Ultrasound Stimulation of Periaqueductal Gray Induces Defensive Behaviors
Yibo Wang, Lili Niu, Wen Meng, Zhengrong Lin, Junjie Zou, Tianyuan Bian, Xiaowei Huang, Hui Zhou, Long Meng, Ping Xie, Hairong Zheng
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2021 · 10.1109/tuffc.2020.2975001
Abstract
Low-intensity focused ultrasound stimulation (LIFUS) has the potential to noninvasively penetrate the intact skull and to modulate neural activity in the cortex and deep brain nuclei. The midbrain periaqueductal gray (PAG) is associated with the generation of defensive behaviors. The aim of this study was to examine whether LIFUS of the PAG induced defensive behaviors in mice. A 3.8-MHz head-mounted ultrasound transducer with a small focus size (0.5 mm × 0.5 mm) was fabricated in house to precisely stimulate the free-moving mice. The corresponding behaviors were recorded in real time. Avoidance, flight, and freezing were used to assess ultrasound-induced defensive responses. The safety of LIFUS was examined via hematoxylin and eosin (H&E) staining and Nissl staining. Ultrasound stimulation of the PAG induced multiple defensive behaviors, including location-specific passive avoidance behavior, flight, and freezing. In addition, H&E and Nissl staining verified that LIFUS did not cause any injury to the brain tissue. These findings demonstrate that LIFUS may have neuromodulatory effects on the innate defensive behaviors in mice. LIFUS may be used as a novel neuromodulatory tool for the treatment of psychological diseases associated with defensive behaviors.
Abstract via europepmc.
Exposures
Exposure 1: LIFUS of PAG, head-mounted 3.8 MHz transducer
Target: periaqueductal gray — “periaqueductal gray (PAG)”
Device: custom-built · in-house (Shenzhen Institutes of Advanced Technology) ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 3,800 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓⚑ |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓ |
| Duty cycle (%) | 50pulse duration × PRF gives 50% | ✓✓✓ |
| Sonication duration (s) | not reported | ⚑ |
| Free-field pressure (kPa) | 136 | ✓✓✓⚑ |
|---|---|---|
| Free-field Isppa (W/cm²) | 0.642 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 0.321 | ✓✓✓ |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 63.4 | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | 0.14 | ✓✓✓ |
| In-situ Ispta (W/cm²) | 0.07 | ✓✓✓ |
TBD 0.5 ms, PRF 1000 Hz, DC 50%; ultrasound delivered into the PAG each time the mouse crossed to the stimulation side (rtPPT), continuously over a 20-min open field session, and in 1-min OFF / 1-min ON cycles in the rat exposure test (three cycles). NTB and ISI are set on the function generator but values are not given in the text.
Flags from extraction
exposures[0].in_situ.pressure_kpa— Through-skull values were measured with a hydrophone in a water tank with an excised mouse skull in the path; treated as in_situ by measurement through skull, not measured in brainexposures[0].free_field.pressure_kpa— Pressure given as peak negative pressure; intensities converted from mW/cm2 to W/cm2exposures[0].timing.sonication_duration_s— Stimulus train/burst duration not stated; protocol varies by assay and ISI/NTB values not in textexposures[0].timing.pulse_duration_ms— Pulse duration from the Fig. 1 legend (TBD = 0.5 ms), consistent with PRF 1000 Hz and DC 50%n_subjects— Group sizes only: rtPPT n=7, OFT sham 13 and LIFUS 14, RET n=15, histology 12 mice; overlap between assays unclear so no total givenreadouts— The paper's abstract states the transducer was held in place during behavioural tests in awake free-moving mice