Gamma synchronization increases during movement and scales with kinematic
parameters. Here, disease-specific characteristics of this synchronization and
the dopamine-dependence of its scaling in Parkinson’s disease are
investigated. In 16 patients undergoing deep brain stimulation surgery,
movements of different velocities revealed that subthalamic gamma power peaked
in the sensorimotor part of the subthalamic nucleus, correlated positively
with maximal velocity and negatively with symptom severity. These effects
relied on movement-related bursts of transient synchrony in the gamma band.
The gamma burst rate highly correlated with averaged power, increased
gradually with larger movements and correlated with symptom severity. In the
dopamine-depleted state, gamma power and burst rate significantly decreased,
particularly when peak velocity was slower than ON medication. Burst amplitude
and duration were unaffected by the medication state. We propose that
insufficient recruitment of fast gamma bursts during movement may underlie
bradykinesia as one of the cardinal symptoms in Parkinson’s disease