Transcranial Focused Ultrasound Enhances the Discriminative Power of Targeted Voluntary Motor Signals in Humans

Transcranial focused ultrasound (tFUS) is an emerging neuromodulation technique with high spatial specificity and deep brain penetration, but its effects on upper-limb voluntary motor signals relevant to brain-computer interfaces (BCIs) remain unknown. In this study, we investigated whether tFUS targeted at the motor cortex can enhance movement-related cortical potentials (MRCPs) and improve the discriminability of hand grasp signals. Eighteen healthy participants performed visually-cued left and right hand grasps while EEG and EMG were recorded during three condition types: left motor cortex-targeted tFUS, right prefrontal cortex-targeted tFUS, and a non-modulated baseline. Ultrasound pulse trains were delivered time-locked to movement cues using pulse repetition frequencies (PRFs) of 30 and 3000 Hz and duty cycles of 30% and 60%. Left motor cortex-targeted tFUS significantly amplified both MRCP amplitude and signal discriminability for BCI classification relative to both spatial sham and non-modulated conditions. Neither MRCP amplification nor BCI classification accuracy were found to change with the investigated PRFs or duty cycles. These findings demonstrate that tFUS can selectively enhance voluntary motor cortical signals and improve motor EEG-based BCI performance.