Neural Dedifferentiation in the Aging Brain

Abstract

Many cognitive abilities decline with age even in the absence of detectable pathology. Recent evidence indicates that age-related neural dedifferentiation, operationalized in terms of neural selectivity, may contribute to this decline. We review here work exploring the relationship between neural dedifferentiation, cognition, and age. Compelling evidence for age effects on neural selectivity comes from both non-human animal and human research. However, current data suggest that age does not moderate the observed relationships between neural dedifferentiation and cognitive performance. We propose that functionally significant variance in measures of neural dedifferentiation reflects both age-dependent and age-independent factors. We further propose that the effects of age on neural dedifferentiation do not exclusively reflect detrimental consequences of aging.

Keywords: cognitive aging; differentiation; individual differences; neural selectivity.

Figure 1.. Example of category selective age-related dedifferentiation as indexed by fMRI BOLD activity.

(A) Participants are presented with exemplars of different perceptual categories (here, scenes and objects) that elicit category-selective activity in different regions of occipito-temporal cortex. (B) Age-related neural dedifferentiation takes the form of reduced category-selectivity – the difference between a region’s response to a preferred relative to a not-preferred stimulus – in older relative to young participants. (C) Three possible response patterns in category-selective cortex to preferred and non-preferred stimuli that could underlie the age-related neural dedifferentiation in B. Neural dedifferentiation can be driven by a reduction in a region’s response to its preferred stimulus (Attenuation), an increase in a region’s response to a non-preferred stimulus (Broadening), or a mixture of the two [48].