Electrical Neurostimulation Based On Temporally Interfering

Electrical neurostimulation plays a pivotal role in the treatment of nervous system diseases because it can directly modulate the nerve circuit and neuronal function via applying electrical current to the human body.The traditional implantable electrodes have been widely used in clinical treatment due to their high precision both in time and space.However,implantable electrodes are associated with invasion and high surgical costs,so noninvasive transcranial stimulation has been emerged.Transcranial electrical stimulation techniques apply constant and low-intensity currents on the scalp to modulate the neural activity of the cerebral cortex without invasion.Noninvasive transcranial electrical stimulation has a trade-off between spatial resolution and stimulation depth,so it still faces great challenges in technology.One of the important ways to achieve the above requirements is adopting kilohertz-frequency current with better penetrability in human tissue and analyzing the specific mechanism of stimulus currents acting on neurons.This dissertation focused on temporally interfering electrical neurostimulation.Numerical computational model,including electric field and neural ion channels,is established to analyze the mechanism that pre-modulated kilohertz-frequency envelope current and temporally interfering current stimulate deep nervous system.In addition,a multiple modulation stimulation method with high spatial resolution based on temporally interfering electric field is proposed.This dissertation completes the following three aspects:1.Analyze the mechanism of pre-modulated kilohertz-frequency envelope current in tissue from perspectives of electric field and neuronal action potential,including the permeability of kilohertz-frequency current and neuronal low-pass characteristic.The selection of optimal carrier frequency and the electric field distribution of electrodes in different shapes are analyzed in detail.Additionally,a concentric square electrode with high focality is proposed.2.Build numerical computational model,including electric field and neuronal ion channels to describe the mechanism of temporally interfering electric field in human tissue.According to the perspective of superposition principle of two electric fields in time domain,singlecompartment and multi-compartment neuronal model are established to analyze the effects of temporally interfering current acting on neurons,including firing event,neuronal fatigue and conduction block.3.Multiple modulation(frequency,polarity and time division modulation)stimulation method with high spatial resolution.There are two detailed forms about this method: brain focal stimulation and electrodes array.A computational model combining electric filed and neuronal ion channels,measuring distribution of stimulus waveforms in saline solution,and evaluating the effect of measured stimulus waveform on neurons are combined to verify the correctness and focality of this method.