Entrainment of cerebellar Purkinje cell spiking activity using pulsed ultrasound stimulation
Ahmet S. Asan, Qi Kang, Ömer Oralkan, Mesut Sahin
Brain Stimulation 2021, 14, 598-606 · 10.1016/j.brs.2021.03.004
Abstract
Background Focused ultrasound (FUS) has excellent characteristics over other non-invasive stimulation methods in terms of spatial resolution and steering capability of the target. FUS has not been tested in the cerebellar cortex and cellular effects of FUS are not fully understood. Objective/hypothesis To investigate how the activity of cerebellar Purkinje cells (PCs) is modulated by FUS with varying pulse durations and pulse repetition frequencies. Methods A glass microelectrode was inserted into the cerebellar vermis lobule 6 from the dorsal side to extracellularly record single unit activity of the PCs in anesthetized rats. Ultrasonic stimulation (500 kHz) was applied through a coupling cone, filled with degassed water, from the posterior side to target the recording area with varying pulse durations and frequencies. Results Simple spike (SS) activity of PCs was entrained by the FUS pattern where the probability of spike occurrences peaked at around 1 ms following the onset of the stimulus regardless of its duration (0.5, 1, or 2 ms). The level of entrainment was stronger with shorter pulse durations at 50-Hz pulse repetition frequency (PRF), however, peri-event histograms spread wider and the peaks delayed slightly at 100-Hz PRF, suggesting involvement of a long-lasting inhibitory mechanism. There was no significant difference between the average firing rates in the baseline and stimulation periods. Conclusion FUS can entrain spiking activity of single cells on a spike-by-spike basis as demonstrated here in the rat cerebellar cortex. The observed modulation potentially results from the aggregate of excitatory and inhibitory effects of FUS on the entire cortical network rather than on the PCs alone.
Abstract via europepmc.
Exposures
Exposure 1: Cerebellar cortex sonication with varying pulse duration and PRF
Target: cerebellar cortex — “cerebellar vermis lobule 6 or 7”
Device: Olympus / Panametrics · Olympus Scientific Solutions Americas Inc. · V-301-SU ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | 0.5, 1, 2swept | ✓✓✓ |
| Pulse repetition frequency (Hz) | 50, 100swept | ✓✓✓ |
| Duty cycle (%) | not reported | ⚑ |
| Sonication duration (s) | 0.5 | ✓✓✓ |
| Free-field pressure (kPa) | 88, 438swept | ✓✓✓⚑ |
|---|---|---|
| Free-field Isppa (W/cm²) | 0.26, 6.4swept | ✓✓✓ |
| 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 |
Ten-second-long neural recordings were collected and each second of recording contained 500 ms of ultrasound stimulation followed by 500 ms of no-stimulation period. The PRF was set to either 50 Hz or 100 Hz to make it close to the spontaneous firing rates of PCs. The pulse duration was adjusted to 0.5, 1, or 2 ms in sequential trials.
Flags from extraction
exposures[0].free_field.pressure_kpa— Pressure/intensity range is from water-tank hydrophone calibration; paper states these should be considered upper bounds for the actual tissue exposure since exact PC location within the field was unknown, so free-field vs in-situ assignment is uncertain.exposures[0].timing.duty_cycle_pct— Duty cycle not directly stated; not computed from pulse duration and PRF per protocol.n_subjects— 18 Purkinje cells were recorded across 6 animals; n_subjects given as number of animals, not units.