Figure 1.

Methods in online experiment. A, The analog LFP signal was filtered around the individual's beta peak frequency (Table 1). The signal was rectified and smoothed (200 ms time constant) to obtain the envelope of the beta signal. To define beta bursts a threshold was set at the 75th percentile of the beta amplitude (red line). The onset of a burst was defined as when the rectified signal crossed the threshold amplitude and the end of the burst defined as when the amplitude fell below threshold. The minimum burst duration was defined as 100 ms. B, The go-cue for the behavioral experiment was triggered according to four conditions. Condition 1–3 were aligned to the beta burst timing. In Condition 1 the go-cue was presented 100 ms after the onset of beta bursts. The waiting period of 100 ms was necessary to capture bursts as previously defined. In Condition 2 the go-cue was presented at the end of the bursts. In Condition 3 the go-cue was presented at the end of the bursts +200 ms. In Condition 4 the go-cue was presented without any fixed temporal relationship to beta bursts (see Materials and Methods). C, The behavioral part of the experiment. The subject controlled the red cursor with a manual joystick and was instructed to perform a ballistic movement in the direction of the go-cue (green target). The intertrial interval was 7 s plus up to a 2.5 s burst detection period necessary to meet one of the randomly assigned Conditions 1–3 (B). For each condition a number of 60 trials were aimed for.