Effects of different sonication parameters of theta burst transcranial ultrasound stimulation on human motor cortex
Ke Zeng, Zhiwei Li, Xue Xia, Zhen Wang, Ghazaleh Darmani, Xiaoli Li, Robert Chen
Brain Stimulation 2024, 17, 258-268 · 10.1016/j.brs.2024.03.001
Abstract
Background Theta burst TUS (tbTUS) can induce increased cortical excitability in human, but how different sonication parameters influence the effects are still unknown. Objective To examine how a range of sonication parameters, including acoustic intensity, pulse repetition frequency, duty cycle and sonication duration, influence the effects of tbTUS on human motor cortical excitability. Methods 14 right-handed healthy subjects underwent 8 sessions with different tbTUS parameters in a randomized, cross-over design on separate days. The original tbTUS protocol was studied in one session and one parameter was changed in each of the seven sessions. To examine changes in cortical excitability induced by tbTUS, we measured the motor-evoked potential (MEP) amplitude, resting motor threshold, short-interval intracortical inhibition and intracortical facilitation, as well as short-interval intracortical facilitation before and up to 90 min after tbTUS. Results All conditions increased MEP amplitudes except the condition with low acoustic intensity of 10 W/cm 2 . Pulse repetition frequency of 5 Hz produced higher MEP amplitudes compared to pulse repetition frequencies of 2 and 10 Hz. In addition, higher duty cycles (5%, 10%, and 15%) and longer sonication durations (40, 80, and 120 s) were associated with longer duration of increased MEP amplitudes. Resting motor threshold remained stable in all conditions. For paired-pulse TMS measures, tbTUS reduced short-interval intracortical inhibition and enhanced short-interval intracortical facilitation, but had no effect on intracortical facilitation. Conclusions Ultrasound bursts repeated at theta (∼5 Hz) frequency is optimal to produce increased cortical excitability with the range of 2-10 Hz. Furthermore, there was a dose-response effect regarding duty cycle and sonication duration in tbTUS for plasticity induction. The aftereffects of tbTUS were associated with a shift of the inhibition/excitation balance toward less inhibition and more excitation in the motor cortex. These findings can be used to determine the optimal tbTUS parameters in neuroscience research and treatment of neurological and psychiatric disorders.
Abstract via europepmc.
Exposures
Exposure 1: tbTUS of left motor cortex, sweep of intensity/PRF/duty cycle/duration
Target: primary motor cortex — “left motor cortex (motor hotspot of right FDI)”
Device: Sonic Concepts · Sonic Concepts Inc. · H246 (custom two-element annular array) ✓
| Waveform | theta burst | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 10, 20, 30, 50swept | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2, 5, 10swept | ✓✓✓ |
| Duty cycle (%) | 5, 10, 15swept | ✓✓✓ |
| Sonication duration (s) | 40, 80, 120swept | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | ⚑ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | 1.13, 2.26swept | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | 0.11, 0.23, 0.34swept | ✓✓✓ |
The original tbTUS protocol was an 80 s train of 20 ms bursts of ultrasound repeated every 200 ms (AI=20 W/cm2, PRF=5 Hz, DC=10%, SD=80s). In 7 further sessions, one parameter was changed at a time (AI=10 W/cm2; PRF=2 or 10 Hz; DC=5% or 15%; SD=40 or 120 s), with tone-burst duration adjusted to maintain the stated duty cycle. Each of the 8 parameter sets was applied on a separate day, at least one week apart, in a randomised cross-over design.
Flags from extraction
exposures[0].free_field.isppa_w_cm2— Table 1's 'AI' column is the acoustic intensity set on the transducer power output system during calibration, not explicitly labelled as a measured free-field ISPPA/ISPTA value; left not_reported to avoid mislabelling a device setpoint as a measured free-field intensity.exposures[0].in_situ.isppa_w_cm2— In-situ ISPPA/ISPTA values are derived by applying a generic 75% skull-attenuation figure taken from a different prior study, not measured or individually simulated for these subjects.blinding— Paper describes a randomized cross-over design but does not state whether participants or assessors were blinded to the tbTUS parameter set used in each session.