Authors :
Presenting Author: Ryohei Yoshimoto, MS – Emory University
Emma Acerbo, PhD – Emory University
Thomas Eggers, PhD – Emory University
Matthew Stern, PhD – Emory University
Nealen Laxpati, MD, PhD – Emory University School of Medicine
Ken Berglund, PhD – Emory University
Claire-Anne Gutenkust, PhD – Emory University
Rationale:
Deep brain stimulation is an established and effective therapy for epilepsy and other neurological disorders. However, its invasive surgical procedure involves inherent risks. Temporal Interference (TI) electrical stimulation is a recently proposed noninvasive technique for modulating deep brain regions. It delivers two high-frequency electrical currents with a slight frequency difference. At the site of interference, the difference between the two high frequencies creates an amplitude modulation that can stimulate neurons. Although TI has shown promise in enabling deep brain modulation, the precise spatiotemporal characteristics of neuronal responses remain poorly understood. In this study, we aimed to investigate the fundamental neuronal response characteristics of TI stimulation using an in vitro brain slice model.
Methods:
We used albino mice that had received at birth intracerebroventricular injection of a viral vector that expressed a calcium indicator protein, GCaMP8s, in neurons. Acute brain slices were prepared when the animals reached 4–8 weeks old. TI stimulation was applied through two pairs of tungsten electrodes in the bath.
Experiment 1: To examine the amplitude modulation properties of TI stimulation, electric fields were monitored using a multi-electrode array (MEA), and neuronal activity was assessed by calcium imaging with two-photon microscopy.
Experiment 2: To further investigate neuronal responses with higher temporal resolution, single-unit recordings were obtained using the MEA during TI stimulation.
Results:
Experiment 1: MEA recordings confirmed amplitude modulation of TI stimulation. Two-photon calcium imaging revealed that neuronal activation in the target region was phase-locked to the envelope frequency, whereas neurons in off-target regions did not show a response that followed the envelope frequency.
Experiment 2: Single-unit recordings demonstrated that individual neurons exhibited spiking responses entrained to the envelope frequency of TI stimulation.
Conclusions:
These findings demonstrate that TI stimulation can selectively activate neurons in targeted regions with the envelope frequency. The phase-locked calcium responses and entrained single-unit spiking support the ability of TI to drive neuronal activity with spatial specificity and temporal precision. Together, these results highlight the potential of TI stimulation as a promising strategy for noninvasive deep brain neuromodulation and provide a foundation for its future application in epilepsy treatment.
Funding:
This work was supported by the NIH BRAIN Initiative grant “Advancing Non-Invasive Brain Stimulation: A Comprehensive Study of Temporal Interference Mechanisms (CNS-STIM), Project Number 5R01NS138733-02