The Influence Of Synaptic Plasticity In The Neuronal Network

Learning and memory is one of the most important cognitive function of the central nervous system.It is known that synaptic plasticity is the neuronal basis of learning and memory.Further study of synaptic plasticity has a vital effect.Meanwhile,neurons not only receive external stimulation from environment but also are deeply influenced by a variety of different forms of noise.Noise is considered to play a destroy role.However,many experiments show that an appropriate intensity of noise can play a positive effect.It can not only generate action potential spontaneously but also affect their reliability and synchronization,etc.Hence,to investigate the function of noise is important to understand the function of the nervous system.In this paper,we study the combined effect of channel noise and synaptic plasticity on the firing dynamic of neurons through some quantity such as the coefficient of variation,synchronization and synaptic efficacy of the network.We explain the mechanism of neuronal activities and its biological significance.We further consider the short-term and long-term plasticity respectively.In part ?,we study the short-term synaptic plasticity.First of all,we introduce the corresponding model-the UR model and for using of constitute neuronal networks with stochastic Hodgkin-Huxely neurons.Under different levels of noise intensity,we study how the firing rate patterns of a neuronal network is affected by changing the decay rate of inhibition or facilitation.We find that facilitation will promote neuronal network synchronization,while inhibition will destroy the regularity of the network.According to the results,it is shown that neurons will fire synchronously in a proper intensity of channel noise.The duration and stability of working memory can also be regulated by modulating the spontaneous activity of the network.Based on calcium regulation,an FD model is constructed,where we will see how calcium plays a crucial role in synaptic information transmission.In part ?,we present a model to study the long-term synaptic plasticity regulated by NMDA receptors.First of all,we reveal the relation between the membrane area and the probability of vesicle release without external stimuli.Secondly,the probability of vesicle discharge will increase or decrease as neurons are stimulated periodically by changing the stimulus intensity pairs of spikes and the relative time in the pre-and postsynaptic neurons.Thirdly,the pre-and postsynaptic neurons receive different intensities of Pos-sion input.Then we observe the change of firing rate,variation coefficient,synchronous coefficient and vesicle release rate respectively when the excitatory or inhibitory neuron receives different kinds stimulation.Compared with stimulus types,neurons appear res-onance in 60 Hz.NMDA receptors will be activated by neurotransmitters released in synaptic cleft and modify the probability of vesicle discharge as a function of the relative time of spikes in the pre-and postsynaptic neurons in an excitatory neuron.