title: The Hyperactivity of Efferent Auditory System in Patients with Schizophrenia: A Transient Evoked Otoacoustic Emissions Study.
abstract: OBJECTIVE
  Electrophysiological studies, which are mostly focused on afferent pathway, have proven that auditory processing deficits exist in patients with schizophrenia. Nevertheless, reports on the suppressive effect of efferent auditory pathway on cochlear outer hair cells among schizophrenia patients are limited. The present, case-control, study examined the contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) in patients with schizophrenia.
  
  
  METHODS
  Participants were twenty-three healthy controls and sixteen schizophrenia patients with normal hearing, middle ear and cochlear outer hair cells function. Absolute non-linear and linear TEOAEs were measured in both ears by delivering clicks stimuli at 80 dB SPL and 60 dB SPL respectively. Subsequently, contralateral suppression was determined by subtracting the absolute TEOAEs response obtained at 60 dBpe SPL during the absence and presence of contralateral white noise delivered at 65 dB HL. No attention tasks were conducted during measurements.
  
  
  RESULTS
  We found no significant difference in absolute TEOAEs responses at 80 dB SPL, in either diagnosis or ear groups (p>0.05). However, the overall contralateral suppression was significantly larger in schizophrenia patients (p<0.05). Specifically, patients with schizophrenia demonstrated significantly increased right ear contralateral suppression compared to healthy control (p<0.05).
  
  
  CONCLUSIONS
  The present findings suggest increased inhibitory effect of efferent auditory pathway especially on the right cochlear outer hair cells. Further studies to investigate increased suppressive effects are crucial to expand the current understanding of auditory hallucination mechanisms in schizophrenia patients.
authors.affiliation: Audiology Programme, School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.; Audiology Programme, School of Rehabilitation Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Wilayah Persekutuan, Malaysia.
authors.forename: Noor Alaudin
authors.initials: NA
authors.lastname: Abdul Wahab
authors.affiliation: Department of Psychiatry, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Center, Wilayah Persekutuan, Malaysia.
authors.forename: Suzaily
authors.initials: S
authors.lastname: Wahab
authors.affiliation: Department of Psychiatry, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Center, Wilayah Persekutuan, Malaysia.
authors.forename: Abdul Hamid
authors.initials: AH
authors.lastname: Abdul Rahman
authors.affiliation: Department of Otorhinolaryngology, School of Medicine, Universiti Sains Malaysia, Kelantan, Malaysia.
authors.forename: Dinsuhaimi
authors.initials: D
authors.lastname: Sidek
authors.affiliation: Audiology Programme, School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.
authors.forename: Mohd Normani
authors.initials: MN
authors.lastname: Zakaria
keywords: Efferent pathways; Hair cells; Otoacoustic emissions; Schizophrenia