Perception of dynamic action in patients with schizophrenia.

Neuropsychological studies have revealed that schizophrenic (SZ) patients have severe impairments in the cognitive integration of static and moving perceptual stimuli. Research on knowledge structures has shown that sequences of continuous actions are represented in memory as clusters of goal-directed events in a hierarchical manner. In the present study, we investigated the ability to segment familiar sequences of dynamic goal-directed actions into small and large meaningful units in a group of patients with schizophrenia (N = 16) and a group of healthy control subjects (N = 17). While viewing two videotaped movies, participants were requested to detect the transitions between component events at both low and high levels of the action categorical structure. Both groups detected significantly more events under the small-oriented condition as compared to the large-oriented condition. Differently from normal controls, patients recalled the event scenes in a detailed and fragmentary manner and showed considerable difficulties in detecting large action units. Moreover, low performance on action boundary detection significantly correlated with higher levels of disorganisation symptoms in patients with schizophrenia. A defective conceptual organisation of perceptive action knowledge would help to explain the severe everyday difficulties of these patients both in monitoring their own actions and in understanding others' intentions.