Alpha and beta changes in cortical oscillatory activity in a go/no go randomly-delayed-response choice reaction time paradigm

Objective: Predictable movements induce oscillatory changes over the contralateral motor cortex that begin before the movement, but their significance has not been fully established. We studied non-phase-locked changes in cortical oscillatory activity in a S1-centred double-stimulus go/no go paradigm with random interstimulus interval. Methods: About 58 reference-free EEG channels were analyzed by means of Gabor transforms in a group of 10 healthy subjects. A 2000 Hz tone (S1go, 84% probability) indicated the subject to make a brisk wrist extension after a second 2000 Hz tone (S2go). The S1-S2 interval was either 1.5, 3 or 4.5 s. A 1000 Hz tone (SI no go, 16% probability) indicated the subject not to move (and wait for another S1 tone). Results: A frontal 15 Hz synchronization was observed after S I in all conditions. No further significant changes were observed in the no go condition. A small pre-S2 alpha and beta desynchronization could be observed only in the 3 and 4.5 s-interval go conditions, being larger in the latter. Conclusions: These results suggest that the predictability of the timing of a movement influences the appearance of the pre-movement oscillatory changes; not only motor planning (the 'go' decision) is necessary, but also an estimation of when to move. Significance: Our findings provide new insight on the relationship between the decision-making process, movement, and cortical oscillatory activity. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.