Guidelines for successful motor cortex ultrasonic neurostimulation in mice
Rasha Noureddine, Alexandre Surget, Tarik Iazourene, Marie Audebrand, Hoda Eliwa, Bruno Brizard, Mohamad Nassereddine, Yassine Mofid, Jamal Charara, Ayache Bouakaz
Ultrasonics 2023 · 10.1016/j.ultras.2022.106888
Abstract
Background Ultrasound neurostimulation (USNS) is a non-invasive neuromodulation technique that might hold promise for treating neuropsychiatric disorders with regards to its noninvasiveness, penetration depth, and high resolution. Objective We sought in this experimental study to provide detailed and optimized protocol and methodology for a successful ultrasonic neurostimulation of the Primary Motor Cortex (M1) in mice addressed to young researchers/students beginning their research in the field of ultrasonic neurostimulation and encountering practical challenges. Methods A 500 kHz single-element transducer was used for stimulating the primary motor cortex at different acoustic pressures in C57BL/6 mice at various anesthesia levels. To further illustrate the effect of anesthesia, real time visual observations of motor responses validated with video recordings as well as electromyography were employed for evaluating the success and reliability of the stimulations. Results Detailed experimental procedure for a successful stimulations including targeting and anesthesia is presented. Our study demonstrates that we can achieve high stimulation success rates (91 % to 100 %) at acoustic pressures ranging from 330 kPa to 550 kPa at anesthesia washout period. Conclusions This study shows a reliable and detailed methodology for successful USNS in mice addressed to beginners in ultrasonic brain stimulation topic. We showed an effective USNS protocol. We offered a simple and consistent non-invasive technique for locating and targeting brain zones. Moreover, we illustrated the acoustic pressure and stimulation success relationship and focused on the effect of anesthesia level for successful stimulation.
Abstract via europepmc.
Exposures
Exposure 1: 500 kHz stimulation of left M1 in mice at 55-550 kPa
Target: primary motor cortex — “left primary motor cortex (M1) of the forelimbs”
Device: IGT / Imasonic · Imasonic, Besançon, France · single-element transducer, 500 kHz, 57.5 mm focal length, 41 mm active diameter
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | not applicable | ⚑ |
| Sonication duration (s) | 0.16 | ✓✓✓⚑ |
| 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) | 55, 550swept | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | 0.155 | ✓✓✓ |
A single pulse of 80,000 cycles (pulse duration 160 ms) repeated every 10 s (PRF = 0.1 Hz); 3 pulses per pressure step in the anaesthesia experiment and 10 pulses 10 s apart per step in the pressure experiment. Table 1 lists the stimulation duration as 10 minutes.
Flags from extraction
exposures[0].in_situ.pressure_kpa— Peak negative pressure was measured behind an ex vivo mouse skull in a water tank and adjusted for 12 % skull attenuation; recorded as a measurement through skull. Range is a sweep (220-440 kPa in the anaesthesia experiment).exposures[0].unspecified_domain.ispta_w_cm2— Ispta 155 mW/cm2 is given only for the maximum 550 kPa; domain not stated.exposures[0].timing.sonication_duration_s— Each trial is one 160 ms burst; paper states PRF 0.1 Hz and 'pulse duration 160 ms' (burst per trial treated as continuous per the schema rule, PRF kept in the description).n_subjects— 3 mice in the anaesthesia experiment and 10 mice in the pressure experiment; unclear whether the 3 are a subset of the 10. Quote supports the 10.exposures[0].timing.duty_cycle_pct— Not stated; pulse every 10 s.