This area of research is essential to understanding the basis of normal mental function so that we can investigate failing memory and cognitive function among the elderly.
Working memory. Working memory is the retention and manipulation of material over a short period of time. Tasks that are thought to tap working memory may involve multiple brain systems. Statistical analysis of brain imaging data has suggested that a brain system thought to be involved in long-term memory is also activated during working memory tasks.
Priming. Priming refers to changes in task performance simply as a result of a prior presentation without necessarily being aware of that prior experience. The neural basis of priming is still not well established. Using functional magnetic resonance imaging (fMRI), we found that some brain areas were differentially active during priming depending on whether or not the visual stimuli could be conceived as coherent three-dimensional structure as apposed to another type of structure. This suggests that the neural basis of priming differs with features of the stimuli.
Timing. We are studying how we learn and recall time intervals ranging from seconds to minutes. We demonstrated the effects of aging and the dopamine system on timing. Also, using a new methodology, we completed an fMRI study of timing in healthy young participants. Further studies in healthy and pathological aging are planned.
Neural representation of cognitive reserve. Cognitive reserve allows people to maintain function in the face of Alzheimer's disease pathology. Individuals with more cognitive reserve are thought have more efficient brain networks or to use new compensatory networks more effectively. In a positron emission tomography (PET) imaging study, we found a brain network whose relationship to measures of cognitive reserve differed in young and elderly subjects (see figure below). This network may be used by elders to compensate for the effects of aging on the brain.
Measures of cognitive reserve. We found that literacy level was a better predictor than education of decline in cognitive function over time. This suggests that in an ethnically diverse cohort, literacy level is a better proxy for cognitive reserve than education.
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|A covariance pattern ("brain network") noted in young and healthy elderly individuals. Correlation between expression of this network and measures of cognitive reserve were positive in the young adults and negative in the healthy elders. This suggests that the elders are using this network in a compensatory manner, perhaps to cope with the neural effects of aging.
Brain structure changes in normal aging. MRI studies have shown dramatic changes with aging in the brain's grey and white matter. We used a new approach to identify patterns of grey and white matter tissue density that reliably discriminated young and old individuals. Expression of these patterns predicted cognitive performance and may be an effective measure of "brain aging."
Using positron emission tomography to predict who will develop Alzheimer's disease (AD). PET imaging is currently not reliable for diagnosis or prognosis in AD. Stern and colleagues found that in individuals with mild cognitive impairment (MCI), a measure of patterns of blood flow in resting PET scans can predict who will show greater decline in neuropsychological test scores in the future. This method might be used clinically to predict whether a patient with memory problems will develop Alzheimer's disease.
Metacognition in Alzheimer's disease. Metacognition refers to our awareness of our cognitive capacities. Some patients with Alzheimer's disease are aware of their cognitive deficits while others are not. In order to understand why this occurs, we adapted a technique used to study metacognition in normal young adults. These techniques suggest that Alzheimer's disease patients with disordered awareness might have specific deficits in cognitive functions mediated by the right hemisphere.