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March 1989

Divided Attention, as Measured by Dichotic Speech Performance, in Dementia of the Alzheimer Type

Author Affiliations

From the Laboratory of Neurosciences, National Institute on Aging (Drs Grady and Rapoport); Audiology Department (Ms Grimes) and Radiology Department (Dr Patronas), Clinical Center, National Institutes of Health; Clinical Neuropharmacology Branch, National Institute of Mental Health (Dr Sunderland); and the Experimental Therapeutics Branch, National Institute of Neurological Diseases and Stroke (Dr Foster), Bethesda, Md. Dr Foster is currently with the Department of Neurology, University of Michigan, Ann Arbor. Ms Grimes is currently with the Hearing Society for the Bay Area Inc, San Francisco.

Arch Neurol. 1989;46(3):317-320. doi:10.1001/archneur.1989.00520390083021

• To determine if impaired dichotic performance in patients with dementia of the Alzheimer type is due to the inability to divide attention or the inability to perceive degraded auditory stimuli, we measured performance on tasks of both dichotic and degraded monotic speech materials. We also examined whether perception of degraded speech stimuli presented monaurally is related to abnormalities of temporal lobe anatomy and physiology, as we have shown for dichotic performance. Although the patients were impaired on both dichotic and monotic tests, significantly greater impairment was seen on the dichotic test. Our earlier finding of a significant relation between dichotic performance and measures of anterior temporal lobe atrophy and reduced glucose metabolism was replicated, but no significant relation was found between monotic tests and measures of temporal lobe integrity. We conclude that the inability to divide attention, rather than abnormal processing of degraded stimuli per se, is reflected in poor dichotic performance in patients with dementia of the Alzheimer type, and that dichotic performance, unlike degraded monotic perception, depends directly on the integrity of temporal cortex in these patients.