Transcranial Focused Ultrasound Enhances Sensory Discrimination Capability through Somatosensory Cortical Excitation
Chang Liu, Kai Yu, Xiaodan Niu, Bin He
Ultrasound in Medicine & Biology 2021, 47, 1356-1366 · 10.1016/j.ultrasmedbio.2021.01.025
Abstract
Low-intensity transcranial focused ultrasound (tFUS) has emerged as a non-invasive brain neuromodulation tool with high spatial specificity. Previous studies attributed tFUS-enhanced sensory performance to the ultrasound-induced inhibitory neural effects. However, to date there is no direct evidence validating the neural mechanism underlying ultrasound-mediated somatosensory enhancement. In this study, healthy human subjects (N = 9) were asked to perform tactile vibration frequency discrimination tasks while tFUS was directed onto the primary somatosensory cortex. During this task, we simultaneously recorded 64-channel electroencephalography (EEG) signals and investigated the brain responses at both EEG sensors and source domains by means of electrophysiological source imaging (ESI). The behavioral results indicated that the subjects' discrimination ability was improved by tFUS with an increased percentage of correct responses. EEG and ESI results revealed that tFUS neuromodulation was able to improve sensory discrimination capability through excitatory effects at the targeted sensory cortex.
Abstract via europepmc.
Exposures
Exposure 1: tFUS to primary finger somatosensory cortex, UPRF 300 Hz
Target: primary somatosensory cortex — “primary finger somatosensory cortical area (S1)”
Device: Blatek · Blatek Industries, Inc. · AT31529 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 0.2 | ✓✓✓⚑ |
| Pulse repetition frequency (Hz) | 300 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 6% | ⚑ |
| Sonication duration (s) | 0.5 | ✓✓✓ |
| Free-field pressure (kPa) | 780.4 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 5.64 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 0.338 | ✓✓✓ |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 286 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 1.1 | ✓✓✓ |
| In-situ Ispta (W/cm²) | 0.0671 | ✓✓✓ |
Pulsed US (100 cycles per pulse at 0.5 MHz fundamental frequency) was delivered to the finger representation area of S1 at 100 ms before the onset of each vibration stimulus, with each sonication lasting 500 ms at a UPRF of 300 Hz. A sham US session used active acoustic transmission but with the transducer physically decoupled from the scalp by 4-6 cm, serving as both sham and auditory/EMI confound control. Session order (sham vs. UPRF 300 Hz) was randomized.
Consistency checks: intensity pressure inconsistent free field; intensity pressure inconsistent in situ.
Flags from extraction
exposures[0].timing.pulse_duration_ms— pulse duration (0.2 ms) computed from the paper's own stated cycles-per-pulse (100) divided by fundamental frequency (0.5 MHz), a unit conversion sanctioned for this field.exposures[0].unspecified_domain.pressure_kpa— the 780.4 kPa value is described as 'applied to the scalp' (measured with a real skull sample present, not in free water alone, and not explicitly said to be in the brain), so its domain is ambiguous; placed in unspecified_domain rather than free_field or in_situ.exposures[0].timing.duty_cycle_pct— duty cycle not explicitly stated by the paper (only cycles-per-pulse and UPRF given); not computed.