Aims: Abnormal emotion processing in schizophrenia affects social and functional outcome. Spatiotemporal brain mechanisms underlying this deficit are unclear.
Materials and methods: Event-related potential (ERP) responses to emotional and neutral face processing during an implicit (gender detection) and an explicit (expression detection) task were compared between a group of healthy volunteers (n=10) and a group of patients with schizophrenia (n=10).
Results: Whereas patients had normal primary visual cortex responses, the early modulation of occipital, temporal, and frontal responses by emotional expression observed in controls was absent in patients. The occipito-temporal N170 amplitude was reduced in patients relative to controls during expression detection, but not during gender detection. Frontal activity within 180-250ms was reduced in patients compared to controls. As opposed to controls, no significant difference was seen in patients at the right temporal electrode (T6) between amplitudes of long-latency ERPs elicited by distinct emotions during the expression detection task.
Conclusion: In patients with schizophrenia, abnormal early extraction of expression-related information in the occipito-temporal cortex (before 170ms) impairs structural encoding of facial expressions (N170) and may disrupt motivation- and task-dependent context processing (180-250ms time window) of expression-related facial features. Moreover, top-down neuromodulation from frontal and limbic structures to visual occipito-temporal cortex may not be sufficient to optimize the extraction of expression-specific face features.