A Mechanism Study On The Induction,Propagation And Encoding Of Transient Neural Activity

A central topic of neuroscience is to elucidate the principle of neural information processing.The classical population coding theory holds the viewpoint that steady-state collective neural activities are underlying multiple brain functions,such as perception,cognition,and behavior.However,recent experiments have widely observed the spontaneous and task-evoked transient firing activities within neural populations.In this thesis,by taking advantage of the computational neuroscience method in uncovering the principle of neural dynamics,a mathematical model of a local brain area was built.The computational simulations were carried out to examine the dynamical mechanism underlying the induction of transient neural activities,and the principle behind efficient,stable transmission and encoding of transient activity.The abstract of the main results and conclusions are shown as follows:(1)Heterogeneity of synaptic input connectivity regulates neuronal avalanches.Experimental measures have widely observed that spontaneous transient population activities emerge in the mammalian cortex,which is organized as scale-invariant neuronal avalanches,suggesting the self-organized criticality of cortical dynamics.Self-organized criticality has been proposed as an overriding neuronal organizing principle for explaining the multi-scale cortical activities and results in the optimal information processing of the neural network.Recently,it has been found that synaptic connectivity of cortical neurons is highly heterogeneous,and neurons exhibit different degrees of structural heterogeneity in their input and output connectivity.To study whether structural heterogeneity participates in the regulation of neuronal avalanches,a heterogeneous neuronal network model is built.By computational modeling,we predict that different types of structural heterogeneity contribute distinct effects on avalanche neurodynamics.By increasing input heterogeneity,the state transition of collective firing activity from synchronous to asynchronous occurs,which corresponds to phase transitions between supercritical,critical,and subcritical dynamics.In particular,neuronal avalanches can be triggered at an intermediate level of input heterogeneity,but heterogeneous output connectivity cannot evoke avalanche dynamics.In the criticality region,the co-emergence of multi-scale cortical activities is observed,and both the avalanche dynamics and neuronal oscillations are modulated by the input heterogeneity.Remarkably,similar results can be reproduced in networks with various types of in-and out-degree distributions.Overall,these findings not only provide details on the underlying circuitry mechanisms of nonrandom synaptic connectivity in the regulation of neuronal avalanches,but also shed light on the understanding of how the network structure relates to the spontaneous transient neural activities and functions in the cortex.(2)Induction and propagation of transient synchronous activity in neural networks endowed with short-term plasticity.Transient synchronous activity is thought to be crucial for flexible communication between microcircuits in distinct cortical regions.The mechanisms underlying induction and propagation of transient synchronous activity are still unknown,and we propose that short-term plasticity of neural circuits may serve as a supplemental mechanism therein.By computational modeling,we showed that the memory buffer of short-term facilitation significantly improves the induction of transient synchronous activity in the local recurrent neural network,and the facilitation time constant determines the optimal timing of the reactivation of transient synchronous activity.Furthermore,we demonstrated that synaptic facilitation dramatically improves the propagation of transient neural activity in the feedforward neural network and that response timing mediated by synaptic facilitation offers a scheme for flexible information routing.In addition,we verified that synaptic strengthening of intralayer or interlayer coupling enhances synchrony propagation,and we verified that other factors such as the delay of synaptic transmission and the mode of synaptic connectivity are also involved in regulating synchronous activity propagation.Overall,our results highlight the functional role of short-term plasticity in regulating the induction and propagation of transient synchronous activity and suggest short-term plasticity may serve as the critical mechanism underlying flexible information routing in the cerebral cortex.(3)Layer-specific population rate coding in a local cortical model with a laminar structure.Uncovering the principle of neural coding is essential for understanding how our mysterious brain works.Recent studies have reported the laminar differences of alphabeta and gamma rhythms in the sensory cortex,yet it remains unclear about the underlying function role of frequency-dependent interlaminar interactions in neural coding.Using a rate-based network model to simulate the cortical laminar under the external time-varying stimuli,we showed that the physiological specificity of rhythms for layers enables the cortical laminae to preferentially encode information in different frequency ranges.The interplay of the supragranular layer and infragranular layer contributes significantly to improving the neural representation of external time-varying input at the population level.Further,our results emphasized the essential role of recurrent connections of the cortical laminae in regulating the population rate coding.The laminar network optimally encodes the time-varying input at intermediate strengths of intralaminar excitatory-inhibitory circuits and the interlaminar connections.Moreover,we verified the crucial role of adaptation in improving population coding by introducing slow dynamics and suppressing the noise-like excitatory activity in the laminar network.In conclusion,our work highlights the crucial role of frequency-dependent interlaminar interactions in encoding time-varying stimuli and may shed light on the underlying function of cortical structural specificity in neural information processing.In conclusion,our study revealed the neural mechanisms underlying the induction,propagation,and encoding of transient neural activity,suggests the underlying role of transient neural activity in high-efficient neural information processing.The results will be helpful for understanding the intrinsic dynamic properties and circuits mechanism of the transient neural activity in spontaneous state.Meanwhile,our study also suggests the crucial role of intrinsic properties of the brain in regulating the stimuli-evoking transient neural activity,which provides the structural and functional basis for efficient and reliable neural information processing.Our work not only help us to understand the fundamental principles of cortical computation,but also inspire testable hypotheses for future experimental studies.