Measuring sound detection and reaction time in infant and toddler cochlear implant recipients using an observer-based procedure: a first report.

Objectives: First, to establish the feasibility of the observer-based psychophysical procedure (OPP) in measuring sound detection in infant and toddler cochlear implant (CI) recipients. Second, to measure the psychometric function for detection (PFD) from individual subjects. Third, to determine whether reaction time (RT) provides information about the auditory sensitivity of young CI users.

Design: Twelve CI recipients, 11 to 32 mo old, participated in our study. Initially, tones were presented in sound field, and children learned to respond when they heard tones but not at other times. Once an 80% correct criterion was met in sound field, a novel stimulation paradigm was used to present stimuli to a single electrode while the child listened to acoustic input on most other electrodes using their usual map. The PFD and RT were measured using this single-electrode stimulation paradigm.

Results: Eleven subjects met criterion, 6 within the minimum possible number of trials. For eight subjects, the asymptotic level of detecting single-electrode stimuli averaged 86% correct, similar to levels achieved by normal-hearing infants and toddlers detecting pure tones. The PFD slope of infant and toddler CI recipients was less than or equal to the slope for adult CI users reported in previous studies. RT decreased significantly with stimulus level in four children.

Conclusions: These preliminary results suggest that psychophysical detection data can be obtained from infant and toddler CI recipients using OPP. The PFD of young CI users may be shallower than that of adult CI users. Relatively good asymptotic detection performance implies that young CI users are more attentive to sound than has been suggested in previous studies. RT tended to be a less reliable measure of detection, but methodological changes could improve its utility.