Transcranial focused ultrasound stimulation of human primary visual cortex
Wonhye Lee, Hyun-Chul Kim, Yujin Jung, Yong An Chung, In-Uk Song, Jong-Hwan Lee, Seung-Schik Yoo
Scientific Reports 2016, 6 · 10.1038/srep34026
Abstract
Transcranial focused ultrasound (FUS) is making progress as a new non-invasive mode of regional brain stimulation. Current evidence of FUS-mediated neurostimulation for humans has been limited to the observation of subjective sensory manifestations and electrophysiological responses, thus warranting the identification of stimulated brain regions. Here, we report FUS sonication of the primary visual cortex (V1) in humans, resulting in elicited activation not only from the sonicated brain area, but also from the network of regions involved in visual and higher-order cognitive processes (as revealed by simultaneous acquisition of blood-oxygenation-level-dependent functional magnetic resonance imaging). Accompanying phosphene perception was also reported. The electroencephalo graphic (EEG) responses showed distinct peaks associated with the stimulation. None of the participants showed any adverse effects from the sonication based on neuroimaging and neurological examinations. Retrospective numerical simulation of the acoustic profile showed the presence of individual variability in terms of the location and intensity of the acoustic focus. With exquisite spatial selectivity and capability for depth penetration, FUS may confer a unique utility in providing non-invasive stimulation of region-specific brain circuits for neuroscientific and therapeutic applications.
Abstract via europepmc.
Exposures
Exposure 1: Transcranial FUS to primary visual cortex (V1), image-guided
Target: primary visual cortex — “primary visual cortex (V1)”
Device: custom-built · MR-compatible single-element FUS transducer (focal length 3 cm; focus 3 mm diameter x 17 mm length, FWHM)
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 270 | ✓✓✓ |
| Pulse duration (ms) | 1 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 500 | ✓✓✓ |
| Duty cycle (%) | 50pulse duration × PRF gives 50% | ✓✓✓ |
| Sonication duration (s) | 0.3 | ✓✓✓ |
| Free-field pressure (kPa) | 1,480 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 16.6 | ✓✓✓ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | 3 | ✓?⚑ |
| In-situ Ispta (W/cm²) | 1.5 | ✓✓✓ |
Event-related fMRI was conducted during three conditions (FUS, sham FUS, photic stimulation); the 300-ms long stimulation was given 50 times every 13 s, synchronized with the MR scanner. In a separate EEG session outside the MRI (a subset of 10 participants), stimulation (FUS, sham FUS, or photic) was given 50 times every 2.5 s, with resting-state and sham FUS as additional conditions; condition order was randomized and balanced across participants.
Consistency checks: intensity pressure inconsistent free field.
Flags from extraction
n_sessions_per_subject— All 19 participants had one FUS-fMRI session; a subset of 10 participants additionally underwent a separate FUS-EEG session, so sessions per subject were either 1 or 2 depending on participation in the EEG arm.randomised— Randomisation described ('these conditions were randomized and balanced across the participants') refers to within-subject ordering of FUS/sham/photic conditions, not allocation to separate treatment groups.exposures[0].in_situ.isppa_w_cm2— Reported as a mean +/- SD across 19 subjects (0.7-6.6 W/cm2 range, mean 3.0+/-1.7); the mean is recorded per schema convention and the quote carries the full spread.