Abstract
Alpha-frequency band oscillations have been shown to be one of the most prominent aspects of neuronal ongoing oscillatory activity, as reflected by electroencephalography (EEG) recordings. First thought to reflect an idling state, a recent framework indicates that alpha power reflects cortical inhibition. In the present study, the role of oscillations in the upper alpha-band (12 Hz) was investigated during a change-detection test of short-term visual memory. If alpha oscillations arise from a purely inhibitory process, higher alpha power before sample stimulus presentation would be expected to correlate with poorer performance. Instead, participants with faster reaction-times showed stronger alpha power before the sample stimulus in frontal and posterior regions. Additionally, faster participants showed stronger alpha desynchronization after the stimulus in a group of right frontal and left posterior electrodes. The same pattern of electrodes showed stronger alpha with higher working-memory load, so that when more items were processed, alpha power desynchronized faster after the stimulus. During memory maintenance, alpha power was greater when more items were held in memory, likely due to a faster resynchronization. These data are consistent with the hypothesis that the level of suppression of alpha power by stimulus presentation is an important factor for successfully encoding visual stimuli. The data are also consistent with a role for alpha as actively participating in attentional processes.
Highlights
Since its first observation in 1929 by Hans Berger (Berger, 1929), many interpretations have been proposed to explain the presence of alpha oscillations (8–14 Hz) in the cortex
We know that ongoing brain activity is dominated by alpha oscillations (Linkenkaer-Hansen et al, 2004) and that alpha is deeply involved in vision and attention processes (Klimesch et al, 2008)
ALPHA WHILE PREPARING FOR THE STIMULUS Between-subject correlation coefficients were calculated between behavioral scores and the average value of 12 Hz alpha power between 500 ms and 200 ms before stimulus onset in each electrode
Summary
Since its first observation in 1929 by Hans Berger (Berger, 1929), many interpretations have been proposed to explain the presence of alpha oscillations (8–14 Hz) in the cortex. A current leading interpretation of alpha oscillations is a framework where the amplitude of alpha reflects a certain level of cortical inhibition (Ray and Cole, 1985; Pfurtscheller, 2003; Klimesch et al, 2007; Mathewson et al, 2009; Sauseng et al, 2009; Jensen and Mazaheri, 2010) This idea has emerged from experiments where participants were asked to focus their attention either on a part of visual space (Thut et al, 2006) or on a particular feature of visual stimuli (Snyder and Foxe, 2010) and studies comparing auditory and visual stimuli (Foxe et al, 1998). In working-memory tasks, alpha has been found to relate to the quantity of information to remember (Jensen et al, 2002)
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