Stroke risk and age do not predict behavioral activation of brain blood flow.

Twenty-four neurologically normal subjects, 12 in their twenties and 12 in their sixties, were included in a protocol that studied the relationship of resting cerebral blood flow and cerebral blood flow activation by neuropsychological testing to age and stroke risk factors. Both age and a stroke risk index were predictive of a reduced resting cerebral blood flow. Despite this, cerebral blood flow activation relative to resting flow was preserved. Subclinical lesions of deep white matter are proposed to explain the apparently paradoxical result that resting cerebral blood flow is decreased by factors that damage cerebral vessels, while cerebral vascular reactivity is unimpaired.