Directional hypokinesia and hemispatial inattention in neglect

Subjects with neglect of left hemispace may err to the right when bisecting lines. This error has been attributed either to a directional hypokinesia (failure to execute movements fully in or towards the contralateral hemispace) or to a failure to attend to or represent sensory information. Four subjects with neglect were tested on a line bisection task in which these two hypotheses were differentiated by preventing direct viewing of the line and instead using a video camera and monitor, each of which could be moved independently into right or left hemispace. The performance of 2 subjects was consistent with the predictions of the directional hypokinesia hypothesis; the performance of the other 2 subjects was consistent with the attention-representation deficit hypothesis. These data suggest that both a directional hypokinesia and an attention-representation deficit may each be a primary determinant of neglect.