Dissociative effects of age on neural differentiation at the category and item level.

Cognitive aging is associated with a decline in the selectivity of the neural responses within cortical regions that respond differentially to distinct perceptual categories (age-related neural dedifferentiation). However, prior research indicates that while scene-related selectivity is reduced in older age and is correlated with cognitive performance independently of age, selectivity for object stimuli is typically not moderated by age or memory performance. Here, we demonstrate that neural dedifferentiation is evident for both scene and object exemplars when it is defined in terms of the specificity of neural representations at the level of individual exemplars. These findings suggest that neural selectivity metrics for stimulus categories and for individual stimulus items depend on different neural mechanisms.