Figure 1.

(Color online) Illustration of EMG data preprocessing as optimized for the data recorded during FOG-provoking experiments. (A) Raw EMG signals recorded with electrode pairs for the right musculus gastrocnemius (blue) and the right musculus tibialis anterior (red) in a PD subject during normal walking (time: –4 to 0 s) and during a commanded stop (time: 0 to +1 s). A Hilbert transform and the analytic signal approach were applied to these data to derive (B) instantaneous amplitude, and (C) instantaneous frequency series. (D–F) Raw EMG and corresponding instantaneous amplitude and frequency series for a PD subject during walking (time: –4 to 0 s) and during FOG (time: 0 to +1 s). Note the significant difference in EMG between the stop and the FOG episode.