title: Contralateral inhibition of distortion product otoacoustic emissions in children with auditory processing disorders.
abstract: OBJECTIVE
  The purpose of this study was to evaluate changes in distortion product otoacoustic emission (DPOAE) level elicited by contralateral noise in children with normal hearing, and those with auditory processing disorders (APD) whose audiometric thresholds were normal. It was hypothesized that children with APD would demonstrate smaller changes.
  
  
  METHODS
  Levels of DPOAEs were recorded for f(2) stimulus tones fixed at 2, 3, and 4 kHz while the f(1) tone was ramped around nominal stimulus frequency ratios of f(2)/f(1) = 1.22 and 1.10. Mean and maximum absolute changes resulting from contralateral broadband noise presented at 60 dB SPL were evaluated across the DPOAE frequency bands for each individual and for both groups of subjects.
  
  
  METHODS
  Eight normal-hearing children and eight children with APD whose audiometric thresholds were normal participated.
  
  
  RESULTS
  There were no significant differences in DPOAE inhibition between normal hearing and APD groups, or previously recorded adult data. Mean absolute changes were typically near 1 dB, except for f(2) = 4 kHz and the stimulus frequency ratio 1.22 where inhibition was only 0.5 dB. However, there were individual children in both groups who demonstrated larger DPOAE changes for some stimulus parameters.
  
  
  CONCLUSIONS
  The inhibition of otoacoustic emissions requires further study in APD children.
authors.affiliation: National Centre for Audiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Blake E
authors.initials: BE
authors.lastname: Butler
authors.forename: David W
authors.initials: DW
authors.lastname: Purcell
authors.forename: Prudence
authors.initials: P
authors.lastname: Allen
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D001299:Audiometry; D001306:Auditory Pathways / Q000503:physiopathology*; D001308:Auditory Perceptual Disorders / Q000503:physiopathology*; D001309:Auditory Threshold; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous