EFFECTS OF MEMORY LOAD AND DISTRACTION ON PERFORMANCE AND EVENT-RELATED SLOW POTENTIALS IN A VISUOSPATIAL WORKING-MEMORY TASK

Brain electrical activity related to working memory was recorded at 15 scalp electrodes during a visuospatial delayed response task. Partici pants (N = 18) touched the remembered position of a target on a comput er screen after either a 1 or 8 sec delay. These memory trials were co mpared to sensory trials in which the target remained present througho ut the delay and response periods. Distracter stimuli identical to the target were briefly presented during the delay on 30% of trials. Resp onses were less accurate in memory than sensory trials, especially aft er the long delay. During the delay slow potentials developed that wer e significantly more negative in memory than sensory trials. The diffe rence between memory and sensory trials was greater at anterior than p osterior electrodes. On trials with distracters, the slow potentials g enerated by memory trials showed further enhancement of negativity whe reas there were minimal effects on accuracy of performance. The result s provide evidence that engagement of visuospatial working memory gene rates slow wave negativity with a timing and distribution consistent w ith frontal activation. Enhanced brain activity associated with workin g memory is required to maintain performance in the presence of distra ction.