Corticolimbic interactions associated with performance on a short-term memory task are modified by age

Aging has been associated with a decline in memory abilities dependent on h ippocampal processing. We investigated whether the functional interactions between the hippocampus and related cortical areas were modified by age. Yo ung and old subjects' brain activity was measured using positron emission t omography (PET) while they performed a short-term memory task (delayed visu al discrimination) in which they determined which of two successively prese nted sine-wave gratings had the highest spatial frequency. Behavioral perfo rmance was equal for the two groups. Partial least squares (PLS) analysis o f PET images identified a hippocampal voxel whose activity was similarly co rrelated with performance across groups. Using this voxel as a seed, a seco nd PLS analysis identified cortical regions functionally connected to the h ippocampus. Quantification of the neural interactions with structural equat ion modeling suggested that a different hippocampal network supported perfo rmance in the elderly. Unlike the neural network engaged by the young, whic h included prefrontal cortex Brodmann's area (BA) 10, fusiform gyrus, and p osterior cingulate gyrus, the network recruited by the old included more an terior areas, i.e., dorsolateral prefrontal cortex (BA 9/46), middle cingul ate gyrus, and caudate nucleus. Recruitment of a distinct corticolimbic net work for visual memory in the elderly suggests that age-related neurobiolog ical deterioration not only results in focal changes but also in the modifi cation of large-scale network operations.