Searching for meaning in meaningless gestures, pathologic activity in amygdala, hippocampus and temporal pole during planning of gestures in schizophrenia

Introduction Schizophrenia is characterized by poor social interaction contributing to poor functional outcome. Particularly nonverbal communication is disturbed. Neural correlates of impaired gesturing are currently unclear. We thus tested functional correlates of gesturing in schizophrenia patients and healthy controls. Methods We tested 22 patients and 25 controls with an event-related fMRI (instructed delay) paradigm to dissociate brain activation during planning and execution of meaningful (e.g. use scissors) and meaningless novel gestures. Preprocessing included realignment, coregistration, normalization and spatial smoothing. We used a two stage mixed effects model for statistical analysis. Conditions were contrasted against a linguistic control within and between groups. We correlated psychopathological characteristics with beta estimates of brain areas with between group effects. Results During planning and execution of both gesture subtypes both groups activated brain areas of the ventral and dorsal stream. However patients’ activity was less prominent and more left lateralized. During planning patients showed additional activity in bilateral temporal poles, amygdala and hippocampus associated with the level of delusions. Furthermore patients had increased dorsomedial prefrontal cortex and precuneus activity when planning meaningless gestures. Conclusion During the planning of meaningless gestures we detected aberrant activation of limbic structures in patients typically implicated in delusion formation, which also correlated with current severity of delusions. Moreover, planning of meaningless gestures relied on areas relevant for strategic control and attention. These results argue for a pathologic search for meaning in neutral gestures and increased control effort during planning of meaningless gestures in schizophrenia.