Movement-related synchronization of gamma activity is lateralized in patients with dystonia

There is evidence for synchronization at frequencies both under 30 Hz and over 60-80 Hz in the so-called gamma frequency band in patients with Parkinson's disease (PD). Gamma activity increases after dopaminergic therapy and during voluntary movement, suggesting that it might be physiological and relate to motor processing in the basal ganglia (BG). We recorded local field potential (LFP) activity during a choice reaction time task in 11 patients with dystonia undergoing implantation of the internal globus pallidus for therapeutic stimulation. The spectral content of the LFP was averaged with respect to movement onset over 6-11 Hz, 18-25 Hz and 60-80 Hz, separately for responses ipsilateral and contralateral to movement. There was a perimovement increase in 60-80 Hz activity in the LFP, but only contralateral to movement. In contrast, low-frequency LFP activity decreased symmetrically during movement. This occurred earlier in the 18-25 Hz band than in the 6-11 Hz band, and was followed by a postmovement increase in oscillatory activity in the 18-25 Hz band that was contralateral to movement. The presence of a lateralized movement-related increase in gamma activity in the BG of patients with dystonia, similar to that recorded in patients with treated PD, suggests that this may be a residual feature of normal BG function. Moreover, the results provide further support for functional distinctions between BG oscillatory activities of different frequency.