Image-Guided Transcranial Focused Ultrasound Stimulates Human Primary Somatosensory Cortex
Wonhye Lee, Hyungmin Kim, Yujin Jung, In-Uk Song, Yong An Chung, Seung-Schik Yoo
Scientific Reports 2015, 5 · 10.1038/srep08743
Abstract
Focused ultrasound (FUS) has recently been investigated as a new mode of non-invasive brain stimulation, which offers exquisite spatial resolution and depth control. We report on the elicitation of explicit somatosensory sensations as well as accompanying evoked electroencephalographic (EEG) potentials induced by FUS stimulation of the human somatosensory cortex. As guided by individual-specific neuroimage data, FUS was transcranially delivered to the hand somatosensory cortex among healthy volunteers. The sonication elicited transient tactile sensations on the hand area contralateral to the sonicated hemisphere, with anatomical specificity of up to a finger, while EEG recordings revealed the elicitation of sonication-specific evoked potentials. Retrospective numerical simulation of the acoustic propagation through the skull showed that a threshold of acoustic intensity may exist for successful cortical stimulation. The neurological and neuroradiological assessment before and after the sonication, along with strict safety considerations through the individual-specific estimation of effective acoustic intensity in situ and thermal effects, showed promising initial safety profile; however, equal/more rigorous precautionary procedures are advised for future studies. The transient and localized stimulation of the brain using image-guided transcranial FUS may serve as a novel tool for the non-invasive assessment and modification of region-specific brain function.
Abstract via europepmc.
Exposures
Exposure 1: FUS sonication of hand primary somatosensory cortex (S1)
Target: primary somatosensory cortex — “hand primary somatosensory cortex (S1)”
Device: other named manufacturer · Channel Industries ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 250 | ✓✓✓ |
| 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) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 3 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 1.5 | ✓✓✓ |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | 0.7 | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | 0.35 | ✓✓✓ |
The sonication session consisted of batches of sonication trials that were 3 s apart. Each trial provided a sinusoidal acoustic pressure wave of 250 kHz, operating at a tone-burst-duration of 1 ms with a pulse repetition frequency (PRF) of 500 Hz (i.e. duty cycle of 50%) and a sonication duration of 300 ms to elicit excitation in the S1. FUS (consisting of ~200 stimulation trials) was administered on the hand S1 of each hemisphere, one hemisphere at a time, in a randomized sequence, plus a separate sham-type FUS session.
Flags from extraction
sham_type— Sham described only as 'mimicked the experimental procedures without providing actual sonication'; the exact mechanism (powered off, blocked, etc.) is not specified.exposures[0].in_situ.isppa_w_cm2— A separate subset of subjects who underwent EEG recording (h13-h18) reported a different in-situ estimate (1.0 ± 0.4 W/cm2 Isppa); the value used here is the mean reported for the main cohort (n=24) in Table 2.n_sessions_per_subject— Paper describes bilateral sonication plus a separate sham session but does not state an explicit total number of sessions per subject.