Margaret J. Wright, Heather J. Green, Nicole A. Gillespie, David C. Smyth, David M. Evans and and Laurence B. Geffen
Brain electrical activity related to working memory was recorded at 15
scalp electrodes during a visuospatial delayed response task. Participants
(N = 18) touched the remembered position of a target on
a computer screen after either a 1 or 8 sec delay. These memory trials were
compared to sensory trials in which the target remained present throughout
the delay and response periods. Distractor stimuli identical to the target
were briefly presented during the delay on 30% of trials. Responses were
less accurate in memory than sensory trials, especially after the long
delay. During the delay slow potentials developed that were significantly
more negative in memory than sensory trials. The difference between memory
and sensory trials was greater at anterior than posterior electrodes. On
trials with distractors, the slow potentials generated by memory trials
showed further enhancement of negativity, whereas there were minimal
effects on accuracy of performance. The results provide evidence that
engagement of visuospatial working memory generates slow wave negativity
with a timing and distribution consistent with frontal activation. Enhanced
brain activity associated with working memory is required to maintain
performance in the presence of distraction.
