A piezoelectric micromachined ultrasound transducer combined with recording electrodes for acute brain preparations in vitro
Ryo Furukawa, Takahiro Yoshikawa, Shuichi Murakami, Takashi Tateno
Journal of Neuroscience Methods 2024, 403, 110048 · 10.1016/j.jneumeth.2023.110048
Abstract
Background Ultrasound stimulation is used to noninvasively stimulate the local and deep areas of the brain. However, the detailed cellular mechanisms of neural activation are still unclear because studies on micro-stimulation at the cellular level are lacking. New method To modulate neural activity at the cellular level, we developed a piezoelectric micromachined ultrasound transducer (PMUT), having circular diaphragms for application on acute brain slice preparations. To monitor neural activities, additionally, we fabricated recording microelectrodes onto the same PMUT device for closed-loop application. Results To examine the PMUT-driven cellular responses of a brain slice, intracellular calcium signals in individual cells were measured using two calcium indicators. We successfully observed the intracellular responses triggered by the ultrasound of our novel PMUT. In addition, we performed recordings of local field potentials in a brain slice, demonstrating its usefulness as a simultaneous recording interface. Comparison with existing method(s) Conventional ultrasound stimulators are open-loop systems that risk inducing excessive neural activity because of the absence of neural activity monitoring. In contrast, our PMUT is packaged in a single device with both stimulation and sensor interface for neuromodulation. Further, there are no published reports on in vitro microdevices that can be used for ultrasound stimulation in rodent cortical slices that are several hundred micrometers thick, which maintain the cortical laminar structure and intrinsic neural networks. Conclusions Our findings suggest that this novel PMUT device has the potential for being a powerful tool for in vitro brain slice applications and effective closed loop ultrasound stimulation.
Abstract via europepmc.
Exposures
Exposure 1: Ultrasound stimulation of auditory cortex brain slice
Target: auditory cortex — “auditory cortex (brain slice)”
Device: custom-built · PMUT (custom piezoelectric micromachined ultrasound transducer)
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 880 | ✓✓✓ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | 100 | ✓? |
| Sonication duration (s) | 1 | ✓✓✓ |
| Free-field pressure (kPa) | 65.6 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not applicable | |
| In-situ pressure (kPa) | not applicable | |
| In-situ Isppa (W/cm²) | not applicable | |
| In-situ Ispta (W/cm²) | not applicable |
We applied ultrasound stimulation (880 kHz continuous wave) for 1 s, and imaged the Ca2+ transients, followed by monitoring of Ca2+ transients during the recovery period for 1 s (total of 3 s per trial). Each measurement consisted of 10 trials with the same stimulation conditions; sham stimulation used 0-V input voltage; a 5 min rest period was inserted between repeated stimulations.
Flags from extraction
n_subjects— Paper states four mice but gives a sex breakdown of two males and five females, which sums to seven, not four; likely a typo.exposures[0].target.terms— Paper states slices were cut to contain the auditory cortex but does not confirm stimulation/imaging was confined to that region; other cortical cell types may have been included.