Ultrasonic neuromodulation by brain stimulation with transcranial ultrasound
Yusuf Tufail, Anna Yoshihiro, Sandipan Pati, Monica M Li, William J Tyler
Nature Protocols 2011, 6, 1453-1470 · 10.1038/nprot.2011.371
Abstract
Brain stimulation methods are indispensable to the study of brain function. They have also proven effective for treating some neurological disorders. Historically used for medical imaging, ultrasound (US) has recently been shown to be capable of noninvasively stimulating brain activity. Here we provide a general protocol for the stimulation of intact mouse brain circuits using transcranial US, and, using a traditional mouse model of epilepsy, we describe how to use transcranial US to disrupt electrographic seizure activity. The advantages of US for brain stimulation are that it does not necessitate surgery or genetic alteration, but it confers spatial resolutions superior to other noninvasive methods such as transcranial magnetic stimulation. With a basic working knowledge of electrophysiology, and after an initial setup, ultrasonic neuromodulation (UNMOD) can be implemented in less than 1 h. Using the general protocol that we describe, UNMOD can be readily adapted to support a broad range of studies on brain circuit function and dysfunction.
Abstract via europepmc.
Exposures
Exposure 1: Pulsed transcranial ultrasound (TPU) stimulation of motor cortex
Target: motor cortex — “motor cortex”
Device: Ultran · Ultran · GS 350-D19 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 350 | ✓✓✓ |
| Pulse duration (ms) | 0.214 | ✓✓✓⚑ |
| Pulse repetition frequency (Hz) | 2,000 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 42.8% | |
| 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 |
The corresponding parameters for this waveform are A = 0.35 MHz, c.p.p. = 75, np = 200 and PRF = 2.0 kHz; each 5-Vpp square wave from FG1 triggers a 1-Vpp sine-wave pulse of 75 cycles at 0.35 MHz from FG2, repeated at a PRF of 2 kHz until 200 pulses (np) have been produced. Typical parameter ranges for pulsed UNMOD stimuli span Af 0.25-0.50 MHz, c.p.p. 50-490, PRF 1-3 kHz and np 250-1,000.
Exposure 2: Continuous-wave (CW) ultrasound applied to intact brain for seizure induction/attenuation
Target: whole brain or unfocused — “intact mouse brain”
Device: Ultran · Ultran · GS 350-D19 ✓
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 350 | ✓✓✓ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | 100 | ✓?⚑ |
| Sonication duration (s) | 5 | ✓✓✓ |
| 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 |
US stimuli delivered in CW-mode for 5 s to normal mice can induce seizure activity lasting more than 20 s and can disrupt chemically induced electrographic seizure activity in epileptic animals; FG2 can alternatively be set to generate CW waveforms via sustained TTL inputs lasting 1 to 10 s, and pulsed UNMOD stimuli can instead be delivered to the brain once every 0.5 to 2 s to disrupt ongoing seizure activity.
Flags from extraction
exposures[0].timing.pulse_duration_ms— Computed from stated cycles-per-pulse (75) and frequency (0.35 MHz) per the pulse-duration synonym rule (75/350 kHz = 0.214 ms); not stated as a duration value directly.exposures[0]— Figure 3 legend states '80 c.p.p.' for a waveform otherwise identical (0.35 MHz, 200 np, 2.0 kHz PRF), whereas the main procedure text (Steps 7-14 and the accompanying Critical Step) specifies 75 c.p.p.; the main-text value (75) was used and the figure legend was not used to establish the number, per the figures-do-not-count rule.exposures[0].timing.sonication_duration_s— Not computed from np/PRF (200/2000 s = 0.1 s) per the instruction not to derive one timing number from the others; left not_reported.exposures[1].timing.duty_cycle_pct— 100% is the categorical entailment of the paper's own 'continuous wave (CW)' label, not a percentage stated numerically in the text.adverse_events— The paper's safety statements (e.g. 'US has been found effective for acutely stimulating brain circuits without producing damage...') cite prior studies (refs 4,5), not new data generated by this protocol paper; recorded as not_reported rather than attributing those findings to this record.exposures[1].target— The epilepsy (CW) protocol is described as coupling the transducer directly to the head without mention of a collimator, unlike the motor-cortex protocol; classified as whole_brain_or_unfocused, but the paper does not explicitly rule out the same motor-cortex placement being used.sham_type— This is a methods/protocol paper; no sham or control condition is described for either the motor-cortex stimulation or the epilepsy-attenuation procedures.direction_of_effect— Coded bidirectional because the paper reports both excitatory effects (evoked motor/hippocampal activity, CW-induced seizure activity) and an inhibitory/therapeutic use (CW or pulsed US attenuating ongoing seizures), depending on waveform and context.