Krembil Research Institute, University Health Network, Toronto, Canada
Kai-Hsiang Stanley Chen
Krembil Research Institute, University Health Network, Toronto, Canada; Department of Neurology, National Taiwan University Hospital Hsin-Chu Branch, Hsin-Chu, Taiwan
Jean-François Nankoo
Krembil Research Institute, University Health Network, Toronto, Canada
James Saravanamuttu
Krembil Research Institute, University Health Network, Toronto, Canada
Yanqiu Wang
Krembil Research Institute, University Health Network, Toronto, Canada
Mazen El-Baba
Krembil Research Institute, University Health Network, Toronto, Canada
Xue Xia
Division of Neurology, Department of Medicine, University of Toronto, Toronto, Canada
Shakthi Sanjana Seerala
Sunnybrook Research Institute, Toronto, Canada
Kullervo Hynynen
Sunnybrook Research Institute, Toronto, Canada
Andres M Lozano
Krembil Research Institute, University Health Network, Toronto, Canada; Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University of Toronto, Toronto, Canada
Robert Chen
Krembil Research Institute, University Health Network, Toronto, Canada; Division of Neurology, Department of Medicine, University of Toronto, Toronto, Canada
Low-intensity transcranial ultrasound (TUS) can non-invasively modulate human neural activity. We investigated how different fundamental sonication parameters influence the effects of TUS on the motor cortex (M1) of 16 healthy subjects by probing cortico-cortical excitability and behavior. A low-intensity 500 kHz TUS transducer was coupled to a transcranial magnetic stimulation (TMS) coil. TMS was delivered 10 ms before the end of TUS to the left M1 hotspot of the first dorsal interosseous muscle. Varying acoustic parameters (pulse repetition frequency, duty cycle, and sonication duration) on motor-evoked potential amplitude were examined. Paired-pulse measures of cortical inhibition and facilitation, and performance on a visuomotor task was also assessed. TUS safely suppressed TMS-elicited motor cortical activity, with longer sonication durations and shorter duty cycles when delivered in a blocked paradigm. TUS increased GABAA-mediated short-interval intracortical inhibition and decreased reaction time on visuomotor task but not when controlled with TUS at near-somatosensory threshold intensity.
