Supplementary Motor Area Activity Differs in Parkinson’s Disease with and without Freezing of Gait

Figure 1

(a) Time-frequency comparison. Each time-frequency decomposition plot is made up of the average activity for each group from the Cz channel, which is close to the primary motor cortex. The x-axis represents the time 1500 ms before and 1500 ms after movement onset. The y-axis represents each frequency bin. Dark colored spots indicate event-related desynchronizations, while light colored spots correspond to event-related synchronizations. The rightmost plot depicts the intertrial coherence, with light color representing periods of significance between group trials. The PD group shows significantly less alpha and low-beta desynchronization at the motor cortex about 315 ms after the start of normal walking as compared to HC. Randomization testing supports this finding with for the comparison of frequency bins starting at 6 Hz and going to 12 Hz, 315 ms after the start of normal walking. (b, c) In these plots, the magnitude of the event-related desynchronization is marked by a negative value on the y-axis. Each PD-HC pair shown constitutes a statistically significant difference in the canonical band group with respect to time, with the red vertical line indicating the onset of walking. (b) Event-related desynchronization in the alpha band is significantly decreased for the PD group at 364 ms before onset and at 315 ms after onset. (c) Likewise, event-related desynchronization at the beta band is significantly decreased for the PD group compared with the HC group, 364 ms before onset and 315 and 705 ms after onset. (d) Averaged (Cz-C3) movement-related cortical potentials (MRCP) between 5 subjects for each group. Both definite and probable groups show significantly less late BP and fpMP in preparation and during the execution of normal walking, compared with HC. (e) The average frontal peak of motor potential is most largely reduced in the definite compared with the probable group and HC group.

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