Ramped V1 transcranial ultrasonic stimulation modulates but does not evoke visual evoked potentials

Tulika Nandi, Ainslie Johnstone, Eleanor Martin, Catharina Zich, Robert Cooper, Sven Bestmann, Til Ole Bergmann, Bradley Treeby, Charlotte J. Stagg

Brain Stimulation 2023, 16, 553-555 · 10.1016/j.brs.2023.02.004

human healthyhealthyeeg meg

Specieshuman

Subjects14 participants

Sessions per subjectnot reported

Randomisedyes

Blindingdouble

Sham / controlundescribed

Auditory controlramped pulses

Readout timingonline

Anaesthesianot applicable

Readoutseeg meg

Direction of effectmixed or unclearTUS alone did not evoke potentials in the TUS-only blocks. In the checkerboard blocks, the N75 VEP component amplitude was larger for real TUS than no-TUS trials, but there was no significant difference between real and sham TUS trials directly.

Adverse eventsnot reported

Exposures

Exposure 1: Ramped TUS to left V1

Target: primary visual cortex — “primary visual cortex (V1)”
Device: Sonic Concepts · Sonic Concepts · H115-2AA ✓

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	270	✓✓✓
Pulse duration (ms)	3.25	✓✓✓
Pulse repetition frequency (Hz)	250	✓✓✓
Duty cycle (%)	50pulse duration × PRF gives 81.25%, which disagrees with the stated value	✓✓✓⚑
Sonication duration (s)	0.3	✓✓✓

Pressure and intensity, by domain
Free-field pressure (kPa)	700	✓✓✓
Free-field Isppa (W/cm²)	16	✓✓✓
Free-field Ispta (W/cm²)	not reported
In-situ estimate	not reported
In-situ pressure (kPa)	not reported
In-situ Isppa (W/cm²)	not reported
In-situ Ispta (W/cm²)	not reported

Protocol, in the paper’s words

Ramped pulses (1 ms Tukey ramp, 3.25 ms total pulse duration) were applied at a PRF of 250 Hz, with a pulse train duration of 300 ms and an effective duty cycle of 50%. In two TUS-only blocks, real and sham pulses (100 each) were applied randomly at a fixed inter-stimulus interval of 2 s; in two TUS checkerboard blocks, every fourth checkerboard flip (flipped every 0.5 s) was paired with a real or sham TUS trial (100 each), with the TUS trial starting 130 ms (±0-5 ms jitter) before the checkerboard flip.

Flags from extraction

sham_type — Paper does not describe the mechanism used to generate sham TUS pulses in this V1 study.
exposures[0].timing.duty_cycle_pct — Stated duty cycle (50%) and PRF (250 Hz) imply a 2 ms pulse, but the stated total pulse duration is 3.25 ms (including a 1 ms Tukey ramp); recorded as stated, not recomputed.
direction_of_effect — Real TUS increased N75 VEP amplitude relative to no-TUS trials, but real vs sham TUS trials were not significantly different, leaving the auditory-confound-free effect unclear.