Neural Correlates of Stroop Performance in Alzheimer's Disease: A FDG-PET Study

BACKGROUND/AIMS The Stroop test is commonly applied in elderly subjects for the evaluation of cognitive impairment related to Alzheimer's disease (AD) and related disorders. This study aimed to investigate the functional neural correlates of the Stroop performance in AD. METHODS In 136 probable AD patients and 54 cognitively normal elderly, a [(18)F]-fluorodeoxyglucose positron emission tomography scan and Stroop Color Word Test (SCWT) were performed. The correlations between the Stroop effect, which was measured by 6 different scoring methods, and regional cerebral glucose metabolism (rCMglc) were explored using a region-of-interest (ROI) approach and voxel-based analysis. RESULTS Among 6 Stroop interference measures, only 2 scores, including the SCWT color-word (CW) score, were significantly correlated with rCMglc of the dorsolateral prefrontal and anterior cingulate ROIs. Voxel-based analysis revealed significant positive correlations between SCWT CW scores and rCMglc in the inferior parietal lobule, middle temporal gyrus and middle frontal gyrus. Such correlations remained significant only in the less severe AD group. CONCLUSION In AD patients, the Stroop effect depends on the functional integrity of the prefrontal cortices. Some parietotemporal regions also appear to be responsible for the Stroop effect in AD individuals.