Characterization of optical intrinsic signals and blood volume during cortical spreading depression

Cortical spreading depression (CSD) was imaged in vivo in a rodent model wi th optical intrinsic signals (OIS). This is the first study to identify a t riphasic OIS response and to characterize the rate and timing of the respon se. The initial OIS phase had a highly uniform wavefront, which spread at a rate characteristic of CSD, 3.5 mm/min. Later phases were more diffuse and inhomogeneous. Blood volume changes, measured with intravascular fluoresce nt dye, correlated in time and location with the later phases of OIS repons e. This suggests that the inhomogeneity of the late OIS response may be due to complex residual hemodynamic contributions, as opposed to underlying co rtical circuitry. NeuroReport 11:2121-2125 (C) 2000 Lippincott Williams & W ilkins.