The Efficacy of Using Filtered Dichotic Words to Detect Subtle Auditory Processing Issues In Young Adults
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Date
2015-05
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The Ohio State University
Abstract
An auditory processing disorder (APD) is a perceptual issue affecting the way the central auditory nervous system understands and makes use of auditory information. APD is associated with young children and aging adults, and is associated with extreme difficulty understanding speech in complex listening environments. Clinical experience tells us adults between the ages of 18 and 59 years also experience listening difficulties consistent with APD, despite normal hearing test results. A popular commercial test battery of APD in adults, the SCAN-3:A, has been criticized for its lack of sensitivity for adults who experience listening difficulties consistent with APD. Dichotic listening has been shown to be sensitive to APD in both children and older adults. In an effort to increase the sensitivity of dichotic listening to the complaints of otherwise normal hearing adults, Lamoreau (2012) examined filtered dichotic word recognition in a group of adults with subjective listening complaints. Results from her study were promising, in that performance on the filtered dichotic words differentiated between control subjects and experimental subjects with borderline abnormal performance on the SCAN-3:A. The purpose of the present study was to extend the results of the Lamoreau study by recruiting additional subjects. Twenty-three right-handed young adults with normal hearing were separated into two groups (control and experimental) based on their scores from two auditory processing questionnaires. All subjects were tested with pure tone audiometry to confirm thresholds within normal limits. Four subtests of the SCAN-3:A were administered: 1) Auditory Figure Ground, 2) Filtered Words, 3) Competing Words, and 4) Competing Sentences. Following the SCAN-3:A, the dichotic word task was administered in both unfiltered and filtered conditions. The dichotic words were filtered with a center frequency of 1500 Hz, a low-pass cutoff of 2521 Hz, and a high-pass cutoff of 892 Hz. Dichotic word recognition was also measured in three response conditions: free recall, directed right, and directed left. The unfiltered condition preceded the filtered condition, and the free recall response condition preceded the directed recall conditions. Results showed poorer performance in speech recognition for filtered dichotic words relative to the unfiltered dichotic words. Overall, there was not a significant difference in performance between groups, but there were intriguing findings for four individuals from the experimental group. These four subjects with subjective listening complaints performed normally on the SCAN-3:A, but had abnormal results for the filtered dichotic words. The abnormal performance on the filtered dichotic words leads us to believe the task may be sensitive to subjective listening complaints of young adults with normal hearing. In the future, changes will be made to the inclusion criteria to reduce variability in subjects and to the procedure to lighten the cognitive load of the directed recall condition (repeat directed ear only) in order to show a more accurate representation of performance and ear advantage.
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Keywords
auditory processing, complex listening environments, young adults, dichotic words