The Role of Sensory Decline In Cognitive Aging

University Of Michigan At Ann Arbor, Ann Arbor MI

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Abstract

It is well documented that older adults experience both sensory and cognitive decline and that sensory function and cognitive function are correlated in older adults. A large part of this correlation appears to be due to a third factor relating sensory function and cognitive function, most likely neurobiological change. This view has been called the common-cause hypothesis in the literature. However, there may be other ways that sensory decline can affect cognitive performance in older adults that operate in addition to the common cause. This proposal examines the "direct-cause" hypothesis that cognitive performance is directly impaired by poor sensory function in tasks where perceptual demands are high. In particular, stimuli in many tasks are frequently familiar and well-learned verbal items. Because these are well-learned and often occur in a context that provides support for perceptual processing, reduced sensory acuity may not impact cognitive performance. However, stimuli that are not well-learned will rely much more on initial "bottom-up" sensory processing. In these cases, significant portions of the effects due to aging may be explained by sensory function. The direct-cause hypothesis will be tested using two different analytical approaches. In the first, a pre-existing data set containing measures of sensory function (visual acuity, contrast sensitivity, auditory acuity) and measures of cognition that used familiar (i.e., verbal) stimuli and that used unfamiliar (i.e., visuospatial) stimuli will be analyzed using regression techniques. The prediction is that more age-related variance will be explained by contrast sensitivity for the visuospatial tasks than the verbal tasks. In the second approach, auditory discriminability will be experimentally manipulated in a dual- task paradigm. Perceptual identification time has been shown to be experimentally manipulated in a dual-task costs. By manipulating the perceptual difficulty of the task, age differences in dual-task cost should vary accordingly. In one condition, the auditory stimuli will be pure tones, in te other condition the auditory stimuli will be common names. The prediction is that age differences will be smaller for the condition using familiar common names. This work would add to our understanding of the ways by which sensory function can affect cognitive function in older adults and has theoretical and applied implications.