title: Sensitivity of the human binaural cortical steady state response to interaural level differences.
abstract: OBJECTIVE
  Periodic alternations of the interaural correlation of a noise stimulus evoke an auditory steady state response that can be measured at the scalp, providing an objective measure of binaural integration. The purpose of this study was to examine the effect of interaural level differences on this steady state response.
  
  
  METHODS
  Auditory steady state responses at 4 and 8 Hz were recorded to 4 Hz cycles of interaural correlation change of a Gaussian noise in normal-hearing listeners. Responses were recorded with symmetric presentation levels of 80, 60, and 40 dB SPL and with interaural asymmetries ranging from 10 to 40 dB, varying in 10-dB steps.
  
  
  RESULTS
  The 8 Hz response was sensitive to interaural level asymmetry and fell to 50% strength at an asymmetry of 18 dB, although the response was detectable to an asymmetry of 30 dB. A simultaneously present 4 Hz response showed no sensitivity to interaural level difference. Significant responses were recorded in all participants.
  
  
  CONCLUSIONS
  The 8 Hz auditory steady state response to a 4 Hz change in noise interaural correlation might be useful as an objective measure of binaural integration in asymmetric hearing loss. Response amplitude is more negatively affected by small amounts of interaural asymmetry than by large reductions in overall presentation level.
authors.affiliation: Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Massoud
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Aiken
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Newman
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Phillips
authors.forename: Manohar
authors.initials: M
authors.lastname: Bance
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D001300:Audiometry, Evoked Response; D001303:Auditory Cortex / Q000502:physiology; D001309:Auditory Threshold / Q000502:physiology; D004007:Dichotic Listening Tests; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D012016:Reference Values; D055815:Young Adult