Language impairment is a common symptom of Alzheimer disease (AD), and is thought to be related to semantic processing. This study examines the contribution of another process, namely visual perception, on measures of confrontation naming and semantic association abilities in persons with probable AD.
Twenty individuals with probable mild-moderate Alzheimer disease and 20 age-matched controls completed a battery of neuropsychologic measures assessing visual perception, naming, and semantic association ability. Visual discrimination tasks that varied in the degree to which they likely accessed stored structural representations were used to gauge whether structural processing deficits could account for deficits in naming and in semantic association in AD.
Visual discrimination abilities of nameable objects in AD strongly predicted performance on both picture naming and semantic association ability, but lacked the same predictive value for controls. Although impaired, performance on visual discrimination tests of abstract shapes and novel faces showed no significant relationship with picture naming and semantic association. These results provide additional evidence to support that structural processing deficits exist in AD, and may contribute to object recognition and naming deficits.
Our findings suggest that there is a common deficit in discrimination of pictures using nameable objects, picture naming, and semantic association of pictures in AD. Disturbances in structural processing of pictured items may be associated with lexical-semantic impairment in AD, owing to degraded internal storage of structural knowledge.
*Department of Communication Sciences and Disorders
∥Department of Psychiatry, University of Cincinnati, Cincinnati, OH
†Department of Neurology
¶Department of Speech, Language, and Hearing Sciences
**Department of Clinical and Health Psychology, University of Florida
‡Malcom Randall VA Brain Rehabilitation Research Center Gainesville, FL
§Department of Communicative Disorders and Sciences, San Jose State University
††Department of Anatomy and Neurobiology, University of Kentucky, Lexington, Kentucky
Supported by the Indiana Alzheimer's Disease Center (P30 AG10133), the National Institutes of Health (R01 MH063817, T32 DC008768, K23 DC010197), and the German Foundation for Science (DFG, ME 3161/2-1). Reprints: Stacy M. Harnish, PhD, CCC-SLP, Malcom Randall VAMC, Brain Rehabilitation Research Center (BRRC) 151-A, 1601 SW Archer Rd, Gainesville, FL 32608 (e-mail: firstname.lastname@example.org).
Received December 9, 2009
Accepted May 2, 2010