The neural substrates of diminished humor comprehension in schizophrenia and its relationship with psychopathology

Patients with schizophrenia commonly revealed difficulties in understanding humor. Previous research suggested links between impaired humor comprehension, psychopathology symptoms and cognitive deficits. In this study, we investigated the associations between neural substrates of humor processing and psychopathology and cognition in schizophrenia. We assessed 25 schizophrenia outpatients in an functional magnetic resonance imaging (fMRI) procedure and 40 in an electroencephalography (EEG) procedure. A punchline-based humor comprehension task was used in which outpatients rated stories by their comprehensibility and funniness. The symptom severity and cognition were correlated with activation within the humor processing network using fMRI and effective connectivity using an EEG-based directed transfer function (DTF) method. More severe positive and disorganization symptoms were associated with impaired humor comprehension and with altered temporo-parietal effective connectivity during humor processing. More severe excitement and emotional reactivity symptoms were associated with increased activation in the bilateral frontal and temporo-parietal regions. Moreover, schizophrenia outpatients with better cognitive functioning were more accurate in humor comprehension that was associated with increased fronto-temporo-parietal activation and effective connectivity. We found the intensity of humor processing (fMRI) in schizophrenia is related to the level of cognitive abilities and the severity of schizophrenia psychopathology that is also reflected in altered effective connectivity (EEG-DTF) in the humor processing network.