HEARING, PSYCHOPHYSICS, AND COCHLEAR
IMPLANTATION: EXPERIENCES OF OLDER INDIVIDUALS
WITH MILD SLOPING TO PROFOUND SENSORY HEARING
LOSS
Authors: Gifford René , Dorman Michael , Brown Chris , Spahr Anthony 
Published: May 2021

In a previous paper we reported the frequency selectivity, temporal resolution, nonlinear cochlear processing, and speech recognition in quiet and in noise for 5 listeners with normal hearing (mean age 24.2 years) and 17 older listeners (mean age 68.5
years) with bilateral, mild sloping to profound sensory hearing loss (Gifford et al., 2007). Since that report, 2 additional participants with hearing loss completed experimentation for a total of 19 listeners. Of the 19 with hearing loss, 16 ultimately received a cochlear implant. The purpose of the current study was to provide information on the pre-operative psychophysical
characteristics of low-frequency hearing and speech recognition abilities, and on the resultant postoperative speech recognition
and associated benefit from cochlear implantation. The current preoperative data for the 16 listeners receiving cochlear implants
demonstrate: 1) reduced or absent nonlinear cochlear processing at 500 Hz, 2) impaired frequency selectivity at 500 Hz, 3) normal temporal resolution at low modulation rates for a 500-Hz carrier, 4) poor speech recognition in a modulated background,
and 5) highly variable speech recognition (from 0 to over 60% correct) for monosyllables in the bilaterally aided condition. As
reported previously, measures of auditory function were not significantly correlated with pre- or post-operative speech recognition – with the exception of nonlinear cochlear processing and preoperative sentence recognition in quiet (p=0.008) and at
+10 dB SNR (p=0.007). These correlations, however, were driven by the data obtained from two listeners who had the highest
degree of nonlinearity and preoperative sentence recognition. All estimates of postoperative speech recognition performance
were significantly higher than preoperative estimates for both the ear that was implanted (p<0.001) as well as for the best-aided
condition (p<0.001). It can be concluded that older individuals with mild sloping to profound sensory hearing loss have very
little to no residual nonlinear cochlear function, resulting in impaired frequency selectivity as well as poor speech recognition
in modulated noise. These same individuals exhibit highly significant improvement in speech recognition in both quiet and
noise following cochlear implantation. For older individuals with mild to profound sensorineural hearing loss who have difficulty in speech recognition with appropriately fitted hearing aids, there is little to lose in terms of psychoacoustic processing
in the low-frequency region and much to gain with respect to speech recognition and overall communication benefit. These
data further support the need to consider factors beyond the audiogram in determining cochlear implant candidacy, as older individuals with relatively good low-frequency hearing may exhibit vastly different speech perception abilities – illustrating
the point that signal audibility is not a reliable predictor of performance on supra-threshold tasks such as speech recognition.