Patterns of eye movements during cancellation tasks in stroke patients exhibiting hemispatial neglect

To investigate whether hemispatial neglect arises due to an information sampling deficit or impaired processing of information on the left we measured eye movements of stroke patients whilst they completed a sub-set of the Behavioural Inattention Test (BIT; Wilson et al., 1987, Behavioural Inattention Test. Suffolk, UK: Thames Valley Test Company) over three sessions. Participants who initially demonstrated left neglect in star and letter cancellation tasks exhibited a marked sampling deficit, with fewer visits made and less total time spent on the far left region of the stimulus. In the later testing sessions, a different pattern of eye movements emerged, with compensatory eye movements being made. The amount of time spent on the left increased and gaze durations were longer in the far left region compared with the other regions. This suggests that, although participants over time could sample information from the neglected region, the acquisition and processing of that information was impaired. Furthermore, behavioural measures (from the letter cancellation task) showed that, despite fixations on the left of the stimulus in the later testing sessions, neglect was still present, indicating a processing deficit. Overall, these results demonstrate neglect can arise due to both information sampling and information processing deficits.