Brain asymmetries from mid- to late life and hemispheric brain age

Abstract

The human brain demonstrates structural and functional asymmetries which have implications for ageing and the development of mental and neurological diseases. We used a set of magnetic resonance imaging (MRI) metrics derived from structural and diffusion MRI data inN= 48,040 UK Biobank participants to evaluate age-related differences in brain asymmetry. Most regional grey and white matter metrics presented asymmetry, which appears lower at higher age. Informed by these results, we conductedhemispheric brain age(HBA) predictions from left/right multimodal MRI metrics, and compared HBA to conventional predictions using metrics from both hemispheres. We present that HBA is concordant to conventional brain age predictions but offers the advantage of supplying a general marker of brain asymmetry when setting left/right HBA into relationship to each other. Similar to brain asymmetries, this discrepancy between left/right HBA is lower at higher ages. The findings emphasise the value of further investigating the role of decreasing brain asymmetries at higher ages in brain ageing and disease development.