Hemispheric asymmetries in blood flow during color stimulation.

Visual stimulation influences mean blood flow velocities (MBFV) in posterior cerebral arteries (PCA). In 51 healthy, right-handed volunteers MBFV were measured in PCA with opened and closed eyes and while watching colored light (red, yellow, green, blue) for 1 minute. Volunteers had eyes closed 2 minutes between different colors. MBFV in left PCA was 41.2 +/- 8.6 cm/s (mean +/- 2SD) and 27.8 +/- 8.5 cm/s with eyes opened and closed, respectively. For red light MBFV in left PCA was 31.4 +/- 7.1 cm/s, for yellow 31.4 +/- 7.2 cm/s, for green 32.0 +/- 8.3 cm/s, and for blue 33.0 +/- 7.6 cm/s. MBFV in right PCA 41.7 +/- 8.9 cm/s and 28.2 +/- 9.1 cm/s with eyes opened and closed, respectively. For red light MBFV in right PCA was 39.4 +/- 8.4 cm/s, for yellow 38.9 +/- 9.2 cm/s, for green 37.8 +/- 9.4 cm/s and for blue 38.0 +/- 8.8 cm/s. There was no significant difference in MBFV between left and right PCA with eyes opened and closed, but MBFV were significantly higher in right PCA for each color than corresponding MBFV in left PCA. These findings could indicate the greater metabolism of visual cortex in right occipital lobe while watching colors. Visual cortex of right occipital lobe could have greater importance in color perception than visual cortex of left occipital lobe.