Psychiatry Investig.  2016 Jan;13(1):82-88. 10.4306/pi.2016.13.1.82.

The Hyperactivity of Efferent Auditory System in Patients with Schizophrenia: A Transient Evoked Otoacoustic Emissions Study

• Abdul Wahab NA
• Wahab S
• Abdul Rahman AH
• Sidek D
• Zakaria MN

• KMID: 2316600
• DOI: http://doi.org/10.4306/pi.2016.13.1.82

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).
CONCLUSION
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.

Keyword

Schizophrenia; Efferent pathways; Otoacoustic emissions; Hair cells

MeSH Terms

Afferent Pathways
Auditory Pathways
Case-Control Studies
Diagnosis
Ear
Ear, Middle
Efferent Pathways
Hair
Hallucinations
Hearing
Humans
Noise
Schizophrenia*