Designing and Implementing a Novel Transcranial Electrostimulation System for Neuroplastic Applications: A Preliminary Study

Recently, a specific repetitive transcranial magnetic stimulation (rTMS) waveform, namely, the theta burst stimulation (TBS) protocol, has been proposed for more efficiently inducing neuroplasticity for various clinic rehabilitation purposes. However, few studies have explored the feasibility of using the TBS combined with direct current (dc) waveform for brain neuromodulation; this waveform is transcranially delivered using electrical current power rather than magnetic power. This study implemented a prototype of a novel transcranial electrostimulation device that can flexibly output a waveform that combined dc and the TBS-like protocol and assessed the effects of the novel combinational waveform on neuroplasticity. An in vivo experiment was conducted first to validate the accuracy of the stimulator's current output at various impedance loads. Using this transcranial stimulator, a series of transcranial stimulation experiments was conducted on the brain cortex of rats, in which electrode-tissue impedance and motor evoked potentials (MEPs) were measured. These experiments were designed to assess the feasibility and efficacy of the new combinational waveforms for brain neuroplasticity. Our results indicated that the transcranial electrostimulation system exhibited satisfactory performance, as evidenced by the error percentage of less than 5% for current output. In the animal experiment, the dc combined with intermittent TBS-like protocol exerted a stronger neuroplastic effect than the conventional dc protocol. These results demonstrated that the combination of electrical dc and TBS-like protocols in our system can produce a new feasible therapeutic waveform for transcranially inducing a promising neuromodulatory effect on various diseases of the central nervous system.