Pitch perception in individuals with sensorineural hearing loss with and without dead regions

Abstract

It has been suspected that a pure tone might be perceived as noise like when the tone produces maximum excitation in a region of the cochlea where there is extensive or complete loss of inner hair cell (IHC) and /or neural function which is referred to as a dead region (DR). It is defined as region in the cochlea where IHCs and /or neurons are functioning so poorly that a tone producing peak vibration in that region is detected by off place listening (i.e. the tone is detected at a place where the amount of basilar membrane vibration is lower but IHCs and neurons are functioning more effectively). In this study total 17 sensorineural hearing loss individuals with and without dead region were taken. They were divided into two groups- subjects having sensorineural hearing loss with dead region and without dead region. For detection of dead regions psychophysical tuning curves (PTCs) was established using a procedure which is similar to the physiological determination of a tuning curve on the basilar membrane or in the auditory nerve. TEN (Threshold-Equalizing Noise) test was also used which is relatively fast and simple test. If the subjects had dead region or not then pitch matching experiment was carried out. For the pitch matching task subjects were asked to match the perceived pitch of a variable pure tone with that of another pure tone that was fixed in frequency. The results reveal that pitch perception in individuals with sensorineural hearing loss with dead region is different than in those individuals having sensorineural hearing loss without dead region. The result also shows that if sensorineural hearing loss is accompanied with dead region (DR) then there is broader auditory filter and hence pitch matching is difficult.