An immersive virtual reality system for ecological assessment of peripersonal and extrapersonal unilateral spatial neglect

Virtual reality tasks with eye tracking for mild spatial neglect assessment: a pilot study with acute stroke patients

Objective

Increasing evidence shows that traditional neuropsychological tests are insensitive for detecting mild unilateral spatial neglect (USN), lack ecological validity, and are unable to clarify USN in all different spatial domains. Here we present a new, fully immersive virtual reality (VR) task battery with integrated eye tracking for mild visual USN and extinction assessment in the acute state of stroke to overthrow these limitations.

Methods

We included 11 right-sided stroke patients and 10 healthy controls aged 18-75 years. Three VR tasks named the Extinction, the Storage and the Shoot the target tasks were developed to assess USN. Furthermore, neuropsychological assessment examining various parts of cognitive functioning was conducted to measure general abilities. We compared VR and neuropsychological task performance in stroke patients - those with (USN+, n = 5) and without USN (USN-, n = 6) - to healthy controls (n = 10) and tentatively reported the usability of VR system in the acute state of stroke.

Results

Patients had mostly mild neurological and USN symptoms. Nonetheless, we found several differences between the USN+ and healthy control groups in VR task performance. Compared to controls, USN+ patients showed visual extinction and asymmetry in gaze behavior and detection times in distinct spatial locations. Extinction was most evident in the extrapersonal space and delayed detection times on the extreme left and on the left upper parts. Also, USN+ patients needed more time to complete TMT A compared with USN- patients and TMT B compared with controls. VR system usability and acceptance were rated high; no relevant adverse effects occurred.

Conclusion

New VR technology with eye tracking enables ecologically valid and objective assessment methods with various exact measures for mild USN and thus could potentially improve future clinical assessments.

An immersive virtual reality tool for assessing left and right unilateral spatial neglect

The reported rate of the occurrence of unilateral spatial neglect (USN) is highly variable likely due to the lack of validity and low sensitivity of classical tools used to assess it. Virtual reality (VR) assessments try to overcome these limitations by proposing immersive and complex environments. Nevertheless, existing VR-based tasks are mostly focused only on near space and lack analysis of psychometric properties and/or clinical validation. The present study evaluates the clinical validity and sensitivity of a new immersive VR-based task to assess USN in the extra-personal space and examines the neuronal correlates of deficits of far space exploration. The task was administrated to two groups of patients with right (N = 28) or left (N = 11) hemispheric brain lesions, also undergoing classical paper-and-pencil assessment, as well as a group of healthy participants. Our VR-based task detected 44% of neglect cases compared to 31% by paper-and-pencil tests in the total sample. Importantly, 30% of the patients (with right or left brain lesions) with no clear sign of USN on the paper-and-pencil tests performed outside the normal range in the VR-based task. Voxel lesion-symptom mapping revealed that deficits detected in VR were associated with lesions in insular and temporal cortex, part of the neural network involved in spatial processing. These results show that our immersive VR-based task is efficient and sensitive in detecting mild to strong manifestations of USN affecting the extra-personal space, which may be undetected using standard tools.

Neglecting the bottom space: an object-based disorder? A two-case observational study

Altitudinal neglect is an atypical form of spatial neglect where brain-damaged patients neglect the lower, or sometimes the upper, part of the space. Our understanding of this phenomena is limited, with unknown occurrence across different reference frames, such as distance (peripersonal vs. extrapersonal) and system of reference (egocentric vs. allocentric). Two patients with acute bilateral (P1) or right hemispheric (P2) stroke, with signs of bottom altitudinal neglect, underwent an extensive evaluation of neglect within 10 days post-stroke. Assessments involved altitudinal neglect and unilateral spatial neglect (USN) in peripersonal space, exploring egocentric and allocentric signs and in extrapersonal space. Compared to a control group of 15 healthy age-matched subjects, patients showed allocentric and egocentric left USN in peripersonal space, and mostly allocentric signs of altitudinal neglect. No signs of neglect were evidenced in extrapersonal space. Altitudinal neglect could thus present as an allocentric form of spatial neglect, suggesting that allocentric representations may not only affect the deployment of attentional resources along horizontal dimensions but also operate along vertical dimensions. Future studies should deepen our understanding of altitudinal neglect, eventually leading to further unravel spatial processes that control attention, their corresponding brain mechanisms, and implications for patients' rehabilitation and functional outcome.