A novel phase-difference transcranial alternating current stimulation system enables precise dual-site...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Neurotechnology

Background:

• Precise modulation of large-scale brain networks requires advanced neuromodulation with frequency-locked stimulation and stable inter-regional phase control.
• Conventional transcranial alternating current stimulation (tACS) systems often lack robust dual-channel phase regulation and validation under realistic biological impedance conditions.

Purpose of the Study:

• To present and validate a novel phase-difference tACS system (PD-stim) for programmable, high-precision phase offsets between stimulation targets.
• To assess the biological impedance stability, waveform fidelity, amplitude stability, and phase-delivery accuracy of the PD-stim system.

Main Methods:

• Engineering and in vivo validation of the PD-stim system.
• Measurement of biological impedance in rat medial prefrontal cortex and hippocampus during stimulation.
• Benchmark comparisons with a clinically approved tACS device using standardized resistive loads and in vivo conditions.
• Simultaneous dual-channel oscilloscope recordings to assess waveform fidelity and phase accuracy across theta, beta, and gamma frequency bands.

Main Results:

• Stable, frequency-dependent biological impedance profiles were observed in rat brain regions during stimulation.
• PD-stim demonstrated comparable waveform fidelity and amplitude stability to a clinical tACS device under both resistive and in vivo conditions.
• PD-stim consistently achieved high phase-delivery accuracy with stable sinusoidal waveforms across multiple frequency bands (theta, beta, gamma) under diverse conditions.

Conclusions:

• The PD-stim system is a precise, stable, and biologically robust dual-site neuromodulation platform.
• This technology overcomes key technical limitations of existing tACS systems for phase-specific brain network modulation.
• The validated engineering framework supports future investigations into the mechanisms of phase-specific neuromodulation in distributed brain networks.