Transcranial focused ultrasound to V5 enhances human visual motion brain-computer interface by modulating feature-based attention

Joshua Kosnoff, Kai Yu, Chang Liu, Bin He

Nature Communications 2024, 15 · 10.1038/s41467-024-48576-8

human healthyhealthyeeg megbehaviour

Abstract

A brain-computer interface (BCI) enables users to control devices with their minds. Despite advancements, non-invasive BCIs still exhibit high error rates, prompting investigation into the potential reduction through concurrent targeted neuromodulation. Transcranial focused ultrasound (tFUS) is an emerging non-invasive neuromodulation technology with high spatiotemporal precision. This study examines whether tFUS neuromodulation can improve BCI outcomes, and explores the underlying mechanism of action using high-density electroencephalography (EEG) source imaging (ESI). As a result, V5-targeted tFUS significantly reduced the error in a BCI speller task. Source analyses revealed a significantly increase in theta and alpha activities in the tFUS condition at both V5 and downstream in the dorsal visual processing pathway. Correlation analysis indicated that the connection within the dorsal processing pathway was preserved during tFUS stimulation, while the ventral connection was weakened. These findings suggest that V5-targeted tFUS enhances feature-based attention to visual motion.

Abstract via europepmc.

Specieshuman

Subjects25 participants

Sessions per subjectnot reported

Randomisedyes

Blindingnot reported

Sham / controlinactive transducer, active control site, sound only

Auditory controlsound only sham

Readout timingonline

Anaesthesianot applicable

Readoutseeg meg, behaviour — mVEP brain-computer-interface speller Euclidean letter error; EEG source imaging (N200 theta/alpha/beta/gamma power and inter-regional connectivity)

Direction of effectexcitatorytFUS to the geometric center of V5 (tFUS-GC) significantly reduced BCI speller Euclidean error and amplified N200 theta/alpha power in V5 and downstream in the dorsal (superior parietal) visual pathway compared to non-modulated, decoupled-sham and tFUS-GP conditions, consistent with enhanced feature-based visual-motion attention.

Adverse eventsnone observedA questionnaire assessing headache, neck pain, dental pain, nausea, dizziness, anxiety and abnormal muscle contractions was administered before and after each session; none of the subjects reported adverse symptoms after the sessions.

Exposures

Exposure 1: tFUS-GC: tFUS to the geometric center of V5

Target: extrastriate visual cortex — “geometric center of V5 (middle temporal complex)”
Device: Sonic Concepts · Verasonics, Kirkland, Washington, USA · H275 (128-element random array) ✓

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	700	✓✓✓
Pulse duration (ms)	0.2	✓✓✓
Pulse repetition frequency (Hz)	3,000	✓✓✓
Duty cycle (%)	not reportedpulse duration × PRF gives 60%
Sonication duration (s)	0.5	✓✓✓

Pressure and intensity, by domain
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)	200	✓✓✓
In-situ Isppa (W/cm²)	0.168	✓✓✓
In-situ Ispta (W/cm²)	0.101	✓✓✓

Protocol, in the paper’s words

tFUS pulsed for 140 cycles per pulse at 700 kHz (yielding 200 microsecond pulse duration), 1500 pulses per sonication at a 3 kHz PRF, giving a 500 ms sonication; 1-4 sonication repeats were applied per BCI epoch, with the first sonication beginning 100 ms before visual stimulus onset and additional sonications spaced equidistantly over the epoch.

Consistency checks: intensity pressure inconsistent in situ.

Flags from extraction

exposures[0].in_situ.method — Values are described as both measured through an ex-vivo skull sample and 'derated'; paper text explicitly labels the reported intensities as derated, so method is recorded as derating.
n_sessions_per_subject — Paper states a single ~3-hour cross-over session was intended to cover all four conditions, but does not give an explicit numeric count of sessions per subject.
randomised — Paper describes the design as 'predominantly randomized order' with two conditions prioritized for scheduling reasons, so randomisation was not strict for all subjects.