Auditory efferent suppression during alternate auditory attention in schizophrenia patients with auditory hallucinations

Auditory hallucination is a complex and not yet fully understood phenomenon, and further research is necessary to elucidate the underlying mechanisms. Previous research has shown the possible contribution of abnormal efferent auditory pathways to auditory hallucinations. Given the structural and functional top-down connection between the auditory cortex and the cochlea, this study investigated the efferent auditory system in schizophrenia patients experiencing verbal auditory hallucinations (VAHs). Alternate Auditory Attention (ALAUDIN©) tasks were integrated with Contralateral Suppression of Otoacoustic Emissions (CSOAE) tasks as an assessment method. A total of 57 healthy controls (HCs) and 10 schizophrenia patients-five with recent hallucinations (SRH group) and five with nonrecent hallucinations (SNRH group) participated. Contralateral suppressors, which included white noise (WN) alone and WN in combination with ALAUDIN© tasks, were integrated with an otoacoustic emission (OAE) system to measure the suppression of cochlear outer hair cells. While no significant differences in suppression were found between the left and right ears across all groups, the SRH group demonstrated significantly greater suppression than did the HC group for contralateral suppressor 4 (CS4). Notably, incorporating the ALAUDIN© tasks could be used to measure abnormalities in the efferent auditory pathway in patients with schizophrenia with VAHs. These results suggest that the ALAUDIN©-CSOAE test could be used to examine efferent auditory pathways and differentiate schizophrenia patients with recent VAHs from healthy individuals, but further research with larger sample sizes is warranted to validate these findings.