A growing literature has suggested that healthy aging is associated with disturbances in both DA and PFC function, and with cognitive impairments. However, despite accumulating evidence about these age-related cognitive and neurobiological changes, there is still little understanding of whether or how they are associated. Thus, CCP research is geared at understanding the potential functional significance of PFC and/or dopamine disturbances in healthy aging. Specifically, based on computational modeling work, we have hypothesized that healthy aging may involve a disturbance in cognitive control, which reflects a disturbance in context processing and PFC function. Consistent with this hypothesis, we have recently found in a large multi-site study that healthy older adults display specific deficits in the ability to represent and use context information to guide behavior (Braver, Barch et al., 2001).
Our current work has followed up on these projects with new behavioral and neuroimaging studies. In this work, we have found clear support for our prediction that healthy older adults show context processing impairments, and that these are amplified by both further advancing age and DAT (Braver, Barch et al., submitted). Moreover, in an fMRI study with healthy young and old adults, we found that older adults failed to increase activity in DL-PFC in relation to increased context processing demand. Taken together, these results suggest a tight link between DL-PFC activity and cognitive control impairment related to aging. Future studies will examine whether older adults show evidence of a bias towards a reactive rather than proactive mode of control in difficult cognitive tasks. We have already begun such efforts in the domain of categorization (Racine et al., submitted).