Our group has now published four studies demonstrating age-related changes in neural representations in human visual cortex using functional MRI. In our first study, we showed that the neural activity patterns elicited by faces, places, and words were significantly more distinctive in young adults than in old adults (Park et al., 2004 ). Specifically, in young adults, activity in the so-called fusiform face area (FFA) was more selective to faces, activity in the parahippocampal place area (PPA) was more selective to places, and activity in the visual word form area (VWFA) was more selective to words:
Both of these studies focused on age differences in average regional activation. However, these measures may not capture information encoded across multiple voxels within a region. Patterns of activation that cannot be discriminated by univariate analysis may nevertheless be discriminable by multivariate techniques. We therefore recently used multi-voxel pattern analysis (MVPA) to measure age differences in the distinctiveness of distributed patterns of neural activation evoked by different categories of visual images. Neural activation patterns within the ventral visual cortex were still significantly less distinct in older vs. younger adults in two separate samples, even when analyzed using a multivariate approach. (Carp et al., 2011 ).
A central challenge in the study of healthy aging is to identify factors that distinguish those who age gracefully from those who do not, because doing so could shed light on the underlying causes of age-related declines and how best to address them. We recently discovered that neural distinctiveness might be an important factor. Fluid processing ability is known to decline with age and we showed that individual differences in neural distinctiveness predict performance on a range of fluid processing tasks in older adults (Park et al., 2010 ). In fact, neural distinctiveness accounted for 30% of the variance in behavioral performance, despite the fact that neural distinctiveness was measured in visual cortex using simple visual tasks while the fluid processing tasks required far more general types of cognitive processing: