Neural mechanisms of age-related slowing: The ΔCBF/ΔCMRO 2 ratio mediates age-differences in BOLD signal and human performance

Joanna L. Hutchison, Hanzhang Lu, Bart Rypma

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

The precise mechanisms that give rise to the blood-oxygen-level-dependent (BOLD) activation differences that accompany age-related cognitive slowing remain fundamentally unknown. We sought to isolate the origin of age-related BOLD changes by comparing blood-flow and oxygen-metabolic constituents of the BOLD response using dual-echo arterial spin labeling during visual stimulation and CO2 ingestion. We hypothesized, and our results confirmed, that age-related changes in the ratio of fractional cerebral blood flow to fractional cerebral metabolic rate of oxygen consumption (ΔCBF/ΔCMRO 2) lead to the BOLD changes that are observed in older adults. ΔCBF/ΔCMRO2 was also significantly related to performance, suggesting that age-related cognitive slowing results from neural cell assemblies that operate less efficiently, requiring greater oxygen metabolism that is not matched by blood-flow changes relative to younger adults. Age-related changes in ΔCBF/ΔCMRO2 are sufficient to explain variations in BOLD responding and performance cited throughout the literature, assuming no bias based on physiological baseline CMRO2.

Original languageEnglish (US)
Pages (from-to)2337-2346
Number of pages10
JournalCerebral Cortex
Volume23
Issue number10
DOIs
StatePublished - Oct 1 2013

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Keywords

  • Aging
  • BOLD
  • CBF
  • CMRO
  • Dual-echo ASL
  • Hypercapnia
  • Neural efficiency
  • Processing efficiency

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Cellular and Molecular Neuroscience

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