Age-related changes in the relationship between visual evoked potentials and visually evoked cerebral blood flow velocity response.

We evaluated neurovascular coupling during normal aging using visual evoked potentials (VEPs) and visually evoked cerebral blood flow velocity responses (VEFRs). The recordings were made from a group of healthy younger and older subjects. The stimulus was a black and white checkerboard with visual contrasts of 1%, 10% and 100%. The VEFRs were measured in the posterior cerebral artery using transcranial Doppler simultaneously with VEPs from occipital leads. A significant increase in the VEFRs and VEPs in response to graded visual contrasts (p<0.01) was found in both groups. Linear regression analysis showed a significant positive association between the VEPs and the VEFRs in the younger (r=0.66, p<0.01) and older subjects (r=0.74, p<0.01). We also found significant differences in neurovascular coupling index (VEFR/VEP) between both groups at each visual contrast (p<0.01). We conclude that simultaneous recording of VEFRs and VEPs at graded visual contrasts indicated attenuated neurovascular coupling in older subjects.