Widespread cortical α-ERD accompanying visual oddball target stimuli is frequency but non-modality specific.

Previous studies have shown that alpha event-related desynchronization (α-ERD) is associated with reaction to visual stimuli in oddball paradigm, as a reflection of attention allocation and memory updating. The present study tested the hypothesis that it reflects a modality and/or frequency specific mechanism. Electroencephalography (EEG) recordings (64 channels) were performed on 18 healthy subjects during visual, auditory, somatosensory, and pain oddball paradigms. Low- and high-frequency α-rhythm were analyzed on individual basis, and their sources were estimated by low resolution brain electromagnetic tomography (LORETA). α-ERD, served as an index of cortical activation, was computed on the cortical voxel level and compared across the conditions (target vs. non-target), α sub-bands (lower vs. higher frequency), and modalities (visual, auditory, somatosensory, and pain). The results showed that visual α-ERD was mainly generated from occipital cortex for both target and non-target conditions. Its magnitude was enhanced across widespread cortical regions (e.g., bilateral occipital, parietal, and frontal areas) in the target condition and was greater in high-frequency α-band. Finally, α-ERD difference between target and non-target conditions was not higher in visual than that in other control modalities. All these findings indicated that human high-frequency α-ERD reflects cognitive attention processes underlying reaction to oddball target stimuli regardless of stimulus modality.