Desynchronization α frequency event-related in visual selective attention requiring tasks

Comparative analysis of the EEG amplitude depression in the α band has been performed in two paradigms varying in the degree of involvement of functionally different attention processes: visual search for the relevant stimulus (RS) among many irrelevant stimuli (iRS) and oddball. Simple visual examination of several identical stimuli was used as a control for the visual search task. The method of videooculography was used for verification of gaze direction during RS search. The EEG dynamics in the α band (desynchronization, D) was considered to be a correlate of attention processes. The visual search task performance revealed considerably higher D after RS finding compared to the control. The higher degree of D during the search seems to be due to the higher complexity of the task and complexity of visual environment. The D in the frontal regions, which has the greatest amplitude, supposedly reflects the performance of an adequate motor performance program under the control of voluntary (top-down) attention. At the same time, the D in the occipital and parietal areas seems to reflect the processes of involuntary attention activated due to the change in visual information (the finding of the only RS among numerous iRS). In the oddball task, presentation of both RS and iRS also induced D, which proved to be more marked in response to RS and maximal in the visual areas. We suppose that D under oddball reflects the involvement of involuntary attention. © 2011 Pleiades Publishing, Ltd.