Fig. 1.

Diagram of the overall experimental setup. The voluntary right foot pedaling generates the motion signal, and only the onset of this motion signal (from a fast-response, high-precision comparator) is detected as the trigger signal for transmitting transcranial focused ultrasound (tFUS) onto the primary leg motor area. The concurrent 64-channel electroencephalogram (EEG) is recorded for electrophysiological source imaging (ESI). The reconstructed source activity at the leg motor cortical area is further extracted and the movement-related cortical potential (MRCP) source profiles are thus derived for further assessing the tFUS neuromodulatory effects. The electromyogram (EMG) is recorded simultaneously for monitoring and validating successful voluntary foot pedaling trials. The subject is instructed to wear earplugs throughout each testing session.