Neural basis of altered physical and social causality judgements in schizophrenia

Patients with schizophrenia (SZ) often make aberrant cause and effect inferences in non-social and social situations. Likewise, patients may perceive cause-and-effect relationships abnormally as a result of an alteration in the physiology of perception. The neural basis for dysfunctions in causality judgements in the context of both physical motion and social motion is unknown. The current study used functional magnetic resonance imaging (fMRI) to investigate a group of patients with SZ and a group of control subjects performing judgements of causality on animated collision sequences (launch-events, Michotte, 1963) and comparable "social" motion stimuli. In both types of animations, similar motion trajectories of the affected object were configured, using parametrical variations of space (angle deviation) and time (delay). At the behavioural level, SZ patients made more physical and less social causal judgements than control subjects, and their judgements were less influenced by motion attributes (angle/time delay). In the patients group, fMRI revealed greater BOLD-responses, during both physical and social causality judgements (group×task interaction), in the left inferior frontal gyrus (L.IFG). Across conditions (main effect), L.IFG-interconnectivity with bilateral occipital cortex was reduced in the patient group. This study provides the first insight into the neural correlates of altered causal judgements in SZ. Patients with SZ tended to over-estimate physical and under-estimate social causality. In both physical and social contexts, patients are influenced less by motion parameters (space and time) than control subjects. Imaging findings of L.IFG-disconnectivity and task-related hyper-activation in the patient group could indicate common dysfunctions in the neural activations needed to integrate external cue-information (space/time) with explicit (top-down) cause-effect judgements of object motions in physical and social settings.