Patch clamp recordings of action potentials from pyramidal neuron in hippocampus CA1 under focused ultrasound neurostimulation with MEMS self-focusing acoustic transducer

Abstract

Objective. This study aims to investigate the modulatory effects of focused ultrasound (FUS) on neuronal activity at the single-cell level, using whole-cell patch clamp recordings in hippocampal slices. Approach. A self-focused acoustic transducer (SFAT) was designed and fabricated on a 127 µ m-thick translucent lead zirconate titanate substrate to allow infrared light transmission for visualizing neurons during patch clamp experiments. The SFAT operates at 18.4 MHz, producing low-intensity FUS with a 46 µ m focal diameter at a depth of 400 µ m. Three types of SFAT-active, FUS-blocking control, and low-electromagnetic interference (EMI) versions-were developed to assess the effects of acoustic stimulation, thermal heating, and EMI. Neuronal responses were recorded across 78 tissue samples from 29 animals using 48 combinations of acoustic parameters, including peak-to-peak voltage, pulse repetition frequency (PRF), and pulse duration. Main results. Whole-cell patch clamp recordings from CA1 pyramidal neurons in rat hippocampal slices revealed that FUS induces both inhibitory and excitatory effects on action potential firing, depending on the stimulation parameters. Inhibition was found to be the dominant response, while excitation was mainly attributable to thermal effects. Optimal inhibition was achieved with 60 Vpp (ISAPA = 2.11 W cm -2 ), 35 kCycles/pulse (1.90 ms), and 100 Hz PRF, yielding a 60% success rate. Conversely, excitation was observed in 60% of trials using 120 Vpp (ISAPA = 8.44 W cm -2 ), 50 kCycles/pulse (2.72 ms), and 20 Hz PRF. Significance. This work presents a novel neuromodulation platform that combines high-frequency focused ultrasound with real-time whole-cell patch clamp recording at single-neuron resolution. The results provide direct electrophysiological evidence of parameter-dependent, bidirectional modulation of neuronal activity by FUS, offering new insights into its underlying mechanisms and helping define stimulation protocols for future neurotherapeutic applications.

Abstract via europepmc.

Flags from extraction

• exposures[0].free_field.isppa_w_cm2 — Intensities are spatial-average pulse-average (ISAPA), not spatial-peak, because the hydrophone was larger than the focus. Text gives 0.44, 2.11, 8.44 W/cm2 for 40, 60, 120 Vpp but Table 2 gives 0.94 W/cm2 for 40 Vpp; recorded the text list. Measurements made on a longer-focal-length SFAT in a water tank.
• exposures[0].free_field.pressure_kpa — Only the 40 Vpp pressure (0.16 MPa) is stated in text; Table 2 has a column headed ISAPA (kPa) listing 160, 262, 524 for 40, 60, 120 Vpp. Value recorded is for the lowest voltage only.
• exposures[0].free_field.ispta_w_cm2 — ISATA (spatial-average time-average) range of 1 to 1031 mW/cm2 over all parameter sets, called ISPTA in this sentence.
• exposures[0].timing.duty_cycle_pct — Duty cycles are given per row in Table 2 (0.54 to 50.80 percent across sweeps); no single quotable range, so left not_reported.
• exposures[0].timing.pulse_duration_ms — Pulse durations stated for 5k to 65k cycles per pulse (0.27 to 3.53 ms); table cycle counts range up to 65 000.
• exposures[0].timing.pulse_repetition_frequency_hz — Text says 1-200 Hz; Table 2 lists 5-200 Hz at some voltages.
• exposures[0].timing.sonication_duration_s — 30 s of FUS followed by a 2 min rest; up to 15 stimuli per cell.
• n_subjects — 29 animals, 78 slices, 323 experimental events; 22 animals for active devices and 7 for FUS-blocking control.
• direction_of_effect — Both inhibition (30%) and excitation (15%) observed; excitation likely thermal (similar rate in the FUS-blocking control).