Mean blood flow velocities in posterior cerebral arteries during visual stimulation

Changes of mean blood flow velocities (MBFV) in the posterior cerebral arteries (PCA) recorded during visual stimulation in a group of 51 healthy, right-handed volunteers are presented. There were 27 (52.9%) males and 24 (47.1%) females, aged 20-59 years (mean age: 36.98 years). Measurements were performed with a hand-held 2 MHz transcranial Doppler (TCD) probe through the temporal window, with the subjects' eyes open and closed, and while they were looking at constant and at flashing white light. In half of the subjects, first the right PCA was insonated and then the left PCA, while in the other half the reverse procedure was used. Statistical analysis was done using Wilcoxon's matched-pair signed-rank test. Mean MBFV value in the left PCA was 41.2+/-8.6 cm/s (mean +/- SD) with eyes open, 27.8+/-8.5 cm/s with eyes closed, 42.3+/-9.1 cm/s while looking at constant white light, and 43.0+/-9.6 cm/s while looking at flashing white light. Mean MBFV value in the right PCA was 41.7+/-8.9 cm/s with eyes open, 28.2+/-9.1 cm/s with eyes closed, 42.4+/-8.8 cm/s while looking at constant white light, and 43.4+/-9.2 while looking at flashing white light. Value differences for the left PCA, between eyes open and closed and between looking at constant white light and looking at flashing white light were statistically significant (p<0.001, z= -6.2146, and p<0.001, z= -3.4836, respectively). For the right PCA, a value difference between eyes open and closed, and between looking at constant and flashing white light was statistically significant (p<0.001, z= -6.2146 and p<0.001, z= -3.6928), but there was no significant difference between eyes open and constant white light (p=0.03, z= -2.1693). The results showed that simple visual stimulation had an effect on blood flow velocities in PCA and that it could be measured with TCD.