Increased scene complexity during free visual exploration reveals residual unilateral neglect in recovered stroke patients

Using augmented reality to assess spatial neglect: The Free Exploration Test (FET)

BACKGROUND

To capture the distortion of exploratory activity typical of patients with spatial neglect, traditional diagnostic methods and new virtual reality applications use confined workspaces that limit patients' exploration behavior to a predefined area. Our aim was to overcome these limitations and enable the recording of patients' biased activity in real, unconfined space.

METHODS

We developed the Free Exploration Test (FET) based on augmented reality technology. Using a live stream via the back camera on a tablet, patients search for a (non-existent) virtual target in their environment, while their exploration movements are recorded for 30 s. We tested 20 neglect patients and 20 healthy participants and compared the performance of the FET with traditional neglect tests.

RESULTS

In contrast to controls, neglect patients exhibited a significant rightward bias in exploratory movements. The FET had a high discriminative power (area under the curve = 0.89) and correlated positively with traditional tests of spatial neglect (Letter Cancellation, Bells Test, Copying Task, Line Bisection). An optimal cut-off point of the averaged bias of exploratory activity was at 9.0° on the right; it distinguished neglect patients from controls with 85% sensitivity.

DISCUSSION

FET offers time-efficient (execution time: ∼3 min), easy-to-apply, and gamified assessment of free exploratory activity. It supplements traditional neglect tests, providing unrestricted recording of exploration in the real, unconfined space surrounding the patient.

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.

Monocular eye patching modulates ipsilesional reactive saccades and smooth pursuit in patients with left hemispatial neglect

Patients with hemispatial neglect show multiple oculomotor deficits like delayed contralesional saccade latencies, hypometric saccade amplitudes, and impaired smooth pursuit. We aimed to investigate whether modulation of superior colliculus (SC) activity via monocular eye patching improves neglect patients' eye movements to the contralesional side of space. Thirteen neglect patients with left-hemispheric (LH) stroke, 22 neglect patients with right-hemispheric (RH) stroke, and 24 healthy controls completed a video-oculographic examination of horizontal smooth pursuit and reactive saccades twice, while the left or right eye was covered with an eye patch. Independent of the eye patch position, LH and RH patients showed enlarged saccade latencies toward contralesional stimuli. In addition, both during smooth pursuit and reactive saccades, RH patients made significantly fewer rightward saccades when the right than when the left eye was patched. Moreover, during reactive saccades, RH patients made significantly fewer right than left saccades, but only when the right eye was patched. These findings suggest that the ipsilesional eye patch modulated ipsilesional ocular performance in the RH group, presumably resulting from differences in SC activity. Yet, ipsilesional eye patching did not improve eye movements to the contralesional side of space, possibly due to the incomplete contralateral retinocollicular projection in humans.