Representative results of optical imaging in the rat somatosensory cortex during PT nerve stimulation. (A) CCD image over the left parietal cortex through the cranial window. The bottom right corner of the figure shows 0.5 mm lateral and 0.5 mm caudal from the bregma. Vessels traced with red solid line denote parietal branches of the MCA, and broken lines denote parietal branches of the anterior cerebral artery (ACA). (B) Stimulus-induced activation area measured using voltage-sensitive dye. The map was obtained above 50% of threshold (0.15 ≤ ΔF/F (%) ≤ 0.3) at 28 msec after stimulus onset. Maximal activation of the somatosensory cortex was observed in the hindpaw area. Time courses of changes in membrane potential at the numbered pixels are superimposed (1 and 2, hindpaw area; 3, hindlimb area). (C) Spatial distribution of stimulus-induced absorption change (ΔA577) at 6 sec after stimulus onset. (D) Maximal spatial distribution of intravascular pO2 at 7 sec after stimulus onset. The images were 4 × 5 mm. The somatosensory area could be divided into the following four regions : upper right, predominantly hindlimb area; lower right, predominantly motor area; upper and lower left, predominantly trunk area.