Dedifferentiation of Functional Brain Activation Associated With Greater Visual Discrimination Accuracy in Middle-Aged and Older Adults.

Eric C Porges,Ronald A Cohen,Talia R Seider,Adam J Woods

doi:10.3389/fnagi.2021.651284

Abstract

Neural dedifferentiation refers to an age-related phenomenon whereby brain functions that are localized to specific, distinct, and differentiated brain areas in young adults become less so as people reach more advanced age. Older adults tend to exhibit greater spread of cortical activation on fMRI during cognitive processing compared to younger adults, with evidence that this occurs during visuoperceptual processing. Some age-related functional changes are considered compensatory, but whether dedifferentiation is compensatory is not clearly understood. The current study assessed dedifferentiation and visual discrimination performance during simultaneous match-to-sample tasks from the Visual Assessment Battery (VAB) among 40 healthy middle-aged and older adults using fMRI. Task-relevant regions of interest (ROIs) were created in the dorsal stream for discrimination of spatial location, the ventral stream for shape, and an area encompassing V5 for velocity. Dedifferentiation, or less specificity in functional activation, was associated with greater discrimination accuracy and more years of education. Secondary analyses showed that reduced functional activation in task-relevant ROIs was associated with faster discrimination speed. Age was unassociated with functional activation. Results suggest that dedifferentiation is compensatory. Lack of age effects suggest that other factors beyond age, such as cognitive or brain reserve, may better predict performance when considering cognitive skills that are relatively stable as adults age, such as visual discrimination.

Highlights

Advanced age is associated with loss of brain volume, in frontal regions, as well as a reduction in white matter integrity (Raz et al, 2005; Madden et al, 2012)
The current study examined whether age-associated dedifferentiation existed during visual discrimination tasks, and whether functional activation was related to performance
Forty healthy adults ages 51–91 were recruited from a larger dataset of community-dwelling adults enrolled in the Active Brain study, a University of Florida (UF) neuroimaging study aimed at investigating brain activity in healthy older adults

Summary

Introduction

Advanced age is associated with loss of brain volume, in frontal regions, as well as a reduction in white matter integrity (Raz et al, 2005; Madden et al, 2012). Functional changes have been reported, such as neural dedifferentiation. This refers to an age-related phenomenon whereby brain functions that are localized to specific, distinct, and differentiated brain areas in young adults become less so as people reach more advanced age. Dedifferentiation and Visual Discrimination in Aging more “face” regions when viewing places and more “place” regions when viewing faces (compared to younger adults), but there is increased functional activation in each of those areas in response to a greater variety of visual stimuli in older adults than in younger adults. Functional activity in the older brain is less specialized

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