Behavioral assessment of auditory processing deficits in schizophrenia: Literature review and suggestions for future research.

During the last decades, a considerable number of studies about auditory processing deficits in schizophrenia have been published, some of them using the term of Auditory Processing Disorder (APD). Due to heterogeneous methodology and inconsistent results concrete conclusions may not be straightforward. We focused on studies that used at least one behavioral test for the assessment of auditory processing in schizophrenia, in order to identify new evidence on auditory processing deficits in schizophrenia, and to consider fields for future research. 28 studies met inclusion criteria and are presented in this review. The articles were divided into three groups, those that implemented a test battery approach, those that used only Dichotic Listening (DL), those that used DL along with imaging or electrophysiology techniques. Most of the studies that implemented a test battery showed significant performance differences between patients and controls. This indicates APD presence. Due to the limited number of studies implementing a test battery, this is not conclusive. The majority of all studies that used a DL task showed that patients' performance or laterality was significantly lower than that of controls. Age, duration of illness, total and specific positive symptoms seem to affect significantly DL performance and auditory laterality. The results support the existence of various schizophrenia subgroups that differ in their auditory processing performance, and also have structural and functional specificities. Further research in the field is needed, especially studies that implement a test battery, and studies that examine possible correlations between clinical variables and auditory processing deficits.