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. 2020 May 19;9:e50654. doi: 10.7554/eLife.50654

Figure 9. Time course of the beta power and burst rate throughout trial performance and following reward feedback.

(A) Time course of the feedback-locked beta power during sequence performance in the learning blocks, shown separately for anx1, anx2 and control groups. Average across sensorimotor and prefrontal electrode regions as in panel (B). Shaded areas indicate the SEM around the mean. Participants completed sequence2 on average between 720 (30) and 5350 (100) ms, denoted by the top gray box. The STOP signal was displayed 7000 ms after the GO signal, and was followed at 9000 ms by the feedback score. This representation shows two distinct time windows of significant differences in beta activity between the anx1 and control groups: at the end of the sequence performance and subsequently following feedback presentation (PFDR<0.05,Δ=0.65,CI=[0.55,0.75], respectively, denoted by the purple bar at the bottom). Anx2 participants also exhibited an enhanced beta power towards the end of the sequence performance (PFDR<0.05,Δ=0.61,CI=[0.56,0.67]). (B) Time course of the rate of longer (>500 ms) oscillation bursts during sequence performance in the learning blocks. Anx1 participants exhibited a prominent rise in the burst rate 400–1600 ms following the feedback score, which was significantly larger than the rate in control participants (PFDR<0.05,Δ=0.82,CI=[0.70,0.91]). Data display the mean and ± SEM. The topographic map indicates the electrodes of significant effects for panels (A–C) (PFDR<0.05). (C) Same as panel (B) but showing the rate of shorter beta bursts (<300 ms) during sequence performance in the learning blocks. Between-group comparisons demonstrated a significant drop in the rate of brief oscillation bursts in anx1 participants relative to control participants at the beginning of the performance (PFDR<0.05,Δ=0.70,CI=[0.56,0.84]), but not after the presentation of the feedback score. In all panels, the traces of the mean power and burst rates were displayed after averaging across the significant sensorimotor and prefrontal electrodes shown in the inset in panel (B).

Figure 9.

Figure 9—figure supplement 1. Beta power spectral density and burst rate during reward-based learning.

Figure 9—figure supplement 1.

(A–C) During learning, the general level of normalized PSD did not differ between groups (PFDR>0.05). The learning-related PSD was normalized into decibels (dB) with the PSD of the initial resting state recording. (D) Probability distribution of beta-band oscillation-burst life-times within range 50–2000 ms for each group during learning blocks. The double-logarithmic representation suggests that longer-tailed distributions were observed in anx1 participants, although there were no between-group significant differences in the scaling exponent of the distribution τ (PFDR>0.05). Data are shown as mean and ± SEM across sensorimotor and prefrontal electrodes, corresponding with the inset with a topographic map. (E) Similar to panel (D), but for the representation of the burst distribution in anx2 and control participants across prefrontal electrodes, as shown in the inset. Participants in the anx2 group appeared to exhibit more frequent long bursts than controls in these prefrontal electrodes, but there were no between-group significant differences in the scaling exponents τ (PFDR>0.05).
Figure 9—figure supplement 2. Higher gamma band activity analysis rules out an explanation in which muscle artifacts influence feedback-related changes in power.

Figure 9—figure supplement 2.

Broadband high-frequency gamma band activity, above 50 Hz, has been linked to muscle artifacts (Muthukumaraswamy, 2013). To rule out the possibility that muscle artifacts could explain the feedback-locked beta activity differences between experimental and control groups, we assessed the gamma (50–100 Hz) power activity in different conditions. (A) Gamma power is shown for these intervals: within 0–1 s after feedback presentation, when participants should be at rest after completing the trial performance (green line); within 0–1 s locked to a key press, when participants are moving their fingers (orange line); within 0–1 s locked to the initiation of the trial, when participants are cued to wait for the GO response, and can be expected to be mentally preparing but otherwise at rest (black line). Gamma power was averaged across temporal electrodes, where artifacts usually lead to larger effects. No differences between conditions were found (P>0.05). (B) Same as panel (A) but after averaging the gamma power values across all sensorimotor (SM) channels. No significant differences were found here either. (C, D) Gamma power locked to the feedback presentation is displayed separately in experimental and control groups in temporal (C) and sensorimotor channels (D). No significant between-group differences were found. (E, F) Same as panels (C–D) but during the waiting interval, when participants were waiting to initiate the trial.