We have preliminarily examined the use of an intrinsic optical imaging method for monitoring neural activities in mammalian sensory cortices. Optical reflectance changes were detected from the rat somatosensory cortex in response to small whisker movements. For this optical imaging, we used a differential video data acquisition system, IMAGER 2001. This system was composed of a low noise CCD camera that provides a spatial resolution of 756x574 pixels, an analog video enhancement amplifier and high resolution videodisplays. A reference image was subtracted from the video signal. The resulting signal was then amplified and digitized by an 8-bit image processor. For the functional imaging, a single whisker was deflected for 1 or 2 sec while 8 frames of 500 msec each were recorded. The relatively clear optical responses were elicited during the whisker movement, and the response area (spot) appeared to correspond to a barrel.