Binaural Pitch Fusion in Children With Normal Hearing, Hearing Aids, and Cochlear Implants

Abstract

Objectives: Binaural pitch fusion is the perceptual integration of stimuli that evoke different pitches between the ears into a single auditory image. Adults who use hearing aids (HAs) or cochlear implants (CIs) often experience abnormally broad binaural pitch fusion, such that sounds differing in pitch by as much as 3 to 4 octaves are fused across ears, leading to spectral averaging and speech perception interference. The main goal of this study was to measure binaural pitch fusion in children with different hearing device combinations and compare results across groups and with adults. A second goal was to examine the relationship of binaural pitch fusion to interaural pitch differences or pitch match range, a measure of sequential pitch discriminability. Design: Binaural pitch fusion was measured in children between the ages of 6.1 and 11.1 years with bilateral HAs (n = 9), bimodal CI (n = 10), bilateral CIs (n = 17), as well as normal-hearing (NH) children (n = 21). Depending on device combination, stimuli were pure tones or electric pulse trains delivered to individual electrodes. Fusion ranges were measured using simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus to find the range that fused with the reference stimulus. Interaural pitch match functions were measured using sequential presentation of reference and comparison stimuli, and varying the comparison stimulus to find the pitch match center and range. Results: Children with bilateral HAs had significantly broader binaural pitch fusion than children with NH, bimodal CI, or bilateral CIs. Children with NH and bilateral HAs, but not children with bimodal or bilateral CIs, had significantly broader fusion than adults with the same hearing status and device configuration. In children with bilateral CIs, fusion range was correlated with several variables that were also correlated with each other: pure-tone average in the second implanted ear before CI, and duration of prior bilateral HA, bimodal CI, or bilateral CI experience. No relationship was observed between fusion range and pitch match differences or range. Conclusions: The findings suggest that binaural pitch fusion is still developing in this age range and depends on hearing device combination but not on interaural pitch differences or discriminability.

Frequency Fitting Optimization Using Evolutionary Algorithm in Cochlear Implant Users with Bimodal Binaural Hearing

“…Finally, fitting based on the Greenwood map does not improve the binaural fusion in comparison to the default CI settings since complex central processing adaptations seem to modify the binaural interactions. In patients with bimodal binaural hearing or bilateral CI, two notes separated as far as three or four octaves presented simultaneously to both ears can be perceived with a similar pitch [ 20 , 21 ]. The extent of these alterations depends on many interconnected factors, such as ipsi- and contralateral auditory performances (i.e., speech discrimination, pitch resolution) and the hearing deprivation period [ 20 , 21 ].…”

“…With time and training, a tolerance to the shift between the electric and acoustic stimuli in terms of temporal and spatial coding appears [ 18 ]. In many implantees, a perceptual fusion is observed for two sounds with very different pitches presented simultaneously to both ears [ 20 , 21 ].…”

Participation of Acoustic and Electric Hearing in Perceiving Musical Sounds

“…Negative interference of CI on HA performances highlights the difficulty of finding the best possible match between acoustic and electric hearing inputs in binaural patients ( Keilmann et al, 2009 ). Recent studies on bimodal pitch perception offer another argument for the poor performance in classifying ascending and descending notes ( Hartling et al, 2020 ; Oh and Reiss, 2020 ). In patients with a hearing loss rehabilitated by HA or CI, a broad binaural pitch fusion is generally observed ( Hartling et al, 2020 ; Oh and Reiss, 2020 ).…”

“…Recent studies on bimodal pitch perception offer another argument for the poor performance in classifying ascending and descending notes ( Hartling et al, 2020 ; Oh and Reiss, 2020 ). In patients with a hearing loss rehabilitated by HA or CI, a broad binaural pitch fusion is generally observed ( Hartling et al, 2020 ; Oh and Reiss, 2020 ). Sounds differing in pitch by as much as three to four octaves are perceptually integrated across ears.…”

“…Sounds differing in pitch by as much as three to four octaves are perceptually integrated across ears. This phenomenon is subject to great inter individual variability both in adults ( Oh and Reiss, 2020 ) and children ( Hartling et al, 2020 ), depending on the mode of rehabilitation, the degree of loss and the duration of hearing deprivation. This phenomenon can mask the interval between the two presented notes by reducing the frequency resolution of the ear with a HA to the level of the contralateral CI in bimodal patients.…”