Some of the behavioural tests, as the Behavioral Inattention Test, evaluate the performance on daily activities such as phone dialling, coin sorting, or map navigation, in addition to performance on conventional cancellation tasks. However, the long duration of these tests can make them tiresome for many patients and time-consuming for clinicians. The need for a therapist during the test and its psycholinguistics requirements could also prevent their widespread use. Eye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. This information can be used to infer levels of presence, attention, focus, drowsiness, consciousness or other mental states, which is of special interest to research on the visual system, in psychology, and human computer interaction.
To explore the potential of this technology for assessing unilateral spatial neglect in stroke survivors we performed a pilot study with a 65-year-old woman with an ischemic focal lesion in the non-dominant cerebral hemisphere who was admitted to our facility.3 Symptomatology included severe left hemiparesis and pronounced unilateral spatial neglect syndrome. The woman and a healthy age-matched woman were enrolled in an eye tracking study where they were required to look for 60 seconds an image of the Behavioral Inattention Test and name the items present in it. Gaze parameters of both subjects were recorded and heat maps were estimated as superimposed distributions of eye fixations. In contrast to the healthy subject (see left column), who revealed distributed fixations in all the image, the stroke survivor presented an absence of fixations in the left side of the image (see right column), thus confirming the diagnosis and illustrating the behavioral complications that affected her everyday functioning.
Benefits of this protocol could be threefold: first, it provides qualitative (visual) but also quantitative (fixation times, gaze patterns, etc.) information; second, it is easy to administer and not time-consuming; and third, no specific cognitive or psycholinguistic condition is required to patients. In addition, low-cost eye-tracking devices are available for $100. Even though these results are preliminary and the study focuses on the visual input and the peripersonal space, it could be a potential tool to provide relevant information about the deficits and their functional consequences.