Asymmetric Differences in the Gray Matter Volume and Functional Connections of the Amygdala Are Associated With Clinical Manifestations of Alzheimer’s Disease

Abstract

Objective Asymmetry is a subtle but pervasive aspect of the human brain, which may be altered in several neuropsychiatric conditions. Magnetic resonance imaging (MRI) studies have reported that cerebral structural asymmetries are altered in Alzheimer’s disease (AD), but most of these studies were conducted at the region-of-interest level. At the functional level, there are few reports of resting-state functional asymmetries based on functional MRI. In this study, we investigated lateral differences in structural volumes and strengths of functional connectivity between individuals with AD and healthy controls (HCs) at the voxel level. Methods Forty-eight patients with AD and 32 matched HCs were assessed. An analysis of voxel-based morphometry (VBM) of gray matter volume was performed at the whole-brain level to explore anatomical cerebral asymmetries in AD. We then performed a seed-to-whole-brain functional connectivity (FC) analysis to reveal FC asymmetries in AD. An asymmetry index (AI) was used to measure these changes, and the relationship between the structural and functional AIs and the clinical symptoms of AD was explored. Results A VBM analysis revealed a rightward and a leftward lateralization in the amygdala and the thalamus, respectively, in patients with AD. FC between the amygdala and the precuneus showed a rightward lateralization in AD, which was the opposite of the lateralization in the HCs. The asymmetric changes in structure and function were associated with disease severity and functional impairment in AD. Conclusion Our study highlights the value of considering asymmetries in the amygdala and the thalamus in clinical evaluations and their relevance to clinical measures.

Butyrate ameliorates quinolinic acid–induced cognitive decline in obesity models

“…In the present study, the cortical reductions were sometimes observed only in 1 hemisphere. The prevalence of asymmetrical cerebral alterations has been extensively documented in the brains of patients with AD ( 52 ), schizophrenia ( 53 ), autism ( 54 ), anxiety disorders ( 55 ), or even type II diabetes ( 56 ). In the present study, GMV was reduced in the right temporal lobe of patients with obesity.…”

Machine Learning Workflow to Explain Black-Box Models for Early Alzheimer’s Disease Classification Evaluated for Multiple Datasets

“…This results in 152 MRI features (49 sums, 49 differences, 49 ratios, and 5 unpaired features). Brain asymmetry was previously associated with AD [47][48][49][50]. Equation 2 shows that differences were calculated by subtracting the right from the left volume similar to [48], where the cortical thickness was used instead of volumetric features…”

“…Those features describe the asymmetry of both hemispheres. Brain asymmetry measurements were associated with AD [47][48][49][50] and were also successfully applied for ML models in this field [75].…”

Machine Learning Workflow to Explain Black-box Models for Early Alzheimer's Disease Classification Evaluated for Multiple Datasets

“…This results in 152 MRI features (49 sums, 49 differences, 49 ratios, and five unpaired features). Brain asymmetry was previously associated with AD [47][48][49][50]. Equation 2 shows that differences were calculated by subtracting the right from the left volume similar to [48], where the cortical thickness was used instead of volumetric features.…”