Space Boundaries in Schizophrenia

Abstract

The present study evaluates whether in schizophrenia deficits in specifying social distances appropriately for interindividual interactions might be related to abnormal capabilities in specifying the boundaries of reachable space. Using a stop-distance paradigm, 20 patients with schizophrenia and their controls judged from seven preselected angles when a target reached the boundaries of peripersonal space. Results revealed that spatial perception was similar for patients and controls throughout the workspace with more accurate judgments in the preferred hemi-field. Nevertheless, patients were significantly more variable in their judgments; this variability was correlated with the PANSS disorganization cluster. In task 2, participants were required to judge either the boundaries of reachable space (target was an object) or to evaluate social distances (target was a person). Results revealed here again increased judgment variability in schizophrenia, in both situations. Of key importance was that results were normalized in the patients, when judgments were made through voluntary movement. These results argue for a similar brain mechanism for the determination of space and social distances. Furthermore, they suggest an important role of voluntary movement for the creation of stronger motor representations of action goals, which provide the basis for more accurate judgments of space boundaries during both physical and social interactions. The findings are discussed in light of the embodied theory of cognition and their implications for social skills in patients suffering from mental illnesses.