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

doi:10.1093/cercor/bhs233

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 journal › Article › peer-review

45 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 language	English (US)
Pages (from-to)	2337-2346
Number of pages	10
Journal	Cerebral Cortex
Volume	23
Issue number	10
DOIs	https://doi.org/10.1093/cercor/bhs233
State	Published - Oct 2013
Externally published	Yes

Keywords

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

ASJC Scopus subject areas

Cognitive Neuroscience
Cellular and Molecular Neuroscience

Access to Document

10.1093/cercor/bhs233

Cite this

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

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.",

keywords = "Aging, BOLD, CBF, CMRO, Dual-echo ASL, Hypercapnia, Neural efficiency, Processing efficiency",

author = "Hutchison, {Joanna L.} and Hanzhang Lu and Bart Rypma",

note = "Funding Information: This work was supported by the National Institutes of Health (1R01AG029523 [to B.R.] and R01MH084021 [to H.L.]). Funding to pay the Open Access publication charges for this article was provided by the National Institute of Health (1R01AG029523 [to B.R.] ).",

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AU - Rypma, Bart

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N2 - 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.

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