Figure 4.

Cortical-subthalamic coupling in the low-frequency band. (A) Percentage relative change of cortical-subthalamic low frequency (i.e. θ-α band, 4–13 Hz) coupling during gait freezing versus (effective) walking. During gait freezing (F_START – F_STOP), the cortex and the STN decoupled selectively in the hemisphere with less striatal dopamine (H−). The decoupling was already evident before gait freezing (F_PRE) and vanished with the recovery of a normal locomotor pattern (F_POST). (B) Percentage relative change of cortical-subthalamic low-frequency coupling during gait freezing versus successful passing through a door. The cortex and the STN in H− decoupled only during gait freezing (as in A) and not during successful passing through a door. (C) Percentage relative change of cortical-subthalamic low frequency coupling during gait freezing versus voluntary stop. The cortex and the STN (in H−) decoupled only during gait freezing (as in A) and not during voluntary stop. (D) Percentage relative change of cortical-subthalamic low frequency coupling during passing through a door in subjects with versus without FOG. Subjects with and without FOG showed the same cortical-subthalamic coupling during (effective) walking and successful passing through a door. Cx = cortex (i.e. SMA, M1 and PC); H = hemisphere (H+ and H− refer to the side with more and less striatal dopaminergic innervation, respectively); STN+ and STN− refers to the side with more and less striatal dopaminergic innervation, respectively; FOG+ and FOG− refers to the patients suffering or not suffering from FOG, respectively. The horizontal bars indicate statistical significance (P < 0.05). Of note, the statistical horizontal bars in A are not replicated in B and C, for clarity of the text.