A double-blind replication attempt of offline 5Hz-rTUS-induced corticospinal excitability
Po-Yu Fong, Benjamin R. Kop, Carys Evans, Vidya Gani Wijaya, Yongling Lin, Drew Cappotto, Jenny S.A. Lee, Anna Latorre, Joy Song, Bradley Treeby, Eleanor Martin, John Rothwell, Lennart Verhagen, Sven Bestmann
Imaging Neuroscience 2025 · 10.1162/imag.a.1046
Abstract
Transcranial ultrasound stimulation (TUS) is a promising new form of non-invasive neuromodulation. As a nascent technique, replication of its effects on brain function is important. Of particular interest is offline 5 Hz repetitive TUS (5 Hz-rTUS), originally reported by Zeng et al. (2022) to elicit lasting corticospinal excitability increases, with large effect sizes. Here, we conducted a pre-registered (https://osf.io/p5n4q) replication of this protocol that benefited from three additional features: double-blind application of TUS, neuronavigation for consistent TMS positioning, and individualised 3D acoustic simulations to assess M1 target exposure to TUS. Changes in resting motor thresholds (rMT), motor-evoked potential (MEP) amplitude, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) in response to TUS (5 Hz-rTUS vs. sham) were measured in the right first dorsal interosseous (FDI), abductor digiti minimi (ADM), and abductor pollicis brevis (APB) muscles. Transducer location was determined by the TMS-hotspot for motor representations of the right FDI, as in the original work. No significant effects of 5 Hz-TUS (vs. sham) were observed. Post-hoc simulations showed considerable variability of the acoustic focus, which was outside the anatomical M1-hand area in 67% of participants-in line with the known poor correspondence of TMS-hotspot location and M1-hand area. Our results indicate that the effect sizes of the neuromodulatory effects of 5 Hz-rTUS on M1 may be more variable than previously appreciated. We suggest that double-blinding, neuronavigated TMS, individualised acoustic simulations for TUS targeting and pre-registration will aid reproducibility across studies.
Abstract via europepmc.
Exposures
Exposure 1: 5 Hz-rTUS to left M1 (TMS-hotspot based)
Target: primary motor cortex — “left primary motor cortex (M1)”
Device: NeuroFUS · Sonic Concepts (sold by Brainbox) · NeuroFUS TPO with CTX-500-025 four-element annular array ✓
| Waveform | theta burst | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 20 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 5 | ✓✓✓ |
| Duty cycle (%) | 10pulse duration × PRF gives 10% | ✓✓✓ |
| Sonication duration (s) | 80 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 10 | ✓✓✓⚑ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | 1.2 | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | not reported |
80-s train of 20-ms ultrasound pulses repeated every 200 ms (PRF 5 Hz; 10% duty cycle), 400 pulses; TMS measures at baseline, 5, 30 and 60 min after sonication.
Flags from extraction
exposures[0].timing.waveform— Paper says 5 Hz-rTUS is 'also referred to as theta-burst TUS (tbTUS)' but the protocol is a single-level 5 Hz pulse train; could equally be 'pulsed'.sham_type— A sham session is delivered (double-blind, TPO display hidden) but how sham output was produced is not described in the text.exposures[0].in_situ.isppa_w_cm2— Mean of per-participant k-Plan simulations (1.20 +/- 0.43 W/cm2); the estimated 2.5 W/cm2 from 75% attenuation is not recorded here.exposures[0].free_field.isppa_w_cm2— Isppa in free water is described as 'set to' 10 W/cm2 via the TPO; Table 1 labels it free-water Isppa.