Shifting Spatial Neglect With Repeated Line Bisections: Possible Role of Lateralized Attentional Fatigue

Many patients who have signs of neglect immediately after a right hemisphere stroke remain disabled even when they improve on tests of neglect. Few patients are tested for attentional persistence and fatigue despite their importance in many instrumental activities. To investigate whether stimulus repetition might alter the allocation of attention, we repeatedly tested a patient 16 weeks after she developed hemispatial neglect from a right hemisphere stroke.

During each of three testing sessions given in 1 day, we asked the patient to bisect 90 lines of two lengths, presented in 30-trial blocks in three locations: left, center, and right of her midsagittal plane, partially counterbalanced across sessions. We adjusted multiple regression analyses and analysis of variance as well as post hoc regression and t tests for persistence in the repeated measures using variance-sample size analysis to estimate self-similarity, a measure related to the fractal correlation dimension.

In each session, the patient's line bisections revealed transient leftward bias in her left peripersonal space, and constant rightward bias in her right peripersonal space. Her leftward bias shifted to a rightward bias over repeated trials in her left space.

The patient's left-to-right shift with repeated trials suggests either fatigue from an attempted compensation for leftward inattention or habituation of a contralesional spatial attentional attraction, revealing contralesional left-sided neglect in both the left and right spaces. Future studies are needed to learn if other patients show similar or different deficits with repetition, and how best to treat them.