Simulating hemispatial neglect with virtual reality

Abstract

Background: Hemispatial neglect is a cognitive disorder defined as a lack of attention for stimuli contra-lateral to the brain lesion. The assessment is traditionally done with basic pencil and paper tests and the rehabilitation programs are generally not well adapted. We propose a virtual reality system featuring an eye-tracking device for a better characterization of the neglect that will lead to new rehabilitation techniques.

Methods: This paper presents a comparison of eye-gaze patterns of healthy subjects, patients and healthy simulated patients on a virtual line bisection test. The task was also executed with a reduced visual field condition hoping that fewer stimuli would limit the neglect.

Results: We found that patients and healthy simulated patients had similar eye-gaze patterns. However, while the reduced visual field condition had no effect on the healthy simulated patients, it actually had a negative impact on the patients. We discuss the reasons for these differences and how they relate to the limitations of the neglect simulation.

Conclusion: We argue that with some improvements the technique could be used to determine the potential of new rehabilitation techniques and also help the rehabilitation staff or the patient's relatives to better understand the neglect condition.

Figure 1

System. From left to right: virtual world monitoring, immersive workspace with eye-tracking device and a Phantom Omni haptics device, eye-tracking computer.

Figure 2

Virtual line bisection. Top: In the normal condition, the haptic device controls the pencil. When the pencil is lift up, the stroke is replaced by a cross if the stroke intersects the line. The subject can retry or validate his bisection and move on to the next trial. Bottom left: a montage showing the center of the lines (red crosses) in the three conditions (left sided, centered and right sided) and the extents of the lines when centered (in black). Bottom right: a montage showing the virtual line bisection in the reduced visual condition. The virtual world is viewed through a moving hole (only the bright area is visible). The subject has to stop the moving hole when the green cross reaches the middle of the line. When a choice is made, the whole virtual world is displayed. The subject can retry or validate and move on to the next trial.

Figure 3

Eye-gaze patterns. Top: eye-gaze of a healthy subject during a task in the reduced visual field condition. Bottom: eye-gaze of Patient K. during a task in the reduced visual field condition.

Figure 4

Overall results of each groups for each condition. The error represents the deviation from the true middle of the line. It is expressed in terms of the percentage of half the length of the line. An error of 100% means that the bisection was done on the extreme extent of the line.

Figure 5

Per trial results for the simulated patients group. Performance of the simulated patients group in terms of the error in percent of half the length of the line for each trial ordered by location and length.

Figure 6

Per trial results for Patient K. Patient K.'s per trial performance for both conditions.