Research Of Brain Function Based On Optical Imaging And Neural Electrophysiology

Brain is one of the most important organs in human’s body. Its physiological functions and metabolism is complex. There is no energy restoration in the brain, so the oxygen and nutrient supplies are needed in brain activities by continuous blood flow. If the supply of blood flow is blocked or interrupted, neurons lacks oxygen, then damage and necrosis of brain tissue occurs and finally results in stroke. According to clinical observation, cerebral vascular diseases induce brain stroke. In pre-clinical studies of brain injury(like stroke), brain functions need to be monitored in two aspects: blood flow monitoring and nervous system electrophysiology monitoring.Cerebral blood flow imaging provides information of the pathogenesis and pathological processes of cerebrovascular disease. Laser speckle contrast imaging, an important tool for studying brain vasculature and blood supply, provides high-resolution imaging of cerebral blood flow. However, conventional laser speckle contrast imaging has some limitations: spatially inhomogeneous property of scattering results in bias estimation; contrast value is sensitive to various noises making it difficult to identify small blood vessels or analyze functional changes in blood flow. In this study, we developed a correction method in-vivo imaging of rats’ cerebral blood flow. Furthermore, we proposed a new laser speckle imaging method based on small sample entropy. After theoretical derivation and simulation verification, we obtained a linear relation between entropy, exposure time and blood velocity. We also applied the new methods in functional imaging of rats’ cerebral blood flow changes.Ischemic stroke always leads to neuronal death in deep brain regions. The recovery of brain function including functional recovery and regeneration of neurons. This process is slowly. Although the laser speckle imaging can provide high-resolution imaging of cerebral blood flow, it is not efficient for the study of neurons recovery. Neural electrophysiology methods can evaluate brain damage and recovery by monitoring the electrical activity of neurons. It is of great significance to reveal physiological and pathological changes in the nervous system.Clinically, only non-invasive EEG signals can be applied to monitor patients, so it is difficult to know the recovery state of neural functions in deep brain regions. Neural circuits are functional basis for normal brain function. In this study, we explored whether the EEG signals can provide striatum status of damage and recovery based on the direct and indirect pathway between cortex and striatum after temporal middle cerebral artery occlusion(tMCAO).Combining the EEG signal and LFP signal, we got several preliminary results:(1) the changes of peak frequency in EEG power is highly consistent with the change of brain infarction and behavioral scores after stroke.(2) energy of alpha band in EEG signals showed a significant correlation to energy of low gamma band in striatum LFP signals.