Manipulating neuronal activity in the mouse brain with ultrasound: A comparison with optogenetic activation of the cerebral cortex
Michele E. Moore, John M. Loft, William C. Clegern, Jonathan P. Wisor
Neuroscience Letters 2015, 604, 183-187 · 10.1016/j.neulet.2015.07.024
Abstract
Low-intensity focused ultrasound induces neuronal activation via mechanisms that remain to be elucidated. We recorded local field potential fluctuations in the motor cortex in response to ultrasound stimulation of the somatosensory barrel cortex, comparing them to those recorded in response to optogenetic stimulation of interneurons and pyramidal neurons of the somatosensory cortex in the same animals. Comparison of the waveform produced by ultrasound stimulation to those produced by optogenetic stimulation revealed similarities between ultrasound-induced responses and optogenetically-induced responses to pyramidal cell stimulation, but not interneuron stimulation, which may indicate that ultrasound stimulation is mediated by excitation of cerebral cortical pyramidal neurons. Comparison of post mortem evoked responses to responses in living tissue confirmed the necessity for excitable tissue in the evoked response. Collectively, these experiments demonstrate an excitation-dependent response to low-frequency transdural ultrasound stimulation of cerebral cortical neuronal activity.
Abstract via europepmc.
Exposures
Exposure 1: Ultrasound stimulation of somatosensory barrel cortex
Target: primary somatosensory cortex — “somatosensory barrel cortex”
Device: Ultran · Ultran Group · GS350-D19 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 350 | ✓✓✓ |
| Pulse duration (ms) | 0.214 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2,000 | ✓✓✓ |
| Duty cycle (%) | 42.8pulse duration × PRF gives 42.8% | ✓✓✓ |
| Sonication duration (s) | 0.01 | ✓✓✓ |
| 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 |
A TTL trigger triggered waveform generator 1 to undergo a square wave train of 10 ms duration (the ultrasound stimulus train). During each 10 ms stimulus train, waveform generator 1 produced twenty square pulsed waves (each of 0.5 ms duration) with a 50% duty cycle (2.0 kHz repetition), and at the onset of each of these 20 pulses waveform generator 2 triggered the transducer to emit 75 acoustic cycles at 350 kHz (~0.214 ms per ultrasound event). Stimulation events (10 ms stimulus trains) were delivered at 7 Hz throughout the duration of the ten-minute recordings; craniotomy-based transdural stimulation was delivered to the somatosensory barrel cortex with LFP recorded in monosynaptically-connected motor cortex.
Flags from extraction
n_subjects— Experiment 1 (n=14: 4 Thy1-ChR2 + 5 nNOS-ChR2 + 5 non-ChR2) and Experiment 2 (a separate cohort of 8 Thy1-ChR2 mice) are distinct cohorts; totals are listed rather than summed.exposures[0].unspecified_domain.isppa_w_cm2— Acoustic intensity was explicitly not measured in this study; the 0.07-0.23 W/cm2 figure is a citation of a prior study's reported value for the same transducer/configuration ('acoustic intensity...is reported as...'), not a measurement made here. Midpoint of the cited range recorded; domain (free field vs in situ) not specified.