Abstract #1104

Individual differences in haemoglobin concentration influence BOLD fMRI functional connectivity and its correlations with behaviour

Phillip G D Ward^1,2,3, Edwina R Orchard^1,2,3, Stuart Oldham³, Aurina Arnatkevičiūtė³, Francesco Sforazzini¹, Alex Fornito³, Gary F Egan^1,2,3, and Sharna D Jamadar^1,2,3

¹Monash Biomedical Imaging, Monash University, Melbourne, Australia, ²Australian Research Council Centre of Excellence for Integrative Brain Function, Melbourne, Australia, ³Turner Institute for Brain and Mental Health, Monash University, Melbourne, Australia

The BOLD signal detects changes in relative concentrations of oxy/deoxy-haemoglobin. Thus, individual blood haemoglobin levels may influence the BOLD signal-to-noise ratio in a manner independent of neural activity. In this study, we emulate group-differences in haemoglobin by performing a median split on 524 healthy elderly individuals based on individual measurements of haemoglobin. When compared, the two haemoglobin subgroups showed no differences in cognitive measures, however, significant differences in linear relationships between cognitive performance and functional connectivity were observed in four cognitive tests. Our findings confirm that haemoglobin levels are an important confounding variable in BOLD-fMRI-based studies in the elderly.

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