Regulation Of Irregular Neuronal Firing By Synaptic Transmission

In cortex,neurons fire spikes highly irregular,which is considered to be linked to many important cognitive functions,such as attention,sensory perception and working memory.Thus,the study on the regulation of neuronal irregular firing is beneficial to the understanding of neural information processing.In this thesis,we systematically study how synaptic transmissions modulate irregular neural firing.The main results are shown as follows:1.Presynaptic bombardments induce and regulate irregular neuronal firing.Firstly,by using the diffusion approximation method,we have derived the analytical expression of synaptic current which appears as a form of Ornstein–Uhlenbeck(OU)noise,and we find that our theoretical results are well agreed with simulation results.Moreover,we find that presynaptic bombardments regulate irregular neuronal firing in a non-monotonic way,and the relatively coherent neuronal firing can be achieved at an optimal presynaptic bombardment level.In addition,we also find that correlated presynaptic bombardments dramatically reduce neuronal firing regularity.In conclusion,our results show that presynaptic inputs play an important role in inducing and regulating irregular neuronal firing.2.Autaptic transmissions modulate irregular neuronal firing.We here show that autaptic transmissions participate in the modulation of irregular neuronal firing,primarily by regulating the occurrence frequency of burst firing.In particular,we find that both excitatory and electrical autapses increase the occurrence of burst firing,thus reducing neuronal firing regularity.In contrast,inhibitory autapses suppress burst firing and therefore tend to improve the regularity of neuronal firing.Moreover,we find that the high-efficiency of autapses in regulating irregular neuronal firing mainly due to the correlation between autaptic current and discharge time of neuron.Furthermore,we show that these findings are independent of the firing properties of individual neuron as well as inputs correlation,and as such can be observed for neurons operating in different modes or receiving correlated presynaptic inputs.Our results provide an insightful mechanistic understanding of how different types of autapses shape irregular firing at the single-neuron level,and these results highlight the functional importance of autaptic transmissions in taming and modulating neurodynamics.In brief,our results provide an insightful mechanistic understanding of the functional role of synaptic transmission in shaping and regulating irregular neuronal firing.Besides,our results are helpful for the understanding of neural information processing due to the importance of irregular neuronal firing in biological neural system.