Computer Science Colloquium, 2008-2009

Abstract:

Our lab has spent several years developing a large-workspace, three-dimensional (3D) haptics/graphics system which is being used for a variety of studies focused mainly on the assessment and rehabilitation of stroke and traumatic brain injury survivors. In this talk I will focus on the recently-developed Virtual Environment for Spatial Neglect Assessment (VESNA) application.

Spatial neglect (a failure to be aware of and respond to objects that appear on the contralesional side of space) has proven to be a significant factor limiting the success of the rehabilitation process following stroke. Current tests for neglect however have several substantial drawbacks, which often lead to a misdiagnosis of less severe cases. Further, while neglect has been reported in the past along independent spatial dimensions, current tests are mostly limited to the horizontal dimension. To date, 35 right-hemisphere stroke patients, with and without neglect, and 17 healthy controls were tested. Subjects were instructed to detect (perception task) and reach (motor task) toward targets that appeared in various locations within a 3D virtual scene. Perceptual performance and overall movement quality were investigated. Our results have demonstrated the feasibility and sensitivity of the virtual reality system for diagnosing mild neglect and monitoring patients’ recovery within a 3D space. For the perceptual task, in contrast with control subjects (healthy and stroke without neglect), all neglect patients exhibited asymmetries of performance in one or more spatial dimensions. Importantly, performance of these patients on the standard paper-and-pencil tests was less conclusive. Testing a second approach for characterizing neglect within the 3D space revealed strong dependence on the angular coordinate (with respect to the horizontal gaze angle) in two neglect patients. To our knowledge, this is the first behavioral evidence for such dependence in neglect. For the motor task we found that compared to healthy controls, stroke patients had longer movement times, increased number of corrective sub-movements and lower peak velocity. However, except for movement initiation time, the observed variations across space of other motor task’s kinematic measures did not differ between patients with and without neglect. This result supports the hypothesis that neglect does not directly cause specific motor impairments, but rather any motor impairments observed are perceptual in origin. Results from this study should present clinicians with a more precise description of a patient’s deficit which would further help direct training.