, 1998). The consistently very shallow slopes indicate that beta oscillations emerge with only small time delays throughout the cortical-BG network. Overall, our results are consistent click here with ∼20 Hz beta having a selective, distinct role in coordinating information processing within the BG of normal behaving animals. To explore beta timing in more detail, we examined trial-by-trial LFP traces during GO trials (Figure 3A). Epochs of high

beta power appeared to occur stochastically, with some task events either increasing (Cue) or diminishing (Side In) the probability of entering this beta state. Around detected movement onset (Nose Out) the pattern of beta power change was unexpectedly complex, showing a marked dependence on reaction time. For the most rapid responses, the beta ERS began around the time of movement

onset and peaked shortly afterwards (Figures 3A and 3B). On trials with slower responses, the beta ERS began well before movements and was mostly completed by movement onset. To quantify this phenomenon we compared beta power for fast- selleckchem versus slow-RT trials during the 300 ms epochs immediately preceding and following movement onset ( Figure 3B, top). In both epochs all subjects had a significant difference in beta power (paired t tests before Nose out: for 3 rats p < 10−4, for the other p = 0.024; after Nose out: p < 10−3 for all rats). In addition, we calculated

correlation coefficients between beta power and reaction time at each moment during task performance ( Figure 3B, bottom). A strong positive correlation was found about 750 ms after the Cue event, driven by the ERD that is maximal around movement completion (see Kühn et al., 2004 and Williams et al., 2005 for related observations in humans). In addition, a smaller but reliable correlation occurred ∼30–100 ms before movement initiation. This suggests that the presence of the high-beta state during a critical period delays movement onset, consistent with evidence in humans associating increased beta power Cell press with slower movements ( Levy et al., 2002, Brown et al., 2001, Chen et al., 2007 and Pogosyan et al., 2009). The Go/NoGo task variant (Figure 3C) is similar to the Immediate-Go task, except that there are three possible instruction cues: Go left, Go right, or hold in place (NoGo). As before, simply holding before the instruction cue was not associated with elevated beta. However, both Go and NoGo cues were similarly followed after several hundred milliseconds by a beta ERS (Figures 3D and 3E). This observation suggests that planning not to move is also associated with enhanced beta and confirms that the main beta ERS that we analyze here is not rigidly linked to either movement initiation or suppression. At the same time, we observed two interesting differences between GO and NOGO trials.