Analysis of left unilateral spatial neglect with a non-visual sensory-motor task

An experiment was conducted to analyze the space-movement processes which unilateral spatial neglect (USN) patients manifested. Three kinds of movement features were tested which were reported in previous studies; (a) general coarse response tendency, (b) hypokinesia in the disordered spaceside, and (c) more frequent response toward the normal space-side. Five left USN patients with right brain damage were compared with five non-USN right brain damaged patients, and five normal controls. As an experimental movement task, a non-visual movement reproduction with regard to kinesthetic sensory modality was adopted. Subjects were blindfolded and asked to reproduce the criterion-movement (length of 10 cm) toward right hand side in space. Three different experimental spaces were used in relation to the subject's body positions; ‘left space (range from left shoulder to median line)', ‘right space (from median line to right shoulder)', and ‘right-outside space (outside of right shoulder)'. The criterion-movement was presented to the subjects, and then they reproduced the movement in either one of these three spaces. Generally, the left USN patients reproduced movements with more errors and less accuracy when the execution side was in the ‘left space'. The results confirmed the observation that left USN patients showed more frequent response toward the right hand side direction in the ‘left space'. The left USN patients with lesions in frontal and/or basal ganglia regions showed larger errors in this task compared to the left USN patient whose lesion is localized in the parietal region in the right hemisphere.