The Mechanism Research Of Theta Oscillations By Visual Stimuli In Primary Visual Cortex Of Mice

Information processing in the brain relies on the dynamic interactions between different neuronal populations.Neuronal oscillations are integration of all transmembrane ion currents,and reflect the dynamic interactions between neuronal populations.Neuronal oscillations in the brain are thought to underlie several functions,including sensory information processing,motor control,cognition,as well as synchronization between brain areas.Some neuropsychiatric diseases are usually characterized by abnormal or defective neuronal oscillations at specific frequency bands in certain brain regions.Induction of specific frequency oscillations with a certain way has an effect on treating neuropsychiatric diseases and improving cognition.Therefore,it is of great significance to elucidate the circuits mechanism of the neuronal oscillations,which contributes to understanding the information processing and pathogenesis of some neuropsychiatric disorders.Various forms of neuronal oscillations in the primary visual cortex(V1)are thought to underlie the processing of spatiotemporal information carried by visual stimuli.Oscillatory activities within the visual system have been implicated in visual information processing,synchronization between brain areas,selective attention and working memory.Distinct subtypes of GABAergic neurons are known to play a vital role in regulating diverse rhythmic activities in the cortex.Visual stimuli enhance theta oscillations in V1 of mice;however,the detailed mechanisms remain unknown.The theta oscillations are generated by a consortium of mechanisms,including the intrinsic characteristics of individual neurons,a septal pacemaker and neural circuit interactions.A potential mechanism for theta generation is the resonant properties of neurons.In this study,the author uses extracellular recordings of local field potentials(LFPs),multichannel recording,optogenetically tagged specific subtypes of neurons and optogenetic manipulation to explore the neural activity of V1 in response to visual stimuli,as well as theta oscillations governed by specific subtypes of GABAergic neurons.The main contents as follows:(1)The author has demonstrated that visual stimuli enhance theta oscillations in V1,theta oscillations positively correlate to stimulus intensity;theta oscillations are modulated by behavioral state,anesthetization and locomotion inhibit theta oscillations;theta oscillations are modulated by visual stimulus contrast,decrease of the contrast between visual stimuli and the environment inhibits visual stimuli-induced theta oscillations;theta oscillations are stimulus-modality specific,auditory stimuli do not enhance theta oscillations;visual stimuli enhance spike-phase locking in low-theta(3~7 Hz)band with extracellular recordings of LFPs and single unit.(2)The author has showed that visual stimuli facilitate SOM neuron responses,whose activities are positively correlate to stimulus intensity;visual stimuli enhance SOM neurons spike-phase locking in low-theta band;visual stimuli enhance PV neurons spike-phase locking in low-theta band,but suppress their activities,which activities are negatively correlate to stimulus intensity;locomotion attenuates neurons spike-phase locking in lowtheta band by recording optogenetically tagged specific subtypes of GABAergic neurons.(3)The author has revealed that inactivation of SOM neurons changes tuning properties of neurons to visual stimuli and attenuates the enhancement of theta oscillations induced by visual stimuli,as well as neurons spike-phase locking in low-theta band;rhythmical activation of SOM neurons enhances theta oscillations with bidirectional optogenetic manipulation.The author has also demonstrated that visual stimuli enhance theta coupling between V1 and m PFC,V1 theta oscillations leading those in m PFC by extracellular recordings of LFPs.In summary,this study have demonstrated that theta enhancement by visual stimuli are modulated by stimulus intensity,behavioural state,the external environment and are stimulus-modality specific.Visual stimuli facilitate SOM neuron responses and spike-phase locking in low-theta band;visual stimuli enhance PV neurons spike-phase locking in lowtheta band but inhibit PV neurons activities;SOM neurons govern theta oscillations.It is revealed that a potential cortical theta oscillation mechanism governed by SOM neurons in V1.This study further clarify the neural dynamic changes of V1 in visual information processing.This study deepen the understanding of the mechanism of different frequency bands oscillation in V1.