Transcranial direct current stimulation over right posterior parietal cortex changes prestimulus alpha oscillation in visual short-term memory task

Alpha band activity changes accompanied with the level attentional state, and recent studies suggest that suc' oscillation is associated with activities in the posterior parietal cortex. Here we show that artificially elevating parietal activity via positively-charged electric current through the skull can rapidly and effortlessly change people'prestimulus alpha power and improve subsequent performance on a visual short-term memory (VSTM) task. This modulation of alpha power and behavioral performance, however, is dependent on people's natural VSTIV capability such that only the low performers benefitted from the stimulation, whereas high performers dic not. This behavioral dichotomy is accounted by prestimulus alpha powers around the parieto-occipital regions low performers showed decreased prestimulus alpha power, suggesting improvement in attention deploymen in the current paradigm, whereas the high performers did not benefit from tDCS as they showed equally-low prestimulus alpha power before and after the stimulation. Together, these results suggest that prestimulus alpha power, especially in low performers, can be modulated by anodal stimulation and alter subsequen VSTM performance/capacity. Thus, measuring alpha before stimulus onset may be as important as measuring other VSTM-related electrophysiological components such as attentional allocation and memory capacity relate components (i.e. N2 posterior-contralateral, N2pc, or contralateral delay activity, CDA). In addition, low VST1V performers perhaps do not suffer not only from poor VSTM capacity, but also from broad attentional mechanisms and prestimulus alpha may be an useful tool in understanding the nature of individual differences in VSTM. (C) 2014 Elsevier Inc. All rights reserved.