The Effect Of Athorny Pyramidal Cells In Hippocampal CA3 On Pattern Completion

The CA3 area of the hippocampus is thought to implement pattern completion by attractor dynamics.Understanding the mechanism of this computational process at the level of cellular and ensemble activities is crucial for elucidating the neural correlates of cognition with CA3.A novel type of heterogeneous pyramidal cell,which is called athomy pyramidal cell due to lack of dendritic spines,is recently identified in CA3.It is proposed that such heterogeneous neurons may be involved in mnemonic cognitive functions.However,the significance of this heterogeneous neuron remains unclear.To investigate whether and how these heterogeneous neurons play a role in cognitive activities,we construct a simple,biologically relevant CA3 network model.The main work and results are summarized as follows:We comprehensively investigated the effect of the athorny pyramidal cells on the pattern completion of the CA3 model.Firstly,we considered the influence of athorny pyramidal cells on pattern completion.The results indicate that the effect of athorny pyramidal cells on pattern completion is robust.Adjusting the ratio of athorny pyramidal cells and the synaptic coupling strength with thorny pyramidal cells within a certain range can enhance pattern completion.Subsequently,the mechanism of athorny pyramidal cells to enhance pattern completion was analyzed.We found that compared with the thorny pyramidal cells,the athorny pyramidal cells have a better performance in pattern completion due to their more excitability and the burst firing pattern,and the analysis of dynamic characteristics shows that the athorny pyramidal cells are in the "short facilitation window of synaptic efficacy" increases the NMDA current to enhance pattern completion.Finally,a three-coupled neuron model was constructed to illustrate the mechanism of the athorny pyramidal cells on pattern completion.Besides,we also studied the influence of the synaptic plasticity mechanism STDP on the CA3 network.Our research demonstrates that the model parameters of STDP have an important impact on synaptic modification.the depression scale factor controlling the amplitude of LTD affects the trend direction of synaptic strength in modification.secondly,the width of the STDP time window affecting the synaptic modification depends on neuron firing frequency.Then the phenomenon of synaptic modification stability was studied.We found that increasing the negative feedback regulation of inhibitory interneurons helps to maintain the synaptic modification and firing stability of the neuron population.Finally,the influence of sparsity of network connectivity on synapse modification is studied.Our results show that when the neural network becomes sparse,the unidirectional connection has a more positive biased temporal difference of spike than the bidirectional connection,which presents a continuous increasing tendency of synaptic strength.