Adult Age Differences in Bottom-Up and Top-Down Influences on Auditory Laterality in Dichotic Listening.

Research Area: Research Year: 2010
Type of Publication: Poster presentation Keywords: Primary ATTENTION Development and aging Secondary ATTENTION Auditory
Authors: Passow, Susanne; Westerhausen, Rene; Wartenburger, I.; Hugdahl, Kenneth; Heekeren, H.R.; Lindenberger, U.; Li, S.-C.
ISSN 1096-8857
The right-ear advantage (REA), indicating superiority of the left hemisphere in speech processing, can be observed during verbal dichotic listening (e.g. Kimura, 1961). Recent studies with young adults focused on the interaction between bottom-up and top-down processes in affecting REA (e.g. Westerhausen et al., 2009). Initial evidence suggests that normal aging affects top-down attentional control of the REA. We investigated how normal aging alters (i) the interaction between bottom-up and top-down processes and (ii) lateralization of auditory processing. Twenty-four younger and 25 older adults were screened for their hearing acuity. Bottom-up stimulus characteristics were manipulated by gradually varying the inter-aural intensity differences. The degree of top-down modulation was manipulated by forcing attention to the right ear (FR), the left ear (FL), or none of the two ears (NF). The results of the behavioral study indicate: (i) bottom-up and top-down processes differ with age, as reflected in the significant four-way Attention x Ear x Intensity x Age interaction (epsilon=0.41, eta-squared=0.01); (ii) older adults’ performance for a given ear depends more on inter-aural intensity differences (Intensity x Ear: epsilon=0.28, eta-squared=0.95) than younger adults’ performance (Intensity x Ear: epsilon=0.23, eta-squared=0.71), indicating their reduced ability in exerting top-down control; (iii) relative to younger (RE>LE, Cohen’s d=0.95) the REA is weakened in older adults (RE>LE, n.s.). These behavioral results are in line with evidence on senescent decline in attentional control and on alterations in hemispheric asymmetry during speech processing (Bellis et al., 2000). The follow-up EEG experiment will investigate neurophysiological correlates of these age-related differences.
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