A range of pulses commonly used for human transcranial ultrasound stimulation are clearly audible
Ainslie Johnstone, Tulika Nandi, Eleanor Martin, Sven Bestmann, Charlotte Stagg, Bradley Treeby
Brain Stimulation 2021, 14, 1353-1355 · 10.1016/j.brs.2021.08.015
Exposures
Exposure 1: TUS over the inion (Experiments I-IV, pooled)
Target: primary visual cortex — “positioned over the inion”
Device: Sonic Concepts · Sonic Concepts · H115-2AA ✓
| Waveform | pulsed, continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 270 | ✓✓✓ |
| Pulse duration (ms) | not reported | ⚑ |
| Pulse repetition frequency (Hz) | 500, 250, 125swept | ✓✓✓ |
| Duty cycle (%) | 50swept | ✓✓✓ |
| Sonication duration (s) | 0.3, 0.15swept | ✓✓✓ |
| Free-field pressure (kPa) | 700 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 16 | ✓✓✓ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | 230 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 1.7 | ✓✓✓ |
| In-situ Ispta (W/cm²) | not reported |
Four experiments manipulated pulse ramping, PRF and continuous-vs-pulsed stimulation to test audibility. Expt I (n=7): 300 ms stimulus, 50% duty cycle, 500 Hz or 250 Hz PRF, with 0, 0.5 or 1 ms ramps applied to the start/end of each pulse (pulse on-time adjusted to keep time-averaged intensity constant). Expt II (n=7): as Expt I but 125 Hz PRF with 0, 1 or 2 ms ramps. Expt III (n=6): continuous 150 ms stimulation with or without a 20 ms ramp. Expt IV (n=6): active and sham pulses masked with an intermittent 1 s square-wave audio mask matching the PRF, played over headphones.
Flags from extraction
exposures[0].target.terms— Target region is not explicitly named in this short communication; inferred as primary visual cortex from the inion-based transducer positioning and the cited companion paper (Gimeno et al., ref [8]) describing 270 kHz stimulation of primary visual cortex by the same group.exposures[0].timing.pulse_duration_ms— Only PRF and duty cycle are stated for the pulsed experiments; individual pulse duration is not stated and was not computed (per extraction rule against deriving one timing number from another).exposures[0].timing— Four distinct experiments (I-IV) with different PRF, ramp duration and waveform were combined into one exposure (same target/frequency) with list-valued timing fields, per the target-times-frequency exposure rule; see protocol_description for per-experiment detail.sham_type— Paper states stimulation was 'randomised and double-blind' with sham trials but does not describe how the sham was generated, beyond thanking Sonic Concepts for 'technical modifications to the TPO that allowed ramping and sham conditions'.readout_timing— Participants reported audition 'on every trial using a mouse click'; exact timing relative to stimulus onset/offset is not detailed, classified as online.n_sessions_per_subject— Participants 'took part in one or more experiments across multiple days' but the paper does not state a specific number of sessions per subject.
Notes: Short communication (methodological/auditory-confound study), not a neuromodulation efficacy study; direction_of_effect is therefore not_assessed. Free-field pressure/intensity (700 kPa, 16 W/cm2) and derated in-brain estimates (230 kPa, 1.7 W/cm2, via 9.8 dB insertion loss) are constant across all four experiments; only timing parameters varied by experiment.