Ultrasound does not activate but can inhibit in vivo mammalian nerves across a wide range of parameters

Abstract

Ultrasound (US) has been shown to stimulate brain circuits, however, the ability to excite peripheral nerves with US remains controversial. To the best of our knowledge, there is still no in vivo neural recording study that has applied US stimulation to a nerve isolated from surrounding tissue to confirm direct activation effects. Here, we show that US cannot excite an isolated mammalian sciatic nerve in an in vivo preparation, even at high pressures (relative to levels recommended in the FDA guidance for diagnostic ultrasound) and for a wide range of parameters, including different pulse patterns and center frequencies. US can, however, reliably inhibit nerve activity whereby greater suppression is correlated with increases in nerve temperature. By prohibiting the nerve temperature from increasing during US application, we did not observe suppressive effects. Overall, these findings demonstrate that US can reliably inhibit nerve activity through a thermal mechanism that has potential for various health disorders, though future studies are needed to evaluate the long-term safety of therapeutic ultrasound applications.

Abstract via europepmc.

Flags from extraction

• exposures[*].timing.pulse_duration_ms — Pulse-duration/duty-cycle/PRF/TD ranges are stated once in Methods as the general parameter space tested with each of the three transducers (per Fig. 2 caption); the paper does not confirm the full sweep was completed identically at all three frequencies, only that 'these parameters (B, C, and E) were tested across ten animals.'
• exposures[*].free_field.pressure_kpa — A second, distinct pressure range specific to the nerve-modulation (EU-paired) experiments is also given per transducer (max 1.62/1.17/2.7 MPa, min 0.03/0.05/0.16 MPa for 0.22/0.52/1 MHz) that differs from the broader excitation-testing range recorded here; both ranges are described in protocol_description.
• exposures[*].free_field.isppa_w_cm2 — Aggregate maximum intensities are reported in the Discussion (ISPTA up to 62.48 W/cm2, ISPPA up to 833 W/cm2) but are not clearly attributed to a single specific transducer/frequency, so left not_reported per exposure rather than assigned to one frequency.
• n_subjects — Total of 41 guinea pigs used across the whole study; individual sub-experiments (e.g., 'five animals' for the parameter-response map, 'three animals' for thermal controls) used smaller, overlapping subsets not separately itemised here.