Classification Of Morphological Neuron Types In The Mouse Visual Cortex At Single Neuron Level

As the highest center in the regulation of sensation and movement,the cerebral cortex plays a vital role in animals and human beings' survival.For example,it is inseparable from the cerebral cortex to summarize process and feedback the obtain information,such as visual sense,auditory,olfaction,taste sense and somatic sensation.Especially for human beings,more than 80% of the external information is perceived,received,and processed by the visual system,an essential neural circuit system.Therefore,the visual cortex research is irreplaceable for human beings to understand ourselves and improve ourselves.However,few results on the neural circuits of the visual cortex at the single neuron level are limited by technical means.Therefore,we obtain the datasets of neuronal morphological information and soma' architecture information of the co-location brain datasets based on the high-resolution imaging results in this thesis.On this basis,a series of morphological studies on the visual cortex neurons of mice are carried out,and the following works are specifically completed.(1)A scheme for morphological acquisition and analysis of the individual neuron in the mouse visual cortex was constructed.Based on the advantages of spatial self-registration of the df MOST system,the spatial coordinate range of the visual cortex region is determined according to the soma' architecture information by referring to the Allen Mouse Brain Reference Atlas in our thesis.The neuronal somata on the visual cortex are located by the neuronal morphological information datasets within the corresponding anatomical coordinate range.The neuronal morphology is reconstructed by using the Filament Editor module tool of Amira software interactively on the neuronal morphological information datasets that are transformed to TDat format.The neuronal morphological reconstruction results are tested to ensure the integrity of their morphological structure by the way of backto-back.The topology structure of neuronal files in the digital “.am” format is tested to ensure that the results can be used for the neuronal morphological analysis.(2)In this thesis,103 excitative long-range projection neurons located in layer 5 and layer 6 of mouse visual cortex are reconstructed with two Thy1-e YFP H line mice as the sample.Furthermore,the correlation between neuronal morphology and axonal projection is studied.Based on the following characteristics: the location of the neuronal somata and the shape of the neurons' apical dendrites,the neurons are divided into L5-sp,L5-st,L5-tt,L6-ss,L6-sp and L6-st.Moreover,the dendritic morphology of neurons is quantitatively analyzed based on the distribution in the cortex.According to the axon path and the terminal distribution of the neuronal axon,the axonal projection mode is defined and divided into CFu PN,CPN,and ICCN.Based on the advantages of the neuronal complete morphology,the correlation between 6 types of neurons and three projection modes is analyzed in this thesis.It is found that the dendritic complexity of excitatory neurons in the visual cortex of mice would affect the projection modes of the neuronal axon.When dendrites' complexity is lower,the neurons are more tended to the cortical projection;when the dendrites are more complex,the neurons are more tended to project to subcortical brain regions.For the CFu PN in L5 of the visual cortex,it is found that the cortex,thalamus,midbrain and hypothalamus are the most common target brain regions and cortico-thalamus,cortico-midbrain,thalamusmidbrain,thalamus-hypothalamus,midbrain-hypothalamus,and hypothalamus-pons are the most common projection combinations.Besides,the striatum,pons,and medulla show "high adhesion" in multidirectional projection.The proportion of simultaneous projection to other brain regions is up to 100% when neurons are projected to these three brain regions.In contrast,the CFu PN in L6 in the visual cortex shows typical CT(cortico-thalamic)characteristics.The thalamus is also the main target brain region and cortico-thalamic is the most common projection combination.In addition,it is also found that there is a high similarity in projection patterns between L6-sp and L6-st.(3)In this thesis,47 cholinergic interneurons located in the layer 2/3 and layer 5 of mouse visual cortex are reconstructed with three Chat-Cre:Ai47 mice as the sample.And morphological classification and corresponding difference analysis of these neurons are finished.The molecular characteristic of cholinergic interneurons in the mouse visual cortex obtained in this thesis shows VIP positive through immunohistochemical experiments.And based on the morphology of neurites,the morphological types of these neurons are classified as Bipolar cell(BPC)?Bitufted cell(BTC)and Multi-polar cell(MPC).The neurites of the BPC and BTC types show obvious polarization characteristic perpendicular to the direction of the cortex,while the MPC type does not show this characteristic.On the macroscopic measurement of the complexity,there is a significant difference in the complexity of the neurites between BTC and MPC,while there is no significant difference in the complexity of the neurites between BPC and BTC or between BPC and MPC.The morphological difference between BPC and BTC is mainly characterized by topological features on the hierarchical measurement of the complexity.The morphological differences between BPC and MPC are not only in topological structure,but also in the polarization characteristic of neurons.In summary,a series of studies are finished on the neural circuits of the visual cortex at the single neuron level.The research includes the correlation between the morphological characteristics and the projection brain regions of the excitatory long-range projection neurons and morphological analysis of cholinergic interneurons in the visual cortex.This thesis provides the result analysis at the single neuron level for the neural circuits of the visual cortex.