Functional optical imaging of brain activation: a multi-scale, multi-modality approach

We have developed and applied novel tools for functional optical imaging of the brain. By imaging the brain´s response to stimulus using different modalities, and on different length scales, we can form a more detailed picture of the mechanisms underlying healthy and diseased functional brain activity. One such tool, laminar optical tomography (LOT), is a new technique for 3D, non-contact, high-resolution functional imaging of living tissues. LOT has been used to examine the depth-resolved hemodynamic response to functional activation in exposed rat cortex. LOT has sufficient spatial and temporal resolution to resolve the individual vascular compartments involved in the hemodynamic response (arterial, capillary and venous). To further validate our observations, we also developed a video-rate two-photon microscopy system, capable of imaging at 22 frames per second. We have used this system to create full-field two-photon movies of both the vascular dynamics and calcium-dependent neuronal activity at very high resolution. In addition, we have developed a system for simultaneous exposed-cortex, multi-spectral 2D optical imaging and fMRI at 4.7T. These experiments have allowed us to relate our optical findings to the clinically important BOLD signal