Transcranial ultrasound stimulation to human middle temporal complex improves visual motion detection and modulates electrophysiological responses
Christopher R. Butler, Edward Rhodes, Joseph Blackmore, Xinghao Cheng, Robert L. Peach, Michele Veldsman, Fintan Sheerin, Robin O. Cleveland
Brain Stimulation 2022, 15, 1236-1245 · 10.1016/j.brs.2022.08.022
Abstract
Background Transcranial ultrasound stimulation (TUS) holds promise as a novel technology for non-invasive neuromodulation, with greater spatial precision than other available methods and the ability to target deep brain structures. However, its safety and efficacy for behavioural and electrophysiological modulation remains controversial and it is not yet clear whether it can be used to manipulate the neural mechanisms supporting higher cognitive function in humans. Moreover, concerns have been raised about a potential TUS-induced auditory confound. Objectives We aimed to investigate whether TUS can be used to modulate higher-order visual function in humans in an anatomically-specific way whilst controlling for auditory confounds. Methods We used participant-specific skull maps, functional localisation of brain targets, acoustic modelling and neuronavigation to guide TUS delivery to human visual motion processing cortex (hMT+) whilst participants performed a visual motion detection task. We compared the effects of hMT+ stimulation with sham and control site stimulation and examined EEG data for modulation of task-specific event-related potentials. An auditory mask was applied which prevented participants from distinguishing between stimulation and sham trials. Results Compared with sham and control site stimulation, TUS to hMT+ improved accuracy and reduced response times of visual motion detection. TUS also led to modulation of the task-specific event-related EEG potential. The amplitude of this modulation correlated with the performance benefit induced by TUS. No pathological changes were observed comparing structural MRI obtained before and after stimulation. Conclusions The results demonstrate for the first time the precision, efficacy and safety of TUS for stimulation of higher-order cortex and cognitive function in humans whilst controlling for auditory confounds.
Abstract via europepmc.
Exposures
Exposure 1: TUS to human middle temporal complex (hMT+)
Target: extrastriate visual cortex — “human middle temporal complex (hMT+, also known as V5)”
Device: Sonic Concepts · Sonic Concepts Inc · H-107 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | 50pulse duration × PRF gives 50% | ✓✓✓ |
| Sonication duration (s) | 0.3 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | ⚑ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | 440 | ✓✓✓ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
A stimulation trial comprised a 300 ms burst applied at a 1 kHz pulse repetition frequency (PRF) and a 50% burst duty cycle (BDC). The main experiment was divided into three runs each of 90 trials and was run twice, once with TUS targeted at hMT+ and once at the control site (FFA), the order counterbalanced across participants; a maximum of 250 ultrasound stimulation bursts per brain site was imposed as a safety limit.
Flags from extraction
exposures[0].free_field.pressure_kpa— The ~3.5 MPa value is the transducer's calibrated maximum free-field output capability at 100V, not necessarily the pressure delivered during the experiment (amplifier voltages used in the study were up to 60V).blinding— Paper does not use the word 'blind' explicitly; coded as single-blind based on the described auditory-masking design, which the stimulation-detection task confirmed prevented participants from distinguishing stimulation from sham trials.sham_type— Design includes both a genuine inactive/no-output sham (sham trials, no TUS delivered) and an active control site (FFA received real TUS), so both sham_type categories are recorded; per the exposures rule, the FFA control-site stimulation is not given its own exposure entry.