Induction of Human Motor Cortex Plasticity by Theta Burst Transcranial Ultrasound Stimulation

Abstract

Objective Transcranial ultrasound stimulation (TUS) is a promising noninvasive brain stimulation technique with advantages of high spatial precision and ability to target deep brain regions. This study aimed to develop a TUS protocol to effectively induce brain plasticity in human subjects. Methods An 80-second train of theta burst patterned TUS (tbTUS), regularly patterned TUS (rTUS) with the same sonication duration, and sham tbTUS was delivered to the motor cortex in healthy subjects. Transcranial magnetic stimulation (TMS) was used to examine changes in corticospinal excitability, intracortical inhibition and facilitation, and the site of plasticity induction. The effects of motor cortical tbTUS on a visuomotor task and the effects of occipital cortex tbTUS on motor cortical excitability were also tested. Results The tbTUS produced consistent increase in corticospinal excitability for at least 30 minutes, whereas rTUS and sham tbTUS produced no significant change. tbTUS decreased short-interval intracortical inhibition and increased intracortical facilitation. The effects of TMS in different current directions suggested that the site of the plastic changes was within the motor cortex. tbTUS to the occipital cortex did not change motor cortical excitability. Motor cortical tbTUS shortened movement time in a visuomotor task. Interpretation tbTUS is a novel and efficient paradigm to induce cortical plasticity in humans. It has the potential to be developed for neuromodulation treatment for neurological and psychiatric disorders, and to advance neuroscience research. ANN NEUROL 2022;91:238-252.

Abstract via europepmc.

Flags from extraction

• exposures[0].timing.pulse_duration_ms — List value 0.32 ms (rTUS tone-burst duration) is drawn from a separate sentence describing rTUS ('...PRF of 1,000Hz and duty cycle of 32%...'/Fig 2 legend 'tone-burst duration (TBD) of 0.32 milliseconds'); the quoted source_quote here covers the tbTUS value (20 ms).
• exposures[0].timing.pulse_repetition_frequency_hz — List value 1000 Hz (rTUS PRF) is drawn from the sentence describing the rTUS paradigm, reproduced in protocol_description; the quoted source_quote here covers the tbTUS value (5 Hz).
• exposures[0].timing.duty_cycle_pct — List value 32% (rTUS duty cycle) is drawn from the sentence describing the rTUS paradigm, reproduced in protocol_description; the quoted source_quote here covers the tbTUS value (10%).
• exposures[0].timing.sonication_duration_s — Paper explicitly defines 'total sonication duration' as the cumulative active (on-time) duration (8 s), distinct from the 80 s total protocol/train duration used to describe the repeating burst pattern; both figures are reported in the text (see protocol_description).
• exposures[1].target.terms — Occipital control target is defined only as the O1 EEG electrode position; not further localized to a specific visual subregion (e.g. V1), so classified generically as occipital_lobe.
• n_sessions_per_subject — Session count (3) reflects Experiment 2 (tbTUS/rTUS/sham tbTUS on separate days, at least 1 week apart, in the 15-subject subset); other sub-experiments (occipital control, coil-orientation, visuomotor task) enrolled overlapping subsets of the 20 subjects with different numbers of visits.
• blinding — Sham tbTUS was implemented by flipping the transducer so its inactive face contacted the scalp, but the paper does not explicitly state whether participants and/or assessors were blinded to condition.