Changes in sensory inattention, directional motor neglect and "release" of the fixation reflex following a unilateral frontal lesion: a case report

Abstract

We recorded eye movements to and away from visual stimuli from a patient with left-sided neglect following a right frontal infarct in order to determine (a) whether and to what extent his neglect was due to sensory inattention and directional motor neglect and (b) whether he had difficulty suppressing inappropriate eye movements to visual stimuli ("release" of visual grasp) as his sensory inattention declined. In the first testing session, conducted 5 days following his stroke, he often failed to move his eyes when a stimulus on the left required a rightward eye movement, but he consistently moved his eyes to a stimulus on the right. Thus, he showed contralateral but not ipsilateral sensory inattention. Initially, he also was impaired in making leftward eye movements when right stimuli were presented. Thus, he also showed a directional motor neglect. In subsequent tests, his left-sided sensory inattention as defined above decreased, and was no longer present three weeks following his stroke, nor in a follow-up test conducted almost 6 months following this stroke. In contrast, his directional motor neglect, as defined above, was still present in the follow-up test. As his left-sided sensory inattention declined, his tendency to move his eyes incorrectly to stimuli on the left side (the side contralateral to his lesion) when these stimuli required eye movements to the right became stronger ("release" of visual grasp); he continued to show this strong tendency in the test conducted almost 6 months following his stroke.