Endogenous modulation of low frequency oscillations by temporal

34 Recent studies have associated increasing temporal expectations with synchronisation 35 of higher frequency oscillations and suppression of lower frequencies. In this experiment, we 36 explore a proposal that low-frequency oscillations provide a mechanism for regulating 37 temporal expectations. We used a speeded go/no-go task, and manipulated temporal 38 expectations by changing the probability of target presentation after certain intervals. Across 39 two conditions, the temporal conditional probability of target events differed substantially at 40 the first of three possible intervals. We found that reactions times (RT) differed significantly 41 at this first interval across conditions, decreasing with higher temporal expectations. 42 Interestingly, the power of theta activity (4-8Hz), distributed over central midline sites, also 43 differed significantly across conditions at this first interval. Furthermore, we found a transient 44 coupling between theta phase and beta power after the first interval in the condition with high 45 temporal expectation for targets at this time point. Our results suggest that the adjustments in 46 theta power and the phase-power coupling between theta and beta contribute to a central 47 mechanism for controlling neural excitability according to temporal expectations. 48