Multi-modal Optical Imaging Method In Deep Brain Areas In Awake Animals

Brain functional optical imaging plays an important role in neuroscience because of its high spatial and temporal resolution.Multi-mode optical imaging methods is becoming a powerful tool for exploring changes in brain function with its characteristics of multiparameter simultaneous measurement.However,limited penetration of light into tissue precludes intravital microscopy in deep areas,while many pathologies(such as stroke,Alzheimer's syndrome,Parkinson's syndrome,etc.)afflict deeper brain structures such as hippocampus or thalamus.In the past decades,most of the researches in neuroscience have been carried out on anesthetized animals,and only a few in awake.However,the main purposes of neuroscience research are to explore the mechanisms of neural activity such as perception,behavior,learning and memory.Only in awake animals can we study the function of the nervous system when the animal perceives and expresses behavior in a specific environment.Therefore,new technologies and methods which can be applied in deep brain regions as well as in conscious animals are urgently needed in order to explore the changes in structure and function in deep brain regions and the relationship between behavior and neural activities in related neurological diseases.In this paper,we present a multi-modal imaging system based on invasive gradient index(GRIN)lens which have achieved cellular-level time-lapse fluorescence and hemodynamic detection in deep brain in anesthetized and awake animals.Using this system,we successfully recorded GCa MP6 fluorescent signals and cerebral blood flow(CBF)obtained by laser speckle contrast imaging(LSCI)from the ventral posteromedial nucleus(VPM)in thalamus of a head-restrained mouse during cortical spreading depression(CSD).The main research results are as follows:(1)A LSCI method based on GRIN lens for time-lapse blood flow detection in subcortical regions of the brain is presented.We monitored the hemodynamic changes in the thalamus of mouse models of acute hypoxia and transient middle cerebral artery occlusion(t MCAo)as a proof of concept for practical applications.The results showed that the relative changes of CBF in the cortex and thalamus are similar during acute hypoxia,but had distinction to some extent;the MCAo had different effects on the bilateral thalamus.It suggests that there may be different regulatory and protective mechanisms for the cortex and thalamus in brain.(2)A multi-modal imaging system based on invasive GRIN lens which have achieved cellular-level time-lapse fluorescence and hemodynamic detection in deep brain is presented.The system combines GCa MP6 fluorescence imaging and laser speckle blood flow imaging in deep brain regions through a head-mounted microscopic imaging system and it allows simultaneous detection of the relative changes of neural activity and CBF in the deep brain region,the electrophysiological signal in the cortex and the body movement information.The system is integrated and controlled by Lab VIEW software,which enables stable and efficient data collection.(3)The neural activity and hemodynamic changes were recorded from the VPM in thalamus of a head-restrained mouse in both anesthetized and awake during CSD.The results show that induction of unilateral CSD can significantly activate excitatory neurons(VGlu T2)in ipsilateral VPM only in the awake state.It suggests that CSD can activate the trigeminal pathway and consciousness plays an important role in it,which contributes to migraine headaches.