Age-related changes in brain asymmetry and the (missing) impact of brain size, sex, and intelligence

Poster No:

879 

Submission Type:

Abstract Submission 

Authors:

Eileen Luders1, Nicolas Cherbuin2, Christian Gaser3, Florian Kurth3

Institutions:

1The University of Auckland, Auckland, New Zealand, 2The Australian National University, Canberra, Australia, 3University of Jena, Jena, Germany

First Author:

Eileen Luders  
The University of Auckland
Auckland, New Zealand

Co-Author(s):

Nicolas Cherbuin, PhD  
The Australian National University
Canberra, Australia
Christian Gaser  
University of Jena
Jena, Germany
Florian Kurth  
University of Jena
Jena, Germany

Introduction:

Structural and functional differences between the hemispheres change with age. Some theories suggest a progressive recruitment of homotopic contralateral brain regions, which may manifest as decreases in asymmetry. Other theories suggest an accelerated atrophy of one hemisphere compared to the other, which may manifest as increases in asymmetry. Here we set out to analyze age-related changes in brain asymmetry using a large sample (n=1,725) of healthy participants. In addition, we investigated whether age-related asymmetry changes are affected by brain size, sex, and intelligence.

Methods:

The sample was obtained from the UK Biobank and included participants between 48 and 80 years of age (mean±SD: 62.1±7.2) without any neuropsychiatric conditions, cancer, or stroke. The T1-weighted brain images were processed using the CAT12 toolbox (https://neuro-jena.github.io/cat/) extracting 27 brain regions as per the LPBA40 atlas (https://www.loni.usc.edu/research/atlases). First, we calculated the left- and right-hemispheric volumes and then we calculated the asymmetry index (AI) as AI = (right - left) / (0.5 x [right + left]). Finally, we converted the AI into absolute values and conducted the statistical analyses testing (a) if there was a link between brain asymmetry and age and (b) if this link was affected by total intracranial volume (TIV), biological sex, and fluid intelligence. For all analyses, we used a Monte-Carlo simulation with 10,000 permutations to establish significance and controlling the family-wise error to correct for multiple comparisons.

Results:

We detected a significant positive correlation between asymmetry and age for the parahippocampal gyrus (r=0.10, p=0.002) and the putamen (r=0.08, p=0.032) indicating stronger asymmetries in older participants. In contrast, we detected a significant negative correlation between asymmetry and age in the cingulate gyrus (r=0.08, p=0.013) indicating stronger asymmetries in younger participants. TIV, biological sex, and fluid intelligence did not have a significant impact on the correlation between asymmetry and age.

Conclusions:

Out of the 27 regions examined, only three showed a significant link between asymmetry and age (for two regions the hemispheres became more different over time; for one region they became more similar). Thus, brain asymmetry seems to remain relatively stable over time for most of the brain, at least with respect to regional volumes. Future studies might benefit from exploring additional morphometric measures (e.g., cortical thickness), from conducting longitudinal analyses, as well as from including cognitive measures in various domains (e.g., working memory, attention, processing speed, verbal fluency, or visuospatial abilities) to investigate if age-related changes in brain asymmetry are linked to age-related changes in cognitive function.

Lifespan Development:

Aging 1

Modeling and Analysis Methods:

Segmentation and Parcellation

Neuroanatomy, Physiology, Metabolism and Neurotransmission:

Cortical Anatomy and Brain Mapping 2

Novel Imaging Acquisition Methods:

Anatomical MRI

Keywords:

ADULTS
Aging
MRI
NORMAL HUMAN
STRUCTURAL MRI
Other - Asymmetry

1|2Indicates the priority used for review

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Healthy subjects only or patients (note that patient studies may also involve healthy subjects):

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Was this research conducted in the United States?

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Were any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.

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Structural MRI

For human MRI, what field strength scanner do you use?

3.0T

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