Effects of Task Constraints on Unimanual and Bimanual Movements in Patients With Schizophrenia

Abstract

Although occupational therapists commonly treat patients with schizophrenia in clinical practice the profession has been lacking sufficient evidence supporting its effectiveness Recent studies suggested that schizophrenia affects not only mental function but also movements in patients The knowledge of movement rehabilitation for patients with schizophrenia has not been developed properly now Object size object distance and target speed of movement tasks are common task constraints in rehabilitation settings and can affect movement formation effectively in healthy people Therefore the purposes of this study were to compare the movements of patients with mild schizophrenia and healthy controls and to examine effects of changes in object size object distance and target speed on movements in patients The first experiment of this study was to examine effects of object size and distance on unimanual movements on the reach-to-grasp task in patients with mild schizophrenia Twenty-nine patients and 15 age- and gender-matched healthy controls were required to reach for and grasp an object of varying sizes (small v s large) and distances (near v s far) by the dominant hand as quickly as possible We measured movement time peak velocity the path length ratio the percentage of time to peak velocity and the number of movement units to represent movement speed forcefulness spatial efficiency the control strategy and smoothness Patients showed similarly forceful feedback-dependent and smooth but slower and less direct movements than controls Increasing object size or shortening object distance induced faster and more preprogrammed movements in patients Increasing object distance induced more direct movements in patients Increasing object size or object distance induced more forceful movements in patients The second experiment was to examine effects of object size on unimanual and bimanual movements on the bimanual assembly task in patients with mild schizophrenia Fifteen patients and 15 age- and gender-matched healthy controls were instructed to bimanually reach for and assemble objects to the stationary target as quickly as possible We manipulated the object size for the left hand (small vs large) and measured movement time peak velocity and bimanual synchronization to represent movement speed forcefulness and bimanual coordination Patients showed slower and less forceful unimanual movements and less coordinated bimanual movements than controls Increasing object size elicited faster and more forceful unimanual movements and more coordinated bimanual movements in patients The third experiment was to examine effects of target speed on unimanual and bimanual movements on the bimanual assembly task in patients with mild schizophrenia Fifteen patients and 15 age- and gender-matched healthy controls were instructed to bimanually reach for (prehension) and assemble objects (assembly) to the moving target of varying speed (fast v s slow) as quickly as possible We measured movement time the number of movement units and bimanual synchronization to represent movement speed smoothness and bimanual coordination Increasing target speed induced faster smoother and more coordinated movements in patients Under the slow-target condition patients had slower and less coordinated prehension as well as slower more uneven and less coordinated assembly than controls Under the fast-target condition patients still had slower and less coordinated prehension than controls but their assembly improved to a level similar to that of controls This study provides insights into the unimanual and bimanual movement features in patients with mild schizophrenia and suggests the need for movement therapy for patients with schizophrenia Additionally this study specifies clinical practice guidelines of manipulating task constraints for optimizing patients’ movements and contributes to the practice of evidence-based occupational therapy for patients with mild schizophrenia

Date of Award	2015 May 18
Original language	English
Supervisor	Hui-Ing Ma (Supervisor)