GCaMP fiber photometry reveals mechanistic insights into focused ultrasound neuromodulation in acute seizures
Chen-Syuan Huang, Yi-Chun Yeh, Po-Chun Chu, Yi-Tse Hsiao, Hsiang-Yu Yu, Robert S. Fisher, Hao-Li Liu
npj Acoustics 2026 · 10.1038/s44384-026-00057-6
Abstract
Generalized seizures represent a major clinical challenge in epilepsy, often resistant to pharmacological treatment and associated with significant morbidity. While low-intensity focused ultrasound (FUS) has emerged as a promising noninvasive neuromodulation strategy to suppress epileptiform activity, the underlying calcium mechanism remains poorly understood. This study, utilizing simultaneous hippocampal GCaMP fiber photometry and electrocorticography (ECoG) in acute pentylenetetrazol-induced seizure mouse models, investigated whether FUS stimulation could modulate intracellular calcium dynamics and network excitability. FUS was applied to the hippocampus with a mechanical index of 0.2, a duty cycle of 7.5%, and a total duration of 10 min. Our findings demonstrated a strong correlation between epileptic calcium transients and ECoG spikes, and FUS significantly attenuated both modalities for up to 40 min. Immunofluorescence analyses in the dentate gyrus revealed decreased c-Fos expression co-localized with both NMDAR2B and GAD65/67 after FUS treatment, indicating an overall reduction in both excitatory and inhibitory synaptic transmission. These results suggest that low-intensity FUS exerts calcium-dependent anti-seizure effects by modulating the excitatory-inhibitory balance. By providing real-time insights into neural network excitability, GCaMP fiber photometry complements traditional electrophysiology and serves as a potent mechanistic surrogate for assessing therapeutic efficacy, potentially guiding future closed-loop neuromodulation strategies.
Abstract via europepmc.
Exposures
Exposure 1: Transcranial FUS to hippocampus (PTZ + FUS group)
Target: dentate gyrus — “hippocampus (dentate gyrus, DG); acoustic beam also traversed overlying cerebral cortex”
Device: custom-built
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,000 | ✓✓✓ |
| Pulse duration (ms) | 0.75 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 100 | ✓✓✓ |
| Duty cycle (%) | 7.5pulse duration × PRF gives 7.5% | ✓✓✓ |
| Sonication duration (s) | 600 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | 200 | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | 1.62 | ✓✓✓ |
| In-situ Ispta (W/cm²) | 0.16 | ✓✓✓ |
FUS sonication was applied using a pulse repetition frequency of 100 Hz, pulse duration of 0.75 ms, DC of 7.5%, and a total stimulation duration of 10 min. Sonication was synchronized with the start of the second recording epoch (immediately after PTZ injection). Neural activity was recorded across four phases: a 15-min baseline (Pre), 10 min after PTZ (PTZ), 10 min during FUS stimulation (FUS), and a subsequent 40-min post-stimulation phase (Post).
Flags from extraction
n_subjects— Paper reports two separate cohorts exposed to FUS: the in vivo PTZ+FUS group (n=10, for GCaMP/ECoG) and the ex vivo PTZ+FUS subgroup used for immunofluorescence (n=7, inferred from n=5 Normal + n=6 PTZ-alone + n=7 FUS hemisphere = 18 total ex vivo). No single combined total is stated, so both group sizes are listed.exposures[0].in_situ.pressure_kpa— Value of 0.2 MPa is explicitly described as derated for 20% skull attenuation, so it is recorded as in_situ (method=derating) rather than free_field; no separate free-field (pre-attenuation) pressure value is stated in the text.sham_type— No sham ultrasound device/arm is described; comparator groups (Normal, PTZ-alone) simply did not receive FUS, closest fit is no_treatment_control.