Abstract
The eye-tracking study aimed at assessing spatial biases in visual exploration in patients after acute right MCA (middle cerebral artery) stroke. Patients affected by unilateral neglect show less functional recovery and experience severe difficulties in everyday life. Thus, accurate diagnosis is essential, and specific treatment is required. Early assessment is of high importance as rehabilitative interventions are more effective when applied soon after stroke. Previous research has shown that deficits may be overlooked when classical paper-and-pencil tasks are used for diagnosis. Conversely, eye-tracking allows direct monitoring of visual exploration patterns. We hypothesized that the analysis of eye-tracking provides more sensitive measures for spatial exploration deficits after right middle cerebral artery stroke. Twenty-two patients with right MCA stroke (median 5 days after stroke) and 28 healthy controls were included. Lesions were confirmed by MRI/CCT. Groups performed comparably in the Mini–Mental State Examination (patients and controls median 29) and in a screening of executive functions. Eleven patients scored at ceiling in neglect screening tasks, 11 showed minimal to severe signs of unilateral visual neglect. An overlap plot based on MRI and CCT imaging showed lesions in the temporo–parieto–frontal cortex, basal ganglia, and adjacent white matter tracts. Visual exploration was evaluated in two eye-tracking tasks, one assessing free visual exploration of photographs, the other visual search using symbols and letters. An index of fixation asymmetries proved to be a sensitive measure of spatial exploration deficits. Both patient groups showed a marked exploration bias to the right when looking at complex photographs. A single case analysis confirmed that also most of those patients who showed no neglect in screening tasks performed outside the range of controls in free exploration. The analysis of patients’ scoring at ceiling in neglect screening tasks is of special interest, as possible deficits may be overlooked and thus remain untreated. Our findings are in line with other studies suggesting considerable limitations of laboratory screening procedures to fully appreciate the occurrence of neglect symptoms. Future investigations are needed to explore the predictive value of the eye-tracking index and its validity in everyday situations.
Highlights
Neglect has been defined as the inability to report, respond, or orient to novel or meaningful stimuli presented to the side opposite a brain lesion [1, 2]
Patients were classified as showing no neglect (NN-patients; n = 11; median = 0) when they had a score of 0 in the screening tasks, and as showing minimal to severe signs of neglect when they scored 1 or higher in the screening tasks (NE-patients; n = 11; median 2, range 1 to 5)
The present study investigated visual exploration in right MCA stroke patients in paper-and-pencil screening tasks and in two eye-tracking tasks
Summary
Neglect has been defined as the inability to report, respond, or orient to novel or meaningful stimuli presented to the side opposite a brain lesion [1, 2]. Patients and controls performed the Mini–Mental State Examination (MMSE; controls only above the age of 60), the Frontal Assessment Battery [FAB; [37, 38]] and a clock drawing task [CLOX; [39]]. A test battery including four paper-and-pencil cancelation tasks [Symbol Cancelation, Line Crossing, Ota Circle Task and Defect Detection Task [22, 40,41,42]], the clock drawing task, the copying task of the MMSE, and a number reading task (three pages with three horizontally presented two-digit numbers presented on the computer screen) was used for neglect screening. 18) Ota circle task; CoC Defect detection task; A value Symbol cancelation; CoC Line crossing task; CoC Reading numerals
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