Designing and Pilot Testing a Novel Transcranial Temporal Interference Stimulation Device for Neuromodulation.

Transcranial temporal interference stimulation (tTIS) has been proposed as a new neuromodulation technology for non-invasive deep-brain stimulation (DBS). However, few studies have detailed the design method of a tTIS device and provided system validation. Thus, a detailed design and validation scheme of a novel tTIS device for animal brain stimulation are presented in this study. In the proposed tTIS device, a direct digital synthesizer (DDS) was used to generate a sine wave potential of different frequencies, which was converted to an adjustable sine wave current. A current transformer was used to produce electrical isolation of different channels, which eliminated the current crosstalk between channels and greatly increased the load capacity by amplifying the output voltage. Several in vitro experiments were first conducted to validate the tTIS device. Our results indicated that the error percentages of the stimulation currents were within ±2%. Current crosstalk between channels was almost completely eliminated. Then, in vivo electric field measurement shows that the 2-pole arrangement may provide better cortical targeting than the 4-pole mode. A pilot animal experiment was conducted in which evoked motion and electromyographic activation of the contralateral forelimb were observed, which indicated that the 2-pole tTIS had successfully activated the primary motor cortex in a rat. Motor activation induced by the 2-pole tTIS demonstrated the feasibility and safety potential when applying our tTIS device for neuromodulation.