Effects of aging on speech sound discrimination in the Mongolian gerbil

The of this study was to examine the hypothesis that aging would adversely effect speech sound discrimination in the Mongolian gerbil, as assessed by behavioral techniques. The involved measuring difference limens (DLs) for frequency changes along three synthetic speech continua (vowel, liquid, stop-consonant) in 25 gerbils as a function of age up to 36 mo. Absolute thresholds were also measured in the aging gerbils to verify normal hearing. The indicated no adverse effects of aging on the DLs for any of the speech continua. Thus the was that "intrinsic" aging processes in the gerbil, considered apart from "extrinsic" insulting factors, are not detrimental to speech discrimination, at least under quiet conditions. The clinical implications for humans are that the deficits typically observed in elderly humans for speech sound discrimination may be insult-related, and not the result of normal aging processes.