Stimulus-induced changes in pial arteriolar blood flow and diameter in the somatosensory cortex. (A) Comparison of the time course of rCBF measured using LDF and blood-flow rate in individual pial arterioles measured using FLDAM. Vessels labeled A are second-order branches of MCA (32.7 μm ± 14.3 SD in diameter), those labeled B are third-order branches (25.0 μm ± 11.3 SD) supplying the hindlimb (hindpaw) somatosensory area, and those labeled C are third-order branches (24.3 μm ± 11.1 SD) predominantly supplying the trunk area (see Fig. 2A). Normalized time course-changes in diameter are shown in the inset. Averaged values from 15 trials of 5 rats are shown; the errors for each data point are less than 10%. (B) Illustration of blood-flow regulation in the somatosensory cortex during PT nerve stimulation. F.I. denotes flow increase. The flow data shown were from (A).