A Noninvasive Focused Ultrasound-Evoked Electrophysiological Mapping Method With High Spatiotemporal Precision
Ye Yuan, Jie Zhao, Tian Liu, Jue Wang
IEEE Transactions on Biomedical Engineering 2026 · 10.1109/tbme.2025.3612200
Abstract
Achieving noninvasive functional brain mapping with submillimeter spatial and millisecond temporal resolution remains a major technical challenge. Existing modalities fail to meet both requirements simultaneously: fMRI offers high spatial resolution but suffers from hemodynamic delays, while EEG provides superior temporal resolution yet lacks spatial specificity. We present a cortical mapping method that integrates focused ultrasound (FUS) stimulation with local field potential (LFP) recordings for high-resolution electrophysiological mapping. A 5 × 5 Cartesian scanning grid was applied over the barrel cortex. FUS pulses (4 MHz, 1.6 MPa peak negative pressure, 1Hz pulse repetition frequency) were sequentially delivered to each grid point, and peak LFP amplitudes were recorded at each site via a tungsten microelectrode to generate activation heatmap. Our method achieved approximately 0.45 mm spatial resolution and 10 ms temporal resolution in detecting FUS evoked LFP responses. The proposed FUS-LFP mapping paradigm enables high-resolution and time-precision visualization of cortical electrophysiological responses to noninvasive stimulation. This method provides a robust and scalable approach for probing evoked cortical responses and constructing functional brain maps, with promising translational relevance for preclinical neuroengineering.
Abstract via pubmed.
Exposures
Exposure 1: FUS mapping of C2 barrel column, primary somatosensory cortex (exposed dura, craniotomy)
Target: primary somatosensory cortex — “C2 whisker barrel (bbl) column, left primary somatosensory cortex”
Device: other named manufacturer · Siansonic, Inc. · HIFU ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 4,000 | ✓✓✓ |
| Pulse duration (ms) | 1 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 1 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 0.1% | |
| Sonication duration (s) | not reported | ⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 400, 800, 1,200, 1,600swept | ✓?⚑ |
| Ispta, domain unspecified (W/cm²) | 0.083 | ✓✓✓ |
FUS was sequentially delivered to each of 25 spatial coordinates in a 5x5 scanning grid (0.2 mm step size) over the C2 barrel column, with 10 pulses per stimulation site; each site was stimulated twice and the response averaged. A preliminary multi-pressure experiment applied four pressure levels (0.4, 0.8, 1.2 and 1.6 MPa) in a randomized sequence at the same site, each repeated 10 times, before final parameters (1.6 MPa PNP, 1 ms pulse width, 1 Hz PRF, 10 pulses) were selected for the main mapping experiment.
Flags from extraction
exposures[0].unspecified_domain.pressure_kpa— Pressures (0.4-1.6 MPa PNP) are stated without specifying whether they are free-field (water-tank calibrated) or in-situ values; the transducer was aimed directly at the exposed dura through a craniotomy (no skull in the path), but the paper does not explicitly label the delivered PNP by domain, so it is recorded as unspecified_domain.device.family— The transducer manufacturer (Siansonic, Inc.) is a named commercial maker not covered by the specific vocabulary entries; classified as commercial_other.exposures[0].timing.sonication_duration_s— Only pulse count (10 pulses per site) and PRF (1 Hz) are given; total sonication duration per site is not explicitly stated and was not computed.randomised— Randomization refers to the order of the four pressure levels tested in the single-rat pilot experiment ('applied in a randomized sequence'), not group allocation across the 10-rat cohort.