Abstract
Individuals with schizophrenia, particularly those with passivity symptoms, may not feel in control of their actions, believing them to be controlled by external agents. Cognitive operations that contribute to these symptoms may include abnormal processing in agency as well as body representations that deal with body schema and body image. However, these operations in schizophrenia are not fully understood, and the questions of general versus specific deficits in individuals with different symptom profiles remain unanswered. Using the projected-hand illusion (a digital video version of the rubber-hand illusion) with synchronous and asynchronous stroking (500 ms delay), and a hand laterality judgment task, we assessed sense of agency, body image, and body schema in 53 people with clinically stable schizophrenia (with a current, past, and no history of passivity symptoms) and 48 healthy controls. The results revealed a stable trait in schizophrenia with no difference between clinical subgroups (sense of agency) and some quantitative (specific) differences depending on the passivity symptom profile (body image and body schema). Specifically, a reduced sense of self-agency was a common feature of all clinical subgroups. However, subgroup comparisons showed that individuals with passivity symptoms (both current and past) had significantly greater deficits on tasks assessing body image and body schema, relative to the other groups. In addition, patients with current passivity symptoms failed to demonstrate the normal reduction in body illusion typically seen with a 500 ms delay in visual feedback (asynchronous condition), suggesting internal timing problems. Altogether, the results underscore self-abnormalities in schizophrenia, provide evidence for both trait abnormalities and state changes specific to passivity symptoms, and point to a role for internal timing deficits as a mechanistic explanation for external cues becoming a possible source of self-body input.
Highlights
In the field of cognitive neuroscience, the “sense of self ” refers to a complex framework, which is derived from cognitive, sensory, and motor systems
The results revealed a stable trait in schizophrenia with no difference between clinical subgroups and some quantitative differences depending on the passivity symptom profile
Such self-abnormalities appear to be characteristic of schizophrenia [3, 4], and are pronounced in passivity symptoms, where individuals do not feel in control of their movements and believe that their actions and intentions are controlled by an external agent
Summary
In the field of cognitive neuroscience, the “sense of self ” refers to a complex framework, which is derived from cognitive, sensory, and motor systems. Kurt Schneider noted that symptoms described “a loss of the very contours of the self ” [1], and Bleuler [2] described the tearing apart or splitting of psychic functions. Such self-abnormalities appear to be characteristic of schizophrenia [3, 4], and are pronounced in passivity symptoms (experience of alien control), where individuals do not feel in control of their movements and believe that their actions and intentions are controlled by an external agent.
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