Parameter-dependent cell-type specific effects of transcranial focused ultrasound stimulation in an awake head-fixed rodent model
Sandhya Ramachandran, Huan Gao, Eric Yttri, Kai Yu, Bin He
Journal of Neural Engineering 2025, 22, 026022 · 10.1088/1741-2552/adbb1f
Abstract
Objective. Transcranial focused ultrasound (tFUS) is a promising neuromodulation technique able to target shallow and deep brain structures with high precision. Previous studies have demonstrated that tFUS stimulation responses are cell-type specific, and specifically tFUS can elicit time-locked neural activity in regular spiking units (RSUs) that is sensitive to increases in pulse repetition frequency (PRF), while time-locked responses are not seen in fast spiking units (FSUs). These findings suggest a unique capability of tFUS to alter circuit network dynamics with cell-type specificity; however, these results could be biased by the use of anesthesia, which significantly modulates neural activities. Approach. In this study, we developed an awake head-fixed rat model specifically designed for simultaneous tFUS stimulation using a customized 128-element ultrasound array transducer, and recording of spiking data. Using this novel animal model, we examined a series of PRFs and burst duty cycles (DCs) to determine their effects on neuronal subpopulations without anesthesia. Main results. We observed cell type specific responses to varying PRF and DC in the awake setting as well as the anesthetized setting, with time locked responses observed in RSU and delayed responses in FSU. Anesthesia broadly was found to dampen responses to tFUS, and affected the latency of delayed responses. Preferred parameters for inducing time-locked responses appear to be 1500 Hz PRF and 60% DC. Significance. We conclude that despite some differences in response, isoflurane anesthesia is not a major confound in studying the cell-type specificity of ultrasound neuromodulation, but may affect studies of circuit dynamics and FSU. Our developed awake model will allow for future investigations without this confound.
Abstract via europepmc.
Exposures
Exposure 1: S1 tFUS, PRF and duty-cycle sweep
Target: primary somatosensory cortex — “S1 (primary somatosensory cortex)”
Device: Sonic Concepts · Sonic Concepts, Inc. · H276 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,500 | ✓✓✓ |
| Pulse duration (ms) | 0.04, 0.2, 0.4swept | ✓✓✓ |
| Pulse repetition frequency (Hz) | 30, 300, 1,500, 3,000, 4,500swept | ✓✓✓⚑ |
| Duty cycle (%) | 6, 30, 60swept | ✓✓✓ |
| Sonication duration (s) | 0.067 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 114 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 0.079 | ✓✓✓ |
| In-situ Ispta (W/cm²) | 0.0006, 0.00603, 0.0301, 0.0603, 0.0904swept | ✓✓✓⚑ |
Trials of 67 ms ultrasound duration were delivered every 2.5 s (10% jitter), 505 trials per parameter combination. PRF was swept (30, 300, 1500, 3000, 4500 Hz) at a fixed 200 microsecond tone-burst duration (TBD); PRF was then held at 1500 Hz while TBD was swept (40, 200, 400 microseconds), giving duty cycles of 6%, 30%, and 60%. A sham condition delivered the 1500 Hz PRF stimulus off-target toward the front of the skull.
Consistency checks: intensity pressure inconsistent in situ.
Flags from extraction
exposures[0].in_situ.ispta_w_cm2— ISPTA values across PRF conditions were calculated from a single measured peak-to-peak pressure via a pulse-intensity-integral formula, not independently measured for each PRF; the calculated value for 1500 Hz (30.13 mW/cm2) differs from the value the paper separately reports as directly measured for the same nominal condition (23.7071 mW/cm2, quoted under isppa_w_cm2).exposures[0].timing.pulse_repetition_frequency_hz— Source text reads '300 H' where '300 Hz' is clearly intended (likely OCR/typesetting error); recorded as 300 Hz.randomised— The paper states parameters were tested in random order within each animal (a within-subject design), not that subjects were randomised to groups; recorded as true but this may not map cleanly onto the randomised-groups sense of the field.auditory_control— Sham used real ultrasound delivered off-target rather than a named auditory-masking method; classified as 'other' since it does not match a listed auditory_control category.n_sessions_per_subject— Recordings occurred across multiple ages/months (PRF tests, anesthesia tests, DC tests) with 2-3 recordings per head-fixation session, but paper does not state a single total number of sessions per subject.