Rhythm Effects Of The Endogenous Field On Neural Population

Recent studies have suggested that the endogenous electric fields, i.e. the potential fluctuations in extracellular space, can not only be considered as the observation window of neural activities but also form a feedback on the membranes of adjacent cells by the ephaptic couplings among neurons and may play an important role on network dynamic behaviors. Strong endogenous electric fields induced by the increased extracellular resistances owing to the expanded extracellular volume in low calcium environment may be one of the leading factors of low-calcium seizures during the blockage of synaptic transmission. And effects of relative weak field can be amplified in networks. The hippocampus is the important organization on learning and memory. So we study effects of endogenous field on hippocampus network rhythm.Two kinds of network model have been built, firstly we treat hippocampus vertebral neurons as research objects, In this study, using the simplified mean field to model endogenous field in population and introducing the mean field feedback in chemical or electrical synaptic coupled network, we proved that endogenous filed feedback, as a common and important nonsynaptic interactive method among neurons, may promote the detectability of exogenous electromagnetic field in hybrid coupled neural population. And this promotion can be amplified with the increasing of endogenous coupling strength. Then we analyze the signal transmission mechanism by stochastic resonance from the perspective of neuron spike. This coupling can be used as driving source similar to noise to make network transmit weak signal. And this phenomenon cannot happen when neurons coupled by chemical and electrical synapse.Secondly we built network with vertebral neurons(excitatory neurons) and interneurons(inhibitory neurons) in hippocampal network. Endogenous field is simulated by applied electric field and the effects of different amplitude and different frequency of sine signal on network dynamics. We found weak electric field can modulate network rhythm, especially with the application of sine signal with the same frequency as network rhythm; the network appeared the harmonic oscillation.The effects of endogenous field on signal transmission and detection have been studied and the mechanism has been analyzed. Meanwhile, effects of different direct and alternate current electric field on hippocampal network have been researched. These studies have great meaning to reveal mechanism of exogenous electric field effects on neurons and supply theoretical proof of ephaptic treatment by electric field stimulation.