The Interaction of Dynamic Cerebral Autoregulation and Neurovascular Coupling in Cognitive Impairment.

Abstract

Dynamic cerebral autoregulation (dCA) remains intact in both ageing and dementia, but studies of neurovascular coupling (NVC) have produced mixed findings. We investigated the effects of task-activation on dCA in healthy older adults (HOA), and patients with mild cognitive impairment (MCI) and Alzheimer's Disease (AD). Resting and task-activated data from thirty HOA, twenty-two MCI, and thirty-four AD were extracted from a database. The autoregulation index (ARI) was determined at rest and during five cognitive tasks from transfer function analysis. NVC responses were present where group-specific thresholds of cross-correlation peak function and variance ratio were exceeded. Cumulative response rate (CRR) was the total number of positive responses across five tasks and two hemispheres. ARI differed between groups in dominant (p=0.012) and non-dominant (p=0.042) hemispheres at rest but not during task-activation (p=0.33). ARI decreased during language and memory tasks in HOA (p=0.002) but not in MCI or AD (p=0.40). There was a significant positive correlation between baseline ARI and CRR in all groups (r=0.26, p=0.018), but not within sub-groups. dCA efficiency was reduced in task-activation in healthy but not cognitively impaired participants. These results indicate differences in neurovascular processing in healthy older adults relative to cognitively impaired individuals.