Age and stimulus dependency of visually evoked cerebral blood flow responses

Background and Purpose-During visual stimulation, the increased metabolic d emand is coupled with an increase of cerebral blood flow velocity (pCBFV) i n the posterior cerebral artery (PCA). Investigation of the visually evoked flow responses (VEFR, expressed as percentage of increase from baseline pC BFV values) was suggested for different conditions:of vasoneuronal disorder s in the absence of any systematic investigation in healthy subjects. Methods-We investigated VEFRs from both PCAs to various increasingly comple x paradigms (diffuse light, alternating checkerboard patterns, and a color video movie stimulation; 5, 10, 20, and 30-second intervals) in 60 healthy volunteers (mean age, 41.5+/-14.9 years; range, 24 to XO years; 28 male, 32 female) at different recording sites (P1 versus P2 segments of PCAs). Results-With increasing complexity of stimulation, the VEFRs increased sign ificantly (24.3+/-10.3%, 28.5+/-13.5%, and 43.4+/-10.7%, respectively). Twe nty-second stimulation intervals yielded maximal responses (41.5+/-13.2%) c ompared with 5-, 10-, and 30-second intervals (22.6+/-14.1%, P=0.001; 34.4/-11.7%, P=0.0042; and 35.5+/-9.9%, P=0.0032, respectively). Significantly higher responses were gained from P2 segments than from P1 segments (42.7+/ -7.2% versus 28.2+/-7.1%). Although VEFRs tended to decrease in amplitude w ith age (mean, 41.7+/-10.5% [20 to 40 years], 35+/-9.2% [40 to 60 years], a nd 33.9+/-8.6% [60 to 80 years]); without significant sex-related differenc es, only the percentage decrement of the pulsatility indices during stimula tion were significant (mean, 24+/-10.7% [20 to 40 years], 20+/-7.3% [40 to 60 years], and 13+/-11.2% [60 to 80 years]). Conclusions-For optimal stimulus conditions for maximum VEFRs, a colored vi deo stimulation of 20-second intervals should be used to combine responses not only from the primary Visual projection fields (V-1 and V-2) but also f rom temporal lobe areas (V-3 through V-5) often supplied by the PCA.