Individual differences in haemoglobin concentration influence bold fMRI functional connectivity and its correlation...

Area of Science:

• Neuroscience
• Medical Imaging
• Human Physiology

Background:

• Resting-state functional connectivity (rsFC) is commonly measured using Blood-Oxygen-Level-Dependent functional Magnetic Resonance Imaging (BOLD-fMRI).
• The BOLD signal reflects changes in blood oxygenation, influenced by hemoglobin concentration.
• Individual variations in hemoglobin may independently affect BOLD signal-to-noise ratio, potentially confounding rsFC.

Purpose of the Study:

• To investigate if group differences in hemoglobin confound rsFC measures.
• To examine if hemoglobin variability influences the relationship between rsFC and cognitive performance.
• To map the neuroanatomical distribution of hemoglobin's influence on rsFC.

Main Methods:

• Analysis of rsFC in 518 healthy elderly subjects (259 men).
• Median-splitting participants by hemoglobin concentration within each sex group.
• Assessing differences in rsFC, sex-specific effects, and relationships between rsFC and cognitive tests.

Main Results:

• Significant differences in rsFC were found between high and low hemoglobin groups in both men and women.
• Hemoglobin influenced the connectome differently across sexes: widespread increases in males, and parietal/subcortical increases with temporo-parietal decreases in females.
• Despite no cognitive differences between hemoglobin groups, significant differences in connectivity-cognition relationships were observed, particularly in males.

Conclusions:

• Individual hemoglobin variability is a significant confounder in BOLD-fMRI rsFC studies.
• Controlling for hemoglobin is essential for reproducibility in human brain connectome research, especially when comparing groups, sexes, or examining cognition relationships.