Neural and vascular variability and the fMRI-BOLD response in normal aging

Area of Science:

• Neuroimaging
• Human neuroscience
• Aging research

Background:

• The blood oxygen level-dependent (BOLD) signal is crucial for functional magnetic resonance imaging (fMRI) but exhibits variability.
• Understanding factors contributing to BOLD signal variability is essential for accurate interpretation of brain activity across different age groups.

Purpose of the Study:

• To investigate neural, vascular, and structural contributions to BOLD signal response variability in younger and older adults.
• To compare age-related differences in BOLD signal variability during motor, cognitive, and breath-hold tasks.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure BOLD contrast in 12 younger and 12 older healthy adults.
• Participants performed motor, cognitive, and breath-hold (BH) tasks while undergoing fMRI scans.
• Activation volume and BOLD response amplitude were estimated, and hemodynamic scaling was applied.

Main Results:

• Older adults exhibited reduced activation volume (38-45%) compared to younger adults across tasks.
• BOLD signal variability was significantly higher in older adults, predominantly due to vascular factors during motor tasks.
• Task type influenced the origin of BOLD signal variability, with motor tasks showing more vascular influence and cognitive tasks showing more neural influence.

Conclusions:

• Age-related differences in brain functional response are influenced by both gray matter volume and task-specific vascular variability.
• The type of task performed significantly impacts the interpretation of age-related changes in BOLD signal variability.
• Vascular and neural contributions to BOLD signal variability differ between motor and cognitive tasks and across age groups.