Moderating Effect of Cortical Thickness on BOLD Signal Variability Age-Related Changes.

Daiana R Pur,Sandrine De Ribaupierre,Roy A Eagleson,Anik De Ribaupierre,Nathalie Mella

doi:10.3389/fnagi.2019.00046

Daiana R Pur, Sandrine De Ribaupierre + Show 3 more

Open Access

https://doi.org/10.3389/fnagi.2019.00046

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Abstract

The time course of neuroanatomical structural and functional measures across the lifespan is commonly reported in association with aging. Blood oxygen-level dependent signal variability, estimated using the standard deviation of the signal, or “BOLDSD,” is an emerging metric of variability in neural processing, and has been shown to be positively correlated with cognitive flexibility. Generally, BOLDSD is reported to decrease with aging, and is thought to reflect age-related cognitive decline. Additionally, it is well established that normative aging is associated with structural changes in brain regions, and that these predict functional decline in various cognitive domains. Nevertheless, the interaction between alterations in cortical morphology and BOLDSD changes has not been modeled quantitatively. The objective of the current study was to investigate the influence of cortical morphology metrics [i.e., cortical thickness (CT), gray matter (GM) volume, and cortical area (CA)] on age-related BOLDSD changes by treating these cortical morphology metrics as possible physiological confounds using linear mixed models. We studied these metrics in 28 healthy older subjects scanned twice at approximately 2.5 years interval. Results show that BOLDSD is confounded by cortical morphology metrics. Respectively, changes in CT but not GM volume nor CA, show a significant interaction with BOLDSD alterations. Our study highlights that CT changes should be considered when evaluating BOLDSD alternations in the lifespan.

Highlights

Normal aging is associated with marked functional and structural neuroanatomical alterations in cortical thickness (CT), gyrification, cortical surface area (CA), gray (GM), and white matter volume (WM) (Salat et al, 2009; Thambisetty et al, 2010; McGinnis et al, 2011; Hogstrom et al, 2013)
Our study showed that CA and gray matter (GM) are highly correlated r = 0.904, p < 0.001 (95% Cl 0.901–0.908) and collinearity was suspected
Multiple Linear mixed effects models (LMMs) were utilized to assess the effect of neuroanatomical metrics CT, CA, and GM on BOLDSD age-related changes

Summary

Introduction

Normal aging is associated with marked functional and structural neuroanatomical alterations in cortical thickness (CT), gyrification, cortical surface area (CA), gray (GM), and white matter volume (WM) (Salat et al, 2009; Thambisetty et al, 2010; McGinnis et al, 2011; Hogstrom et al, 2013). Magnetic resonance imaging studies (MRI) show that the magnitude and rate of change of these cortical morphometry metrics is not constant across the cortex but rather it varies with age and brain region (Raz, 2005; Jiang et al, 2014; Storsve et al, 2014; Dotson et al, 2016), and is reported to accelerate with increasing age (Driscoll et al, 2009; Jiang et al, 2014). Functional magnetic resonance imaging (fMRI) studies, which rely on the blood oxygen level-dependent (BOLD) signal as a correlate of neuronal activity, report that changes in cortical morphology across adult lifespan impact the hemodynamic properties of the brain. Since aging is associated with significant neuroanatomical alterations, these should be considered when assessing function (i.e., cognitive ability) using the BOLD signal

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