The role of pre-stimulus alpha rhythms in non-retinotopic feature integration

What is the link between spontaneous neuronal oscillations (i.e., non-evoked activity) and perception? Often, the phase or power of alpha activity is proposed to modulate perception. The majority of work has focused on the unecological presentation of single stimuli at threshold. Here, we investigated the relation between pre-stimulus electroencephalography (EEG) rhythms and non-retinotopic integration of visual features in the sequential metacontrast paradigm (SQM), where information needs to be integrated across space and time. In the SQM, participants discriminate the offset of a central line followed by a stream of flanking lines. Metacontrast masking makes the central line invisible, but its offset can be perceived in the motion stream. When a second line in the stream has an offset in the opposite direction, the two offsets integrate. Using linear discriminant analysis, we isolated electrodes carrying information about the reported offset in the stream. Pre-stimulus alpha activity at these electrodes was predictive of the reported percept: increases in alpha power led to more frequent reports of the first offset, decreases in alpha power to more frequent reports of the second. These results indicate that spontaneous alpha rhythms may modulate the relative weighting of visual features embedded in a continuous stream.