Fig. 4.

Impact of amplitude threshold on %OVL and PSI: Illustrates the %OVL and PSI for beta bursts derived with a 50th (red) and 85th (green) percentile amplitude threshold for both pairs of sites (A,B: STN-iCtx; C,D: STN-cSTN). The %OVL (A and C, both corrected for the threshold specific overlapping by chance) is significantly greater for bursts derived with the 85th percentile amplitude threshold compared to those derived with the 50th percentile amplitude threshold (STN-iCtx: n = 17, p < .001; STN-cSTN: n = 18, p < .001). This is despite the reduced burst probability when a higher percentile threshold was used (supplementary fig. 8). Similarly, the PSI (B and D) for bursts derived with the 85th percentile amplitude threshold was greater than that derived with the lower amplitude threshold (STN-iCtx: n = 17, p = .009; STN-cSTN: n = 18, p = .009). The coupling ratios between long and short beta bursts derived from a selection of percentile amplitude thresholds (50th, 55th, 60th, 65th, 70th, 75th, 80th, 85th) are illustrated in E (Ratio OVL) and F (Ratio PSI). The positive median coupling ratios demonstrated in the box and whisker plots confirm that the stronger coupling in long as opposed to short beta bursts is preserved across different thresholds. Values presented as mean ± SEM. * p < .05, ** p < .01, *** p < .001; STN = ipsilateral subthalamic nucleus, cSTN = contralateral subthalamic nucleus; iCtx = ipsilateral motor cortex. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)