Effects Of Dendritic Nonlinear Properties On The Neuronal Processing Modulated By External Electric Fields

As a noninvasive brain modulation method,deep transcranial magnetic stimulation(dTMS)can change the excitability of target regions and the activity of nervous system by the induced subliminal electric fields generated in stimulating coil configurations.This technique can decrease the brain tissue damage caused by the clinical treatment.However,there is insufficient understanding of how the induced field influences the neuronal information processing.So we applied the model research method to comprehensively analyze the spatial distribution properties of electric fields and explained the effect of dendritic nonlinear characteristics on the modulation of electric field.Based on the existing hardware platform,we used ANSYS 15.0 of finite element analysis to construct multi-coil array configurations.To demonstrate the effect of spatial arrangement of stimulating coils on electric field properties,we selected various energizing coils to form different combinations.Simulation results show that there is a tradeoff between field attenuation rate and the focality.Compared to traditional figure-8coil,planar and cap-formed arrays have improved penetration depth and focality.The cap-formed array has advantages in precise positioning of target tissues and flexible control.The morphological property of a neuron is an indispensable part of the dendritic nonlinearity.By modeling simplified two-compartment model,we used the ratio between soma and dendrite to quantify the neuron morphology.We depict the relationship between somatic input current,field polarization effect and the initial point of spike.Results show that the polarization of membrane potential is linearly dependent on the strength of electric field.Furthermore,there is an inverse relation between the variation of spiking time and the rate of depolarizing current.The activity of calcium is another critical form of dendritic nonlinearity.Experiments demonstrated that Neurons have multiple firing modes of different temporal scale,here we focus on the spiking form and bursting.Based on the hippocampal pyramidal neurons,we used the two-compartment PR model to complete simulations.Results demonstratethat the variation of DC field intensity can alter the firing model of neurons.Frequency changes of AC field have influence on dendritic spiking properties.The sensitivity of electric field frequency in neurons can be modulated by the distribution of dendritic calcium.This study aims at the modulatory function of electric field on nervous system.By constructing models and analyzing relevant mechanisms,we draw some meaningful conclusions to instruct the optimization of dTMS configurations and neural modeling analysis.