Tracing Links Between Early Auditory Information Processing and Negative Symptoms in Schizophrenia: An ERP Study

Abstract

Background: Negative symptoms represent a heterogeneous dimension with a strong impact on functioning of subjects with schizophrenia (SCZ). Five constructs are included in this dimension: anhedonia, asociality, avolition, blunted affect, and alogia. Factor analyses revealed that these symptoms cluster in two domains: experiential domain (avolition, asociality, and anhedonia) and the expressive deficit (alogia and blunted affect), that might be linked to different neurobiological alterations. Few studies investigated associations between N100, an electrophysiological index of early sensory processing, and negative symptoms, reporting controversial results. However, none of these studies investigated electrophysiological correlates of the two negative symptom domains. Objectives: The aim of our study was to evaluate, within the multicenter study of the Italian Network for Research on Psychoses, the relationships between N100 and negative symptom domains in SCZ. Methods: Auditory N100 was analyzed in 114 chronic stabilized SCZ and 63 healthy controls (HCs). Negative symptoms were assessed with the Brief Negative Symptom Scale (BNSS). Repeated measures ANOVA and correlation analyses were performed to evaluate differences between SCZ and HCs and association of N100 features with negative symptoms. Results: Our findings demonstrated a significant N100 amplitude reduction in SCZ compared with HCs. In SCZ, N100 amplitude for standard stimuli was associated with negative symptoms, in particular with the expressive deficit domain. Within the expressive deficit, blunted affect and alogia had the same pattern of correlation with N100. Conclusion: Our findings revealed an association between expressive deficit and N100, suggesting that these negative symptoms might be related to deficits in early auditory processing in SCZ.

Keywords: EEG; ERP; N100; negative symptoms; schizophrenia.

Figure 1

Grand-average N100 waves elicited by standard (top) and target (bottom) stimuli on the three midlines electrodes for subjects with schizophrenia (SCZ) and healthy controls (HCs). Following stimulus onset, the N100 component was measured in a time window within 80–120 ms. The potential was filtered between 0.01 and 30 Hz to optimize scoring of the N100 component.

Figure 2

Correlations between standard-stimuli N100 amplitude (Fz electrode) with the BNSS total score (A) (r_s = 0.241; p = 0.011) and the expressive deficit domain (B) (r_s = 0.296; p = 0.002) in subjects with schizophrenia. Both correlations remained significant after controlling for the possible confounding effects of positive symptoms, extrapyramidal side effects, depression, and disorganization.