Investigating the effects of pre-stimulus cortical oscillatory activity on behavior

Rhythmic brain activity may provide a functional mechanism that facilitates dynamic interareal interactions and thereby give rise to complex behavior. It has been shown that low and high frequency oscillations propagate in opposite directions, but interactions between brain areas in various frequency bands are poorly understood. We investigated local and long-range synchrony in a brain-wide network and their relation to behavior, while human subjects executed a variant of the Simon task during MEG recording. We hypothesized that the behavioral difference for stimulus-response congruent (C) and incongruent (IC) trials is caused by differences in cortical synchrony, and that the relative behavioral benefit for trials following instances with the same stimulus-response contingency (i.e. the Gratton effect) is caused by contingency-induced changes in the state of the network. This would be achieved by temporarily upregulating the connectivity strength between behaviorally relevant network nodes. We identified regions-of-interest that differed in local synchrony during the response phase of the Simon task. Within this network, spectral power in none of the nodes in either of the studied frequencies was significantly different in the pre-cue window of the subsequent trial. Nor was there a significant difference in coherence between the task-relevant nodes that could explain the superior performance after compatible consecutive trials.