Visual working memory (VWM) allows humans to actively maintain a limited amount of information. Whereas previous electrophysiological studies have found that lateralized event-related potentials (ERPs) track the maintenance of information in VWM, recent imaging experiments have shown that spatially global representations can be read out using the activity across visual cortex. The goal of the present study was to determine whether both lateralized and spatially global electrophysiological signatures coexist. We first show that it is possible to simultaneously measure lateralized ERPs that track the number of items held in VWM from one visual hemfield and parieto-occipital alpha (8-12Hz) power over both hemispheres indexing spatially global VWM representations. Next, we replicated our findings and went on to show that this bilateral parieto-occipital alpha power as well as the contralaterally-biased ERP correlate of VWM carries a signal that can be used to decode the identity of the representations stored in VWM. Our findings not only unify observations across electrophysiology and imaging techniques, but also suggest that the ERPs and alpha-band oscillations index different neural mechanisms that map on to lateralized and spatially global representations, respectively.
- Visual working memory
- Event-related potentials
- EEG oscillation
- Copyright © 2015, Journal of Neurophysiology