Title

Electrophysiological Measures of Gap Detection Threshold in Younger and Older Normal Hearing Adults

Date of Completion

January 2011

Keywords

Health Sciences, Audiology|Gerontology

Degree

Ph.D.

Abstract

The ability to detect small silent intervals within a carrier signal, such as white noise, is an important listening skill. This gap detection ability is correlated with normal speech understanding, as well as understanding speech in difficult listening environments. Conflicting results are seen in the literature investigating gap detection ability in older adults, but it is suggested that poor gap detection may be related to some older adults' complaints of difficulty understanding speech in background noise. Typically, gap detection is evaluated using a behavioral technique and each individual being tested must respond to the stimuli in some way. Recent research has shown that it is possible to evaluate gap detection using evoked potentials. Specifically, the N1-P2 response can be elicited by gaps as short as 5 msec. ^ Subject groups in this study consisted of 11 younger adults (age 19–26 years) and 11 older adults (age 60–82 years). All subjects demonstrated normal peripheral hearing. A behavioral gap detection threshold (BGDT) and an electrophysiologic gap detection threshold (EGDT) were determined for each subject. ^ Results showed that there was no significant difference between BGDT and EGDT in either subject group, however these two measures were not correlated. The older adults did show significantly longer BGDT and EGDT when compared to the younger adults. Pure tone thresholds were correlated with both BGDT and EGDT, however they were not considered good predictors of either measure. Older adults also showed delayed P2 latency in recordings at EGDT compared to the young adults with no change in N1 latency, N1 amplitude or P2 amplitude. ^ Overall, this study found that temporal resolution can be evaluated using evoked potentials measures and that electrophysiological gap detection threshold is not significantly different from behavioral gap detection threshold in normal hearing adults, both younger and older. Older adults did demonstrate poorer temporal resolution than younger adults and exhibited morphological differences in their evoked potential recordings. Future research in this area should include individuals with central auditory lesions and subjects with sensorineural hearing loss in an effort to establish sensitivity and specificity data. ^