High-gamma oscillations in the motor cortex during visuo-motor coordination: A tACS interferential study
E Santarnecchi1, A Biasella2, E Tatti2
1Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab. (Si-BIN Lab), University of Siena, Italy; Berenson-Allen Center for Non-Invasive Brain Stimulation, Beth Israel Medical Center, Harvard Medical School, Boston, MA, USA; Siena Robotics and Systems Lab. (SIRS-Lab), Engineering and Mathematics Department, University of Siena, Italy.
Background:
While the role of beta (∼20Hz), theta (∼5Hz) and alpha (∼10Hz) oscillations in the motor areas have been repeatedly associated with defined properties of motor performance, the investigation of gamma (∼40-90Hz) oscillatory activity is a more recent and still not fully understood component of motor control physiology, despite its potential clinical relevance for motor disorders.
Objective/Hypothesis:
We have implemented an online neuromodulation paradigm based on transcranial alternating current stimulation (tACS) of the dominant motor cortex during a visuo-motor coordination task. This approach would allow a better understanding of the role of gamma activity, as well as that of other oscillatory bands, and their chronometry throughout the task.
Methods:
We tested the effects of 5Hz, 20Hz, 60Hz (mid-gamma) 80Hz (high-gamma) and sham tACS on the performance of a sample of right-handed healthy volunteers, during a custom-made unimanual tracking task addressing several randomly occurring components of visuo-motor coordination (i.e., constant velocity or acceleration pursuits, turns, loops).
Results:
Data showed a significant enhancement of motor performance during high-gamma stimulation - as well as a trending effect for mid-gamma - with the effect being prominent between 200 and 500ms after rapid changes in tracking trajectory. No other effects during acceleration or steady pursuit were found.
Conclusions:
Our findings posit a role for high-frequency motor cortex gamma oscillations during complex visuo-motor tasks involving the sudden rearrangement of motor plan/execution. Such a "prokinetic" effect of high-gamma stimulation might be worth to be tested in motor disorders, like Parkinson's disease, where the switching between different motor programs is impaired.
