An event-related brain potential correlate of visual short-term memory

EVENT-RELATED potentials (ERPs) were recorded as 12 subjects performed a de layed matching to sample task. We presented two bilateral abstract shapes a nd cued spatially which had to be memorized for a subsequent matching task: left, right or both. During memorization a posterior slow negative ERP wav e developed over the hemisphere contralateral to the memorized shape. This effect was similar in high and low memory load trials while the memory figu re were visible (for 1000 ms). As the figures disappeared (for 1500 ms), th e effect persisted only in the low memory load conditions. We suggest that the contralateral negativity reflects a visual short-term memory process an d that capacity limitation in the high memory load condition causes this pr ocess to collapse. NeuroReport 10:2001-2005 (C) 1999 Lippincott Williams & Wilkins.