Region-specific effects of ultrasound on individual neurons in the awake mammalian brain
Hua-an Tseng, Jack Sherman, Emma Bortz, Ali Mohammed, Howard J. Gritton, Seth Bensussen, Rockwell P. Tang, Dana Zemel, Thomas Szabo, Xue Han
iScience 2021, 24, 102955 · 10.1016/j.isci.2021.102955
Abstract
Ultrasound modulates brain activity. However, it remains unclear how ultrasound affects individual neurons in the brain, where neural circuit architecture is intact and different brain regions exhibit distinct tissue properties. Using a high-resolution calcium imaging technique, we characterized the effect of ultrasound stimulation on thousands of individual neurons in the hippocampus and the motor cortex of awake mice. We found that brief 100-ms-long ultrasound pulses increase intracellular calcium in a large fraction of individual neurons in both brain regions. Ultrasound-evoked calcium response in hippocampal neurons exhibits a rapid onset with a latency shorter than 50 ms. The evoked response in the hippocampus is shorter in duration and smaller in magnitude than that in the motor cortex. These results demonstrate that noninvasive ultrasound stimulation transiently increases intracellular calcium in individual neurons in awake mice, and the evoked response profiles are brain region specific.
Abstract via europepmc.
Exposures
Exposure 1: Ultrasound stimulation of hippocampal CA1 during calcium imaging in awake mice
Target: CA1 — “hippocampus CA1”
Device: other named manufacturer · The Ultra Group Inc · GS350-D13 (planar ultrasound transducer) ✓
| 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) | 0.1 | ✓✓✓ |
| Free-field pressure (kPa) | 440 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationsingle value | |
| In-situ pressure (kPa) | 24.3 | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
During each imaging session, mice experienced 20 trials of ultrasound stimulation, each trial lasting 30 or 60 s, with ultrasound onset 10 s after start of imaging. Each stimulation consisted of 200 pulses at 2 kHz, each pulse containing 75 cycles of 350 kHz sine wave ultrasound, for a total 100-ms-long stimulation period, delivered via a planar transducer placed under the animal's head.
Exposure 2: Ultrasound stimulation of motor cortex during calcium imaging in awake mice
Target: motor cortex — “motor cortex”
Device: other named manufacturer · The Ultra Group Inc · GS350-D13 (planar ultrasound transducer) ✓
| 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) | 0.1 | ✓✓✓ |
| Free-field pressure (kPa) | 440 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationsingle value | |
| In-situ pressure (kPa) | 26.3 | ✓✓✓ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Following the same protocol as the hippocampal experiments, mice experienced 20 trials of 30 or 60 s each, with ultrasound onset 10 s after imaging start. Each stimulation consisted of 200 pulses at 2 kHz, each pulse containing 75 cycles of 350 kHz sine wave ultrasound, for a total 100-ms-long stimulation period, delivered via a planar transducer placed under the animal's head; an off-target control positioned the transducer under the abdomen instead.
Flags from extraction
exposures[*].timing.pulse_duration_ms— Computed as cycles-per-pulse divided by fundamental frequency (75 cycles / 350 kHz = 0.214 ms), which the extraction instructions list as an allowed unit conversion rather than prohibited arithmetic.n_subjects— Paper never gives one aggregate subject count; reported group sizes for the two brain-region ultrasound exposures are given as a list (14 mice for hippocampus, 4 mice for motor cortex). Separate sham (3 mice) and off-target abdomen-control (5 mice) groups are not included since they did not receive on-target ultrasound.exposures[0].in_situ.pressure_kpa— Exact number (24.3 kPa) appears in the source text but the sentence is split awkwardly across a figure-caption insertion in the extracted markdown; quoted the sentence fragment containing the number as it appears verbatim.