How cerebral circulation has effects on cognitive function?

Abstract

It remains uncertain how brain circulation has effects on cognitive function in aging. Cerebral blood flow (CBF) decreases with advancing ages and in cognitive decline, apparently in vascular dementia and modestly in Alzheimer disease. Brain is an organ which requires enormous amount of CBF and metabolism compared to the other organs, and therefore, cerebral circulation is protected through autoregulation and subsequently, enhancement of oxygen extraction by neuronal structures even when CBF is decreased due to stenosis or obstruction of cerebral vessels.

The damages in the grey matter is relatively mild, but the white matter becomes rarefied with gliosis and nerve fiber loss, if the decrease of CBF remains for a long duration at the level ranging from 50 to 70% of the baseline. In the long run, the patients may exhibit brain atrophy and cognitive decline. The mechanism of dementia in cerebrovascular disease, including small vessel dementia, is relatively straightforward, whereas in Alzheimer disease, it remains unclear how chronic cerebral hypoperfusion may lead to cognitive dysfunction and dementia. Apparently, chronic cerebral hypoperfusion induces neuro–inflammation, disintegration of blood–brain barrier (BBB) and altered excretion of amyloid beta via dysfunction of periarterial drainage pathway and glymphatic system. This review overviews the relationship between cerebral circulation disturbance and cognitive decline with advancing ages.