A BOLD Perspective on Age-Related Neurometabolic-Flow Coupling and Neural Efficiency Changes in Human Visual Cortex
Joanna Lynn Hutchison1, Ehsan Shokri-Kojori, Hanzhang Lu
1School of Behavioral and Brain Sciences, University of Texas at Dallas Richardson, TX, USA ; Department of Psychiatry, University of Texas Southwestern Medical Center Dallas, TX, USA.
Frontiers in Psychology
|May 9, 2013
Summary
Age-related visual task declines may stem from reduced neural efficiency. Studies show age-related decreases in the coupling of cerebral blood flow (CBF) and oxygen metabolism (CMRO2) lead to misinterpreted blood-oxygen-level-dependent (BOLD) signals.
Area of Science:
- Neuroscience
- Aging Research
- Medical Imaging
Background:
- Age-related declines in visual task performance are often linked to reduced neural processing efficiency.
- The blood-oxygen-level-dependent (BOLD) signal is commonly used to infer neural activity changes with age, but its interpretation is complex.
- BOLD signal differences between age groups may arise from factors beyond neural activity, such as changes in cerebral blood flow and metabolism.
Purpose of the Study:
- To investigate the origin of age-related BOLD signal changes by examining the interplay between cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2).
- To determine if age-related differences in neurometabolic-flow coupling contribute to observed BOLD signal variations and impact visual task performance.
Main Methods:
- Utilized magnetic resonance dual-echo arterial spin labeling and CO2 ingestion to measure fractional cerebral blood flow (ΔCBF) and fractional cerebral metabolic rate of oxygen (ΔCMRO2) in older and younger adults.
- Subjects performed a visual detection task involving luminance changes, with reaction times recorded.
- Simulated BOLD signal changes relative to ΔCMRO2 using varying neurometabolic-flow coupling ratios to model age-related differences.
Main Results:
- Observed age-equivalent ΔCBF despite age-related increases in ΔCMRO2.
- Identified reduced responsiveness of ΔCBF to increased ΔCMRO2 in older adults, leading to paradoxical age-related BOLD decreases.
- Found that decreases in the ΔCBF/ΔCMRO2 ratio correlated with slower reaction times, suggesting reduced neural efficiency.
Conclusions:
- Age-related BOLD signal changes in visual tasks may not solely reflect neural activity but also altered neurometabolic-flow coupling.
- Reduced vascular responsiveness to metabolic demand in aging can lead to less efficient neural activity and impaired task performance.
- Findings suggest that age-comparative BOLD studies require careful interpretation due to potential confounds from changes in CBF and CMRO2 dynamics.
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