Trajectory estimation in schizophrenia.

Two experiments were conducted to investigate the ability of schizophrenia patients to maintain internal representation over time and space. It has been hypothesized that the ability to guide behavior by internal representation, mediated by the dorsolateral prefrontal cortex (DLPFC), is impaired in schizophrenia [e.g. Goldman-Rakic, P.S., 1996. The functional parcellation of dorsolateral prefrontal cortex and the heterogeneous facets of schizophrenia. In: Matthysse, S., Levy, D.L. (Eds.), Psychopathology: Evolution of a New Science. Cambridge University Press, Cambridge]. In Experiment 1, subjects observed a target, which traveled behind an opaque wall during a part of its trajectory. The task was to accurately assess the speed of the target by predicting when the target would re-emerge on the other side of the wall. In Experiment 2, subjects were asked to estimate the spatial trajectory of an established target path when it was partially occluded from view by another object. Schizophrenia patients were impaired in estimating the speed of a moving target and in estimating the spatial trajectory, without showing deficits in the control tasks. These results suggest that schizophrenia patients may not be able to accurately maintain the internal representation of a target over time and space. Such deficits may have deleterious consequences in goal-directed behavior.