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Amnestic mild cognitive impairment (aMCI) represents a high-risk factor for Alzheimer's disease (AD) and is characterized by a selective decline in episodic memory. Although by definition aMCI is not associated with impaired verbal fluency performance, we examined relative differences between fluency tasks because AD is characterized by poorer semantic than phonemic fluency. Phonemic and semantic fluency trials were administered to 46 healthy controls, 33 patients with aMCI, and 33 patients with AD. Results revealed a progressive advantage (controls > aMCI > AD) in semantic, relative to phonemic fluency. Difference scores between tasks distinguished each group from the others with medium to large effect sizes (d) ranging from 0.49 to 1.07. Semantic fluency relies more on semantic associations between category exemplars than does phonemic fluency. This aMCI fluency pattern reflects degradation of semantic networks demonstrating that initial neuropathology may extend beyond known early changes in hippocampal regions. (JINS, 2006, 12, 570–574.)The data were collected in accordance with the guidelines of the Helsinki Declaration and approved by the Research Ethics and Scientific Review Committee of Baycrest Centre. This is an original submission. Portions of these data were presented at the annual meeting of the International Neuropsychological Society, February 2005, St. Louis, Missouri. There is no conflict of interest.
Murphy et al. (Tue,) studied this question.