The relationship between visually evoked cerebral blood flow velocity responses and visual-evoked potentials.

A noninvasive assessment of neurovascular coupling would be of great importance. For this reason, we simultaneously studied graded responses of visually evoked cerebral blood flow (CBF) velocity responses (VEFR) and visual-evoked potentials (VEP) to visual contrasts. The records were made from 30 healthy volunteers aged 38.0 +/- 9.6 years. The stimulus was a black-and-white checkerboard with visual contrasts (VC) of 1%, 10%, and 100%. The VEFR were measured in the posterior cerebral artery using transcranial Doppler, and the VEP were recoded from the scalp from occipital leads. To test the relationship between the VEFR and the VEP, a linear regression analysis was performed. We found that the VEFR at 100% VC were 36% higher than those at 10% VC (P < 0.01). The VEFR at 10% VC were 81% higher than those at 1% VC (P < 0.01). The VEP at 100% VC were 76% higher than those at 10% VC (P < 0.01). The VEP at 10% VC were 184% higher than those at 1% VC (P < 0.01). The linear regression showed a significant, moderate association between the VEP and the VEFR (r = 0.66, P < 0.01). The analysis of the regression slopes (b = 0.48 in older subjects vs. b = 0.58 in younger subjects) between two different age subgroups (P < 0.01) did not show any significant difference (P = 0.035). We concluded that a simultaneous recording of VEFR and VEP to graded visual contrasts could allow an assessment of neurovascular coupling.