Movement planning and online control in multiple sclerosis: assessment using a Fitts law reciprocal aiming task.

OBJECTIVE: We sought to quantify subtle changes in motor control in multiple sclerosis (MS) using a Fitts law reciprocal aiming task presented on a computer touchscreen. BACKGROUND: Upper-limb motor control is impaired in MS. However, many commonly used motor assessments do not detect subtle changes in motor function or differentiate between aspects of movement such as planning and online control. Fitts law states that movement time varies as a function of task difficulty, with smaller targets and greater distances making the task more difficult. METHODS: We gave a Fitts aiming task to 22 patients with MS and 22 matched controls. We manipulated movement difficulty by changing the targets' size and distance apart. RESULTS: The patients spent a significantly longer time than the controls stationary in each target before starting the next movement, and had a lower peak velocity, suggesting deficits in movement planning. The patients also spent longer in the deceleration phase of each movement, indicating deficits in the online control of movement. CONCLUSIONS: The computerized Fitts task allows quick, easy, and sensitive measurement of subtle aspects of movement. This task should be useful in clinical and research settings for assessing MS motor symptoms, disease progression, and treatment efficacy.

Cognition and eye movements: assessment of cerebral dysfunction.

BACKGROUND: Many neurological disorders show deficits in ocular motor function. In the past, evaluation has been limited to assessing abnormalities largely generated by pathology of the brainstem andcerebellum. In disorders that primarily or substantially, affect the cerebral hemispheres, disruption of cognitive processes occur, often early in the clinical course. While neuropsychological testing traditionally is used to measure cognitive performance, the cerebral influences on the ocular motor system provides another quantitative paradigm. This review explores the relationship between cognitive sensory processing and execution of planned ocular motor tests in Parkinson's disease, Huntington's disease and multiple sclerosis and explores areas of clinical utility. METHODS: Review of the literature regarding cognitive and ocular motor abnormalities in neurological disease. RESULTS: The literature indicates that in systems degeneration there are abnormalities of cognitive processing, defined both by conventional behavioural testing and by assessment of cognitive function utilizing ocular motor studies, which characterise those processes. Moreover, in diffuse disease, in processes such as multiple sclerosis, the assessment of cognitive processes involved in ocular motor function may well provide an added level of sensitivity indicating more widespread pathology than would be apparent with conventional clinical assessment. CONCLUSIONS: Assessment of cognitive function in the ocular motor system may provide insight into cerebral function, in health and disease, and may provide both diagnostic information and permit quantification of deficit in future.