Neural Correlates of Executive Dysfunction in Prodromal and Manifest Alzheimer’s Disease

Executive function is frequently impaired in patients with Alzheimer’s disease (AD) and its prodromal stage, and can be assessed using the Trail-Making Test (TMT). We aimed to elicit the neural and cognitive correlates of TMT subtests using positron emission tomography with 18-fluoro-D-deoxy-glucose, and neuropsychological testing in 20 patients with prodromal or manifest AD as well as 14 controls. TMT-A correlated with glucose metabolism in the left middle frontal cortex, TMT-B performance correlated with the metabolism in the right middle frontal cortex and the right precentral gyrus, and TMT-Q performance correlated with metabolism in the right middle frontal cortex. The present findings reveal functional imaging evidence that executive dysfunction in AD as measured by TMT is frontal lobe mediated.