Extended Data Figure 4. Dilation and velocity responses in parenchymal blood vessels with different baseline diameters.

a, The diameter of all vessels and their OSI values from cat visual cortex layer 2/3. For arterioles, OSI was determined based on dilation (n = 79 vessels in 18 cats) whereas for capillaries, OSI was calculated from blood velocity measurements (n = 15 vessels in 7 cats). b, The distribution of OSI for the three sub-groups of layer 2/3 vessels analyzed in our study (> 15 μm, n = 44 vessels in 15 cats; ≤15 μm, n = 35 vessels in 14 cats; capillaries, n = 15 vessels in 7 cats). The OSI of the ≤15 μm vessels was greater than the OSI of the > 15 μm vessels (P < 0.05; Mann-Whitney test). The OSI of the ≤15 μm vessels was not different from the OSI of the capillaries (P = 0.16; Mann-Whitney test). Solid bars are medians and boxes indicate the inter-quartile range. c, The OSI distribution of dilating vessels and 400-μm-diameter windows of calcium and glutamate responses.