2019 Conference on Implantable Auditory Prostheses

14-19 July 2019

Granlibakken, Lake Tahoe

Page 63

P36: INTERAURAL PITCH DISCRIMINATION IN CHILDREN WITH NORMAL HEARING,

HEARING AIDS, AND COCHLEAR IMPLANTS

Morgan Eddolls, Lina Reiss, Yonghee Oh, Curtis Hartling,

Alicia Johnson, Bess Glickman, Germaine Stark, Jennifer Ruiz

Oregon Health and Science University, Portland, OR, USA

Children with hearing loss potentially have central auditory processing abilities that differ from

their normal-hearing (NH) peers due to disruption of auditory input and/or abnormal stimulation

from hearing devices during development. Recent data suggests that hearing device

combination affects the development of binaural pitch fusion, which determines the range of

pitch differences over which dichotic stimuli are fused. Hearing device combination may affect

other abilities, such as interaural pitch discrimination. In this study, we measured interaural pitch

match functions in 25 NH, 10 hearing aid (HA), 11 bimodal cochlear implant (CI), and 18

bilateral CI children ranging in age from 6 to 10 years old.

A 2-interval, 2-alternative forced choice method of constant stimuli procedure was used to

measure pitch match functions. Depending on device combination, acoustic tones were

presented through headphones and/or electric pulse trains were presented to single electrodes.

In each trial, the reference ear was stimulated with a fixed stimulus (frequency or electrode), and

the contralateral, comparison ear stimulus was stimulated sequentially and varied in frequency

or electrode. The child was asked to choose which of the two stimuli sounded higher in pitch,

and a pitch match function was generated over several trials as a function of contralateral

stimulus.

Successful completion of the task was defined as being able to bracket the pitch match, i.e.

consistently rank some comparison stimuli as lower in pitch and another set of stimuli as higher

in pitch than the reference stimulus. Overall, in the first year, 96% of NH children, 70% of HA

children, 33.3% of bimodal CI children, and 50% of bilateral CI children were able to complete

the task. For those who completed the task, interaural pitch match discrimination ability was

measured as the pitch match range between the 25%-75% points of the pitch match function;

pitch match range is a measure of the steepness of the function slope, with narrow ranges

indicating steep slopes and wide ranges indicating shallow slopes and poor interaural pitch

discrimination. NH children had narrower pitch match ranges compared to the hearing-impaired

groups. When results were compared with data collected previously in equivalent adult groups,

NH children had significantly broader pitch match ranges than NH adults. No other differences

were seen. Longitudinal data collected annually over three years showed significant

improvements in pitch match completion rates and decreases in pitch match ranges over time.

The findings suggest the importance of device combination and experience with auditory

stimulation for central auditory processing abilities in children during development.