Bidirectional motor cortical excitability changes induced by decapulse transcranial ultrasound stimulation: A pilot study
Yasuo Terao, Daisuke Ito, Francesco Fisicaro, Tatsuya Mishima, Satomi Inomata-Terada, Kaoru Yuasa, Takahiro Osada, Yoshikazu Ugawa
Neuroscience Research 2026 · 10.1016/j.neures.2026.105055
Abstract
Patterned transcranial ultrasound stimulation (TUS) over the human primary motor cortex (M1) has been shown to induce lasting excitability changes, though typically unidirectional. We developed a novel patterned TUS protocol capable of inducing bidirectional after-effects in M1. Thirteen healthy participants were studied. Two protocols were used, both employing decapulse stimulation (DPS)-10 ultrasound pulses per burst-with identical ultrasound intensity, frequency (0.5 MHz), total and net sonication durations (400 s and 8 s). The protocols differed in pulse repetition frequency (200 Hz vs. 10 Hz) and duty cycle (40% vs. 2%). These were named DPS5 and DPS100, expected to induce excitatory and inhibitory after-effects. We assessed motor-evoked potentials (MEPs) via transcranial magnetic stimulation of the corticospinal tract neurons at the cortical level and their axons at the cervicomedullary junction brainstem level, as well as resting motor threshold (RMT), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and short-interval intracortical facilitation (SICF) before and after TUS. DPS5 enhanced cortical MEP amplitude, while DPS100 reduced it, with both effects lasting 60-90 min post-sonication. No significant changes were observed in brainstem MEP, RMT, SICI, ICF, or SICF. These results show that DPS protocols can induce long-lasting, bidirectional changes in motor cortical excitability without detectable changes in paired-pulse TMS measures of intracortical inhibition or facilitation, holding promise as a novel, clinically applicable mechanism for inducing motor cortex excitability changes.
Abstract via europepmc.
Exposures
Exposure 1: DPS5 and DPS100 over M1 hotspot
Target: primary motor cortex — “motor cortex hotspot (right FDI representation, left M1)”
Device: NeuroFUS · Sonic Concepts (sold by Brainbox) · NeuroFus CTX-500 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 2 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 200, 10swept | ✓✓✓⚑ |
| Duty cycle (%) | 40, 2swept | ✓✓✓⚑ |
| Sonication duration (s) | 400 | ✓✓✓⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 30 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 0.6, 12swept | ✓✓✓ |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | 670 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 13.88 | ✓✓✓ |
| In-situ Ispta (W/cm²) | not reported |
DPS5: 400-s train of ten 2-ms pulses repeated every 5 ms (PRF 200 Hz) as a decapulse, repeated at 1 Hz; DPS100: 2-ms pulses every 100 ms (PRF 10 Hz) for 4000 pulses. Net sonication 8 s in both; total time 400 s.
Flags from extraction
exposures[0].timing.duty_cycle_pct— Two protocols: DPS5 40% within each pulse train (5% for the repeated train, 2% overall), DPS100 2%; abstract lists 40% vs 2%exposures[0].timing.sonication_duration_s— Total stimulation 400 s but net sonication 8 s; 400 recorded as the train durationexposures[0].timing.pulse_repetition_frequency_hz— PRF 200 Hz (DPS5, within decapulse trains) and 10 Hz (DPS100)exposures[0].in_situ.method— Estimated intensity/pressure after skull modelled with k-Wave; text does not state explicitly that these are in situ values; MI 1.26 here vs 0.95 in Discussionblinding— Participants not blinded; data analysed by a blinded authorn_subjects— 13 in Experiment I; 3, 7 and 4 in later experiments