Neural Dedifferentiation in the Aging Brain

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. Research over the past two decades has significantly improved our understanding of the plethora of factors contributing to cognitive aging.We provide a selective review of studies investigating age differences in neural differentiation, as defined by measures of neural selectivity or specificity.The evidence indicates that neural differentiation decreases in healthy older adults and predicts performance across multiple cognitive domains in an age-invariant manner.Many factors likely contribute to age-related neural dedifferentiation, including age differences in neuromodulatory drive, the efficacy of inhibitory neurotransmission, response to task demands, and cumulative life experience.The current evidence raises the possibility that neural dedifferentiation does not exclusively reflect detrimental consequences of brain aging.