Figure 2.

MEG sensor-level spectrograms. A group-averaged spectrogram from the same gradiometer sensor (located near the left motor cortex) is shown for the TD children (A) and the children with CP (B). Time (ms) is represented on the x-axis with 0 signifying movement onset. Relative spectral power is expressed as a percentage difference from baseline, with the color legend shown to the right of the spectrograms. As shown in the respective figures, there was a beta (14 to 26 Hz) event related desynchronization (ERD) that was initiated 400 ms prior to the movement onset, which was sustained for ~400 ms after movement onset. Following movement termination, there was a notable post movement beta rebound (PMBR) from 600 to 1000ms. A prominent gamma (68–82 Hz) event related synchronization (ERS) was also time locked with the onset of the hand motor action. Comparison of the spectrograms suggests that the strength of the changes in the respective neural oscillations were notably weaker in the children with CP. Note that the time-frequency windows of interest were determined statistically from the data collapsed across the two groups.