Subcortical amyloid relates to cortical morphology in cognitively normal individuals
Amyloid (Aβ) brain deposition can occur in cognitively normal individuals and is associated with cortical volume abnormalities. Aβ-related volume changes are inconsistent across studies. Since volume is composed of surface area and thickness, the relative contribution of Aβ deposition on each of these metrics remains to be understood in cognitively normal individuals.
A group of 104 cognitively normal individuals underwent neuropsychological assessment, PiB-PET scan, and MRI acquisition. Surface-based cortical analyses were performed to investigate the effects of cortical and subcortical Aβ burden on cortical volume, thickness, and surface area. Mediation analyses were used to study the effect of thickness and surface area on Aβ-associated volume changes. We also investigated the relationships between structural metrics in clusters with abnormal morphology and regions underlying resting-state functional networks and cognitive performance.
Cortical Aβ was not associated with cortical morphology. Subcortical Aβ burden was associated with changes in cortical volume, thickness, and surface area. Aβ-associated volume changes were driven by cortical surface area with or without thickness but never by thickness alone. Aβ-associated changes overlapped greatly with regions from the default mode network and were associated with lower performance in visuospatial abilities, episodic memory, and working memory.
In cognitively normal individuals, subcortical Aβ is associated with cortical volume, and this effect was driven by surface area with or without thickness. Aβ-associated cortical changes were found in the default mode network and affected cognitive performance. Our findings demonstrate the importance of studying subcortical Aβ and cortical surface area in normal ageing.
KeywordsAmyloid beta Subcortical Default mode network Pittsburgh compound B Cognitive ageing
This work was funded by the Canadian Institutes of Health Research (no. MOP123376) and the Institute of Aging (no. IA0120269). SJ was supported by a Chercheur boursier senior award from the Fonds de recherche du Québec—Santé (FRQ-S).
Compliance with ethical standards
Conflict of interest
Christian Bocti declares investments at IMEKA. None of the other co-authors report having any conflicts of interests.
All research protocols were reviewed and in accordance with ethical standards. They were approved by the Centre de recherche de l’Institut universitaire de gériatrie de Montréal, the Montreal Neurological Institute, and the Hospital Research Ethics Boards.
All subjects gave their informed consent prior to their participation in the study.
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