| Fear is a basic emotional state,which will be aroused when the creatures face external threats and stimuli.Fear emotion is crucial for animals to defend against danger and obtain survival opportunities.Threat information perceived by animals mainly comes from vision,the subcortical visual pathway is mainly responsible for the rapid processing of fear visual information in two visual pathways that process visual information.Studies have shown that superior colliculus(SC),lateral posterior nucleus of thalamus(LP)and amygdala(AMG)are the key nuclei of the subcortical visual pathway,As the main nucleus of fear information processing,AMG’s neural information processing mechanism has been extensively analyzed.However,the neural information processing mechanism of SC and LP in fear visual coding is still not very clear.Therefore,in order to reveal the coding mechanism of fear visual information in SC and LP of subcortical visual pathway,C57BL/6J mice were used as experimental animals to carry out a series of studies in this thesis.The research results will deepen people’s understanding of brain self-protection and early warning mechanism.Looming stimulus which simulating the predator can induce mice’s instinctive fear,and Dimming stimulus was used as a non-fear control.Spike and local field potential(LFP)signals in the SC and LP of mice under two kinds of visual stimuli were collected.Spike firing rate and FSL characteristics,LFP functional network connection characteristics,and Spike-LFP collaborative coding characteristics were extracted for analysis.And the effect of neuron feature coding was verified by logistic regression model.The specific work and research results are as follows:(1)The mice behavioral experimental apparatus was developed,which includes a visual stimulus presentation system and a behavioral system.The device could set different visual stimulus patterns according to the needs,monitor the behavior of mice under different visual stimuli,and analyze the behavioral parameters(speed,flight latency,etc.).The results show that: Looming stimulation can induce the instinctive fear response in mice,but Dimming visual stimulation can’t.(2)The neural signals in the SC and LP of mice under different visual stimuli were collected and preprocessed respectively,then the Spike firing rate and first spike latency(FSL)characteristics were extracted.The results showed that: fear visual stimulation could significantly increase the Spike firing rate and decrease the FSL time in the SC and LP,indicating that fear information could effectively activate the response of neurons in the SC and LP,and the neuron responds faster under the fear emotion.(3)Power spectrum analysis was used to determine that the characteristic frequency band related to fear emotion in LFP signal was theta band,then the theta bands of SC and LP were extracted respectively.The synchronization likelihood(SL)algorithm was used to construct the brain function network connection in theta band,and the clustering coefficient and global efficiency characteristics of the network under different visual stimuli were extracted for analysis.The results show that: under fear visual stimulation,the network connection of theta band is closer,the transmission efficiency is higher,and the aggregation degree is better,and the theta band of SC and LP can effectively represent fear visual information.(4)Calculate the joint entropy index value between Spike and θ band signals in SC and LP respectively,and analyze the synergistic changes of Spike-LFP under fear visual stimuli,and verify the coding effect of the extracted features through logistic regression model.The results show that: the joint entropy index(JEI)between Spike and theta band increases significantly during fear stimulation,which indicates that spike and theta band can cooperatively and represent fear visual information.The coding effect of the model indicates the effectiveness of extracting neuron coding features and the reliability of the model. |
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