In Vivo Brain Optical Imaging as a Tool for Studying Animal Models of Neural Disease
Brain optical imaging is based on the idea that the neuron's optical features are highly responsive to functional changes in the neural tissue and the light of different wavelengths can be used to observe the morphological structure and function in vivo in the exposed brain as well as transcranially. In this presentation we overview of the current optical approaches used for the in vivo imaging of the neural activity as well as neurovascular coupling events in small animal models. The basic principles of each technique - optical imaging of intrinsic signal (IOS), voltage-sensitive dye imaging (VSDi) and photoacoustic tomography (PA) are described in detail, followed by examples of current applications from cutting-edge studies of cerebral neurovascular coupling functions and metabolic functions.
Using VSDi we visualized neural activity in the rat somatosensory cortex in response to the deflection of a single whisker in different directions. Obtained data indicates that fast movements of single whiskers in varying directions correlate with different patterns of activation in the neocortex and a functional map was created. Also we would like to provide a glimpse of the possible ways in which these techniques might be translated to human studies for clinical investigations of pathophysiology and disease. Thus, epilepsy mapping with high spatial and temporal resolution has a great significance for both fundamental research of the epileptic seizures and the clinical management of this decease.
In our study we used PA to monitor the hemodynamic changes of the microvasculature surrounding the epileptic neurons. A large vasodilatation of the blood vessels in the area of the epileptic foci signals the onset of the seizure. Although it is unlikely that vasodilatation itself can initiate the seizure, fast vasodilatation might be a first indicator of the local biochemical process that accompanies the seizure’s initiation. In vivo optical imaging techniques continue to expand and evolve, allowing us to discover the fundamental basis of neurovascular coupling roles in cerebral physiology.