Laser doppler imaging of activation-flow coupling in the rat somatosensory cortex.

Activation-flow coupling (AFC) provides a physiological basis for mapping cerebral activation using cerebral blood flow (CBF) as a surrogate marker for neuronal function. Laser Doppler offers a minimally invasive approach for measuring changes in cerebral blood flow but the spatial resolution of this technique is limited by the number of individual probes that can be used. Recently, laser Doppler imaging (LDI) scanners, which use computer-driven optics to scan and measure LD changes in two dimensions, have successfully measured flow changes in the exposed cortex of animals. Here we demonstrate the use of an LDI device through a thinned skull to determine the spatiotemporal characteristics of AFC in alpha-chloralose anesthetized rats in response to electrical forepaw stimulation. The spatial and temporal characteristics of the AFC response measured by LDI are in agreement with prior results obtained using a single LD probe. These results suggest a promising role for LDI in the characterization of the spatiotemporal characteristics of AFC in animal models and possibly for intraoperative monitoring in the human brain.