Focused ultrasound suppresses pentylenetetrazol-induced epileptiform activity in rats and alters connectivity measured by functional MRI

Po-Chun Chu, Wei-Hong Ruan, Chen-Syuan Huang, Yi-Jing Juan, Jyh-Horng Chen, Hsiang-Yu Yu, Robert S. Fisher, Hao-Li Liu

Scientific Reports 2025, 15 · 10.1038/s41598-025-15305-0

rodentepilepsyeeg megfmrihistology molecular

Abstract

Focused ultrasound (FUS) has emerged as a promising neuromodulation technique for reducing regional brain excitability, offering a potential therapeutic approach for drug-resistant epilepsy (DRE). However, its underlying mechanisms remain unclear, particularly regarding functional connectivity alterations in seizure-related brain networks. This study investigates the relationship between FUS-induced seizure suppression and brain functional connectivity using EEG and resting-state fMRI (rs-fMRI). Using a pentylenetetrazol (PTZ)-induced epilepsy rat model (n = 28), we applied burst-mode FUS with 0.25 MI, I SPTA = 0.3 W/cm 2 with low (30s-on-90s-off)/high (90s-on-30s-off) doses with 10-minute sonication durations to the anterior nucleus of the thalamus (ANT), resulting in approximately 36% reduction in hippocampal spike activity. Rs-fMRI analysis (36 × 36 connectivity matrix) revealed that the PTZ-induced seizure reduction strongly correlates with significant whole-brain connectivity changes, including a 45.1% decrease in connectivity between the anterior thalamic and hippocampal networks. Histological analysis confirmed that FUS preferentially modulates key brain regions involved in epileptic circuits, particularly the thalamus and hippocampus. These findings provide compelling evidence that FUS selectively alters seizure-related functional networks, highlighting its potential as a noninvasive therapeutic approach for epilepsy.

Abstract via europepmc.

Speciesrat (Sprague-Dawley)

Subjectsnot reported animals

Sessions per subject1

Randomisednot reported

Blindingnot reported

Sham / controlnone

Auditory controlnot reported

Readout timingoffline

Anaesthesiaanaesthetised

Readoutseeg meg, fmri, histology molecular — Hippocampal EEG spike counting (delta/theta/alpha/gamma bands); resting-state fMRI 36x36 ROI functional connectivity matrix; c-Fos immunohistochemistry; H&E histology

Direction of effectinhibitoryFUS to the ANT reduced PTZ-induced hippocampal EEG spike counts by ~29-42% (low- and high-dose pooled, ~36% overall) and reduced thalamus-hippocampus resting-state functional connectivity (45.1% decrease), normalizing PTZ-induced increases in c-Fos expression in the thalamus-hippocampus circuit.

Adverse eventsnone observedH&E histology showed no obvious tissue disruption, immune cell infiltration, or microglial activation in cortex, thalamus or hippocampus of FUS-treated animals, indicating FUS did not cause detectable histological damage.

Exposures

Exposure 1: Burst-mode FUS to anterior nucleus of thalamus (low-dose and high-dose ISI protocols)

Target: anterior thalamic nucleus — “anterior nucleus of the thalamus (ANT)”
Device: custom-built

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	1,000	✓✓✓
Pulse duration (ms)	not reported
Pulse repetition frequency (Hz)	not reported	⚑
Duty cycle (%)	30	✓✓✓
Sonication duration (s)	30, 90swept	✓✓✓

Pressure and intensity, by domain
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)	not reported
In-situ Isppa (W/cm²)	not reported
In-situ Ispta (W/cm²)	not reported	⚑
Ispta, domain unspecified (W/cm²)	0.3	✓✓✓

Protocol, in the paper’s words

Burst-mode FUS (0.25 MI, 30% duty cycle) was delivered for a total exposure duration of 600 s (10 min) as 5 on/off cycles: a 'high-dose' protocol of 90-s on periods with 30-s inter-stimulus interval (ISI), and a 'low-dose' protocol of 30-s on periods with 90-s ISI. EEG was recorded 40 min after the end of FUS; spike counts decreased similarly (29-42%) for both dose protocols so they were pooled for connectivity analysis.

Flags from extraction

n_subjects — Paper gives group-level counts (32 total; 28 received PTZ; histology used Normal n=4, PTZ-alone n=4, PTZ-FUS n=8) but never states how many of the 28 PTZ animals were assigned to the PTZ-FUS (actual FUS-exposed) group for the main EEG/fMRI experiments, so left not_reported.
exposures[0].in_situ.ispta_w_cm2 — Abstract and the 'FUS sonication protocol' Results section both state ISPTA = 0.3 W/cm2, but the Methods 'FUS setup and parameters design' section states the same 30% duty cycle 'was equivalent to FUS exposure intensities...of 0.7 W/cm2'; recorded the majority value (0.3) and flag this internal discrepancy.
exposures[0].timing.pulse_repetition_frequency_hz — Paper states MI (0.25) and duty cycle (30%) for the burst-mode FUS but never states a pulse repetition frequency or pulse duration, so both left not_reported (burst rule could not be resolved).
sham_type — Comparator groups (Normal, PTZ-alone) received no ultrasound exposure at all rather than an inactive-transducer sham, so coded as none with this flag for clarity.