Abstract
Transcranial electrical stimulation (TES) is a widely accepted neuromodulation modality for treating brain disorders. However, its clinical efficacy is fundamentally limited due to the current shunting effect of the scalp and safety issues. A newer electrical stimulation technique called subcutaneous electrical stimulation (SES) promises to overcome the limitations of TES by applying currents directly at the site of the disorder through the skull. While SES seems promising, the electrophysiological effect of SES compared to TES is still unknown, thus limiting its broader application. Here we comprehensively analyze the SES and TES to demonstrate the effectiveness and advantages of SES. Beagles were bilaterally implanted with subdural strips for intracranial electroencephalography and electric field recording. For the intracerebral electric field prediction, we designed a 3D electromagnetic simulation framework and simulated TES and SES. In the beagle model, SES induces three to four-fold larger cerebral electric fields compared to TES, and significant changes in power ratio of brainwaves were observed only in SES. Our prediction framework suggests that the field penetration of SES would be several-fold larger than TES in human brains. These results demonstrate that the SES would significantly enhance the neuromodulatory effects compared to conventional TES and overcome the TES limitations.
Highlights
Transcranial electrical stimulation (TES) is a widely accepted neuromodulation modality for treating brain disorders
The intracranial electric fields induced by TES and subcutaneous electrical stimulation (SES) techniques were measured to quantify the attenuation of the electric field via the scalp tissue using beagle models
Two 8-channel subdural strips were inserted between the skull and the brain (Fig. 1) through the drilled holes, and a needle electrode was inserted into the thigh to be served as the reference electrode for recording intracranial electric fields
Summary
Transcranial electrical stimulation (TES) is a widely accepted neuromodulation modality for treating brain disorders. A newer electrical stimulation technique called subcutaneous electrical stimulation (SES) promises to overcome the limitations of TES by applying currents directly at the site of the disorder through the skull. Our prediction framework suggests that the field penetration of SES would be several-fold larger than TES in human brains These results demonstrate that the SES would significantly enhance the neuromodulatory effects compared to conventional TES and overcome the TES limitations. Et al.[16], estimated that, when applied transcutaneously, approximately 6 mA of current, which is beyond the safety limit for tDCS17,18, is needed to generate sufficient electric field to modulate neuronal circuits in human brains. Extensive comparisons between SES and TES to evaluate the practicality, safety and clinical effectiveness of subcutaneous stimulation compared to transcutaneous stimulation are still unknown, limiting its broader application
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