Auditory stimulus intensity and reaction time in listeners with longstanding sensorineural hearing loss.

Abstract

This study examined relationships among sound level, subjective loudness, and reaction time in listeners with longstanding sensorineural hearing loss and loudness recruitment. A simple reaction-time test was performed by 10 hearing-impaired (HI) subjects with varying degrees of recruitment and by 10 normal-hearing (NH) control subjects. Both groups listened to 0.5 kHz tones presented at a soft level, representing the soft endpoint of a subject's functional dynamic range, and a loud level representing the loud endpoint. In one condition, the loudness level of stimuli within a block was fixed, and hence predictable; in another it varied randomly within a block between loud and soft, adding uncertainty to the simple reaction time task. A test with exactly the same design but using visual stimuli was also performed. 1) In general, the HI subjects responded to auditory stimuli with normal or near-normal mean reaction times when stimulus loudness was predictable. 2) Introduction of uncertainty disrupted the reaction time performance of some, but not all, of the HI subjects. 3) Both the HI and the NH subjects responded more quickly to loud tones than to soft ones. Under the predictable loudness condition the magnitude of this "speed up" was nearly identical for the two groups despite the fact that the HI group had, on average, only half the physical dynamic range of the NH group. 4) Visual reaction-time performance was equivalent between the HI and NH groups in all important respects. Despite long-term auditory deficits, HI subjects' ability to respond quickly to simple auditory signals is not substantially impaired, particularly when listening under predictable loudness conditions. Although physical soft-loud ranges will generally be narrower than normal for HI subjects, their reaction time performance at the endpoints of that range is likely to be near normal.