Categorization of novel animals by patients with Alzheimer's disease and corticobasal degeneration.
We taught a novel animal category by rule-based and similarity-based processes to participants with Alzheimer's disease (AD), corticobasal degeneration (CBD), and healthy age-matched participants. Healthy participants successfully categorized by either process. AD patients' rule-based categorization was impaired, while their similarity-based categorization resembled that of healthy participants. Correlations of AD patients' performance with measures of executive functioning suggested a deficit in the cognitive resources necessary for engaging rule-based categorization. The contribution of limited executive resources to categorization difficulty in AD was further demonstrated in a second experiment in which features determining category membership were of lower salience. CBD patients were relatively impaired at similarity-based processing, suggesting that qualitatively distinct categorization processes can be selectively compromised in patients with focal neurodegenerative diseases. Moreover, AD patients' impaired categorization correlated with performance on a measure of semantic memory, implicating this categorization deficit in AD patients' semantic memory difficulty.
Koenig
Phyllis
P
Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-4283, USA. plkoenig@mail.med.upenn.edu
Smith
Edward E
EE
Moore
Peachie
P
Glosser
Guila
G
Grossman
Murray
M
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D000704:Analysis of Variance; D000818:Animals; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000503:physiopathology*; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology*; D012660:Semantics