Preliminary Study on the Assessment of Patients with Impaired Visuospatial Ability in Three-Dimensional Space Using a New Head Mounted Display System with Virtual Reality Technology

Toshiaki Tanaka , Norio Kato, Mizuki Yagi , Nobuya Hashimoto, Akira Kudo, Syunichi Sugihara

unilateral spatial neglect, virtual reality technology, head mounted display system.

Various disturbances of visual space recognition include unilateral spatial neglect (USN) has been strongly associated with an increased risk for injury and with poor functional outcome. The purpose of this study was to understand more accurately the pathology of USN using a new HMD system with virtual reality technology. In addition, brain activity measurements and analysis by using HMD in this study were done using near infrared spectroscopy (NIRS). Two experiments were performed as follows; (a) Experimental A (Object cancellation evaluation by using HMD): Unlike the line cancellation test in the BIT that one test used in the clinical evaluation of USN, in this case we tried to assess USN by conducting a test in which the task was to cancel three-dimensional objects using HMD. In this study, the respective USN symptoms in the egocentric and object-centered coordinate systems were evaluated. The objects were placed at depths of 35 cm, 45 cm, and 55 cm. The subject was a stroke patient (patientⅠ) with USN who was 83 years old. (b) Experimental B (Brain activity measurement and analysis during task execution): The subject was a stroke patient (patientⅡ) with USN who was 67 years old. The same task as in Experiment I is performed, and the brain activity during the task movement is measured using NIRS. The subject took a resting chair, rested for 5 minutes, and then started the task. The NIRS measurement sites were from the inferior frontal gyrus to the middle frontal gyrus of both left and right sides.  According to the results of in the experiment A, the cancellation rate showed the same trend that the left area was lower than central area and right area. The cancellation rate was the lowest at the greatest of the three depth distances, 55 cm. This can only be seen with three-dimensional VR space as in this experiment, as scoring cannot be done on the BIT line cancellation test since tests related to depth cannot be performed. In the experiment B, greater values of oxygenated hemoglobin (oxy-Hb) related to brain activity was seen during the task than at rest in the patient with USN. Furthermore, the patient’s brain activity on the paralyzed side was lower than the healthy side.  In conclusions, the results suggest the possibility of analyzing versatile pathological conditions of USN with newly HMD system. Moreover, the results of NIRS suggested that it may also be to clarify brain activity in relation to the pathological condition of USN.

https://doi.org/10.31871/IJNTR.7.8.13