Danae J. Lund

Date of Award

12-1-1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Abstract

Recently, there has been increased interest in the changes in neuropsychological functioning which are associated with normal aging. Understanding age differences in neuropsychological functioning is of particular importance in the discrimination of normal aging from the early onset of Alzheimer’s Disease or other age-associated dementia. Older adults have been observed to perform more poorly than younger adults on several auditory memory measures which are commonly included in neuropsychological batteries. Age associated declines on these measures have been reported even in the absence of dementia or other health concerns.

To date, explanations for these age differences have focused on a decline in cognitive processing efficiency. For example, older adults may have a diminished working memory capacity or a diminished working memory processing speed. However, another potential contributing factor to age differences in auditory memory performance may be subtle age associated degradation of the central auditory system. Age associated impairment has been widely reported on tests of both central and peripheral auditory processing. The purpose of the present investigation was to examine the degree to which auditory processing efficacy mediated age associated decline on auditorially presented measures of memory.

Twenty-eight independently living adults over sixty years of age and thirty-two adults between eighteen and thirty years of age were administered a battery of standardized memory and auditory tests which have been found to be sensitive to age. Tests of both peripheral and central auditory functioning were included in the battery. Peripheral auditory decline involves loss o f hearing sensitivity and reflects primarily cochlear involvement, while central auditory decline involves a loss of speech intelligibility and reflects primarily central nervous system dysfunction. The auditory battery included the Pure Tone Threshold, Speech Perception in Quiet, Speech Perception in Noise, Low Pass Filtered Speech, Time Compressed Speech, and the Synthetic Sentence Identification Test. Memory measures were all auditorially administered, and included the California Verbal Learning Test and the Logical Memory, Verbal Paired Associates, and Digit Span subtests of the Wechsler Memory Scale-Revised.

Age associated decline was observed on all auditory and memory measures. Age related deficits were especially apparent during the encoding stage of memory processing, which is consistent with the auditory processing hypothesis. Multiple regression analysis was then used in order to examine age differences in memory processing after age differences in auditory processing had been partialled out. Results indicated that in some instances, age no longer accounted for a significant portion of the variance in memory performance when auditory variables had been factored into the equation. In other instances, auditory variables greatly reduced the portion of the variance uniquely accounted for by age. Several auditory variables consistently emerged as significant predictors of memory performance, and these variables appeared to coincide with complaints commonly made by older individuals regarding their hearing, namely, that others often speak too softly, mumble, and speak too quickly.

Implications include the importance o f ruling out subtle sensory dysfunction in older individuals presenting with memory complaints. While older adults may be aware that they sometimes experience difficulty remembering auditorially presented information, they may attribute these lapses to impaired cognitive functioning rather than to a form of sensory dysfunction. These individuals may benefit from an audiological consultation for recommendations regarding the appropriateness of various auditory compensatory strategies.

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