Effects of online motor cortex transcranial ultrasound stimulation on interhemispheric inhibition
Yanqiu Wang, Ke Zeng, Anton Fomenko, Xue Xia, Mandy Yi Rong Ding, Jean‐François Nankoo, Robert Chen
The Journal of Physiology 2026 · 10.1113/jp290803
Abstract
Transcranial ultrasound stimulation (TUS) of the motor cortex (M1) has been found to modulate interhemispheric inhibition (IHI) after sonication (offline effect). However, the effects of M1 TUS on IHI during sonication (online effect) remain unknown. The current study examined the effects of online M1 TUS on IHI from the sonicated M1 to the contralateral M1 and on the contralateral M1 excitability in 15 healthy subjects. IHI was measured with paired-pulse transcranial magnetic stimulation (TMS) at 10 ms (short-latency IHI, SIHI) or 40 ms (long-latency IHI, LIHI) interstimulus interval (ISI), and the contralateral M1 excitability was measured with single-pulse TMS. The results showed that online TUS decreased the sonicated M1 to the contralateral M1 at LIHI but not at SIHI, while the contralateral TUS M1 excitability was unchanged. TUS may modulate complex circuits that mediate LIHI. These findings showed that TUS can be used to investigate the functional interactions between the two hemispheres. KEY POINTS: Offline non-invasive brain stimulations have been shown to modulate interhemispheric inhibition. The current study examined the effects of online primary motor cortex (M1) transcranial ultrasound stimulation (TUS) on interhemispheric inhibition from the sonicated M1 to the contralateral M1, and the contralateral M1 excitability. TUS decreased long- but not short-latency interhemispheric inhibition from the sonicated M1 to the contralateral M1. TUS could be a tool for investigating functional interactions between the two hemispheres.
Abstract via europepmc.
Exposures
Exposure 1: Online right M1 TUS (500 ms, with TMS conditioning pulse at 490 ms)
Target: primary motor cortex — “right M1”
Device: Sonic Concepts · Sonic Concepts Inc. · custom two-element annular array H246; TPO201-80 driver ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | not reportedimplied by duty cycle ÷ PRF: 0.1 ms (not stated by the paper) | ⚑ |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | 10 | ✓✓✓ |
| Sonication duration (s) | 0.5 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 11.73 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 1.17 | ✓✓✓ |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | 2.93 | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | 0.29 | ✓✓✓ |
Sonication depth 30 mm, 20 W, 1000 Hz PRF, 10% duty cycle and 500 ms duration; a TMS conditioning pulse was delivered 10 ms before the end of sonication (SIHI) or TS at end or 30 ms after; 5 s intertrial interval.
Flags from extraction
exposures[0].in_situ.isppa_w_cm2— In situ values are estimated by assuming 75% skull attenuation (derating), not measured through skull.n_subjects— 18 recruited, 3 withdrawn for high TMS motor threshold; 15 analysed and recorded.n_sessions_per_subject— Experiments 1-3 are described within a 2.5-3 h visit; number of sessions across experiments not clearly stated.exposures[0].timing.pulse_duration_ms— Pulse duration not stated (duty cycle and PRF given only).