The assessment of neurovascular coupling with the Addenbrooke's Cognitive Examination: a functional Transcranial Doppler Ultrasonographic Study

Cerebrovascular dysfunction occurs early in dementia and can be identified by Transcranial Doppler ultrasonography (TCD). Few studies have examined cerebral blood flow velocity (CBF_v) responses to a detailed cognitive battery. This study aimed to characterise all CBF_v responses, and the effect of hemispheric dominance, to the Addenbrooke's Cognitive Examination (ACE-III) in healthy volunteers. Forty volunteers underwent continuous bilateral TCD, beat-to-beat blood pressure (MAP) (Finapres), heart rate (HR) (electrocardiogram), and end-tidal CO₂ (ETCO₂) (capnography) monitoring. After 5 minutes baseline, all tasks from the ACE-III were performed in 3 sections (A: attention, fluency, memory, B: language, C: visuospatial, memory). Data are population mean normalised percentage (PM%) change from a twenty second baseline period prior to task initiation. Forty bilateral data sets were obtained (27 female, 37 right-hand dominant). All paradigms produced a sharp increase in CBF_v in both dominant (PM% (range): 3.29 to 9.70%), and non-dominant (PM% (range): 4.34 to 11.63%), hemispheres at task initiation, with associated increases in (MAP) (PM% (range): 3.06 to 16.04%). ETCO₂ did not differ significantly at task initiation (PM% (range): -1.1 to 2.4%, p>0.05). HR differed significantly across the A and C tasks at initiation (PM% (range): -1.1 to 2.4%, p<0.05), but not B tasks. In conclusion, all tasks resulted in increases in CBF_v, differing significantly between paradigms. These results require further investigation in a cognitively impaired population.

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