Laser Doppler speckle contrast imaging of cerebral blood flow during functional activation in rat somatosensory cortex

A laser Doppler speckle contrast imaging (LDSCI) system has been developed for detecting the local cerebral blood flow (LCBF) changes in a living brain with a high temporal (subsecond) and spatial (micrometer) resolution. Near-infrared laser was used to allow the light to penetrate into the cortex beneath the brain surface and the changes in microscopic blood flow were detected due to the laser Doppler effects of moving particles (i.e., Red blood cells) on the speckle change of the imaging. To examine the sensitivity of our LDSCI system, in vivo animal study was performed to investigate activation-flow coupling in somatosensory cortex in response to electrical stimulation of hindpaw in the living rat. The functional hyperemia obtained in this study was in agreement with results from traditional point measurement using Laser Doppler flowmetry. However, the tempo-spatial feature of the LDSCI system would facilitate a better understanding of the mechanism of blood flow-neuronal activity coupling.