Intentional gaze shift to neglected space: a compensatory strategy during recovery after unilateral spatial neglect

Abstract

Unilateral spatial neglect is a common neurological syndrome following predominantly right hemispheric stroke. While most patients lack insight into their neglect behaviour and do not initiate compensatory behaviours in the early recovery phase, some patients recognize it and start to pay attention towards the neglected space. We aimed to characterize visual attention capacity in patients with unilateral spatial neglect with specific focus on cortical processes underlying compensatory gaze shift towards the neglected space during the recovery process. Based on the Behavioural Inattention Test score and presence or absence of experience of neglect in their daily life from stroke onset to the enrolment date, participants were divided into USN+‰‰+ (do not compensate, n = 15), USN+ (compensate, n = 10), and right hemisphere damage groups (no neglect, n = 24). The patients participated in eye pursuit-based choice reaction tasks and were asked to pursue one of five horizontally located circular objects flashed on a computer display. The task consisted of 25 trials with 4-s intervals, and the order of highlighted objects was randomly determined. From the recorded eye tracking data, eye movement onset and gaze shift were calculated. To elucidate the cortical mechanism underlying behavioural results, electroencephalagram activities were recorded in three USN+‰‰+, 13 USN+ and eight patients with right hemisphere damage. We found that while lower Behavioural Inattention Test scoring patients (USN+‰‰+) showed gaze shift to non-neglected space, some higher scoring patients (USN+) showed clear leftward gaze shift at visual stimuli onset. Moreover, we found a significant correlation between Behavioural Inattention Test score and gaze shift extent in the unilateral spatial neglect group (r = -0.62, P < 0.01). Electroencephalography data clearly demonstrated that the extent of increase in theta power in the frontal cortex strongly correlated with the leftward gaze shift extent in the USN+‰‰+ and USN+ groups. Our results revealed a compensatory strategy (continuous attention to the neglected space) and its neural correlates in patients with unilateral spatial neglect. In conclusion, patients with unilateral spatial neglect who recognized their own neglect behaviour intentionally focused on the neglected space as a compensatory strategy to avoid careless oversight.

Anatomical predictors of successful prism adaptation in chronic visual neglect

“…This result suggests that PA improves left neglect by allowing left-hemisphere attentional networks to access information processed by the lesioned right hemisphere, through the callosal body and genu. An implication of prefrontal circuits in neglect compensation has been hypothesized on the basis of behavioural evidence (Bartolomeo, 1997;Bartolomeo, 2000), and recently confirmed by electrophysiological measures (Takamura et al, 2016). Also consistent with our results, cathodal transcranial direct current stimulation applied over the left posterior parietal cortex interfered with the beneficial effect of PA on neglect (Làdavas et al, 2015).…”

Anatomical predictors of successful prism adaptation in chronic visual neglect

“…This result suggests that PA improves left neglect by allowing left-hemisphere attentional networks to access information processed by the lesioned right hemisphere, through the callosal body and genu. An implication of prefrontal circuits in neglect compensation has been hypothesized on the basis of behavioral evidence 40 , and recently confirmed by electrophysiological measures 41 . Also consistent with our results, cathodal transcranial direct current stimulation applied over the left posterior parietal cortex interfered with the beneficial effect of PA on neglect 42 .…”

E-TAN, a technology-enhanced platform with tangible objects for the assessment of visual neglect: A multiple single-case study

“…E-BTT analysis also offers the possibility of determining the localization of the first disk, which can give a clue to identify the initial attentional focus during the exploration of the surface. During neglect compensation, some patients might still initiate their exploration from the right side, and then reach the left part of the board (Bartolomeo, 1997(Bartolomeo, , 2000; other patients, perhaps those who better recognize their neglect, might intentionally start their exploration from the left (Takamura, Imanishi, Osaka, Ohmatsu, Tominaga, Yamanaka, Morioka & Kawashima, 2016). E-BTT can record such shifts of exploratory preferences during patient follow-up, and thus characterize distinct behavioral patterns even in patients whose final performance reaches the normal limits.…”