Abnormal speech perception in schizophrenia with auditory hallucinations

The neurobiological mechanism of auditory hallucination (AH) in schizophrenia remains elusive, but AH can be caused by the abnormality in the speech perception system based on the speech perception neural network model.

The purpose of this study was to investigate whether schizophrenic patients with AH have the speech processing impairment as compared with schizophrenic patients without AH, and whether the speech perception ability could be improved after AH had subsided.

Twenty-four schizophrenic patients with AH were compared with 25 schizophrenic patients without AH. Narrative speech perception was assessed using a masked speech tracking (MST) task with three levels of superimposed phonetic noise. Sentence repetition task (SRT) and auditory continuous performance task (CPT) were used to assess grammar-dependent verbal working memory and non-language attention, respectively. These tests were measured before and after treatment in both groups.

Before treatment, schizophrenic patients with AH showed significant impairments in MST compared with those without AH. There were no significant differences in SRT and CPT correct (CPT-C) rates between both groups, but CPT incorrect (CPT-I) rate showed a significant difference. The low-score CPI-I group showed a significant difference in MST performance between the two groups, while the high-score CPI-I group did not. After treatment (after AH subsided), the hallucinating schizophrenic patients still had significant impairment in MST performance compared with non-hallucinating schizophrenic patients.

Our results support the claim that schizophrenic patients with AH are likely to have a disturbance of the speech perception system. Moreover, our data suggest that non-language attention might be a key factor influencing speech perception ability and that speech perception dysfunction might be a trait marker in schizophrenia with AH.