High-gamma oscillations in the motor cortex during visuo-motor coordination: A tACS interferential study.
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
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.
Department 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. Electronic address: esantarn@bidmc.harvard.edu.
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Santarnecchi
Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab. (Si-BIN Lab), University of Siena, Italy.
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Biasella
Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab. (Si-BIN Lab), University of Siena, Italy.
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Tatti
Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab. (Si-BIN Lab), University of Siena, Italy.
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Rossi
Siena Robotics and Systems Lab. (SIRS-Lab), Engineering and Mathematics Department, University of Siena, Italy.
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Prattichizzo
Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, Brain Investigation & Neuromodulation Lab. (Si-BIN Lab), University of Siena, Italy; Department of Medicine, Surgery and Neuroscience, Human Physiology Section, University of Siena, Italy.
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Rossi
D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*
Entrainment; Gamma oscillations; Motor control; Motor cortex; Visuo-motor coordination; tACS