Influence of the radial and vertical dimensions on lateral neglect

The influence of radial (near-far) and vertical (upper-lower) dimensions on lateral visuo-spatial neglect was studied using two horizontal line-bisect ion tasks (one motor and one perceptual). A group of 15 patients with negle ct and a group of 14 right-brain damaged patients without neglect were exam ined. This latter group was used to define the range of variability in line -bisection performance that was independent of neglect. For the radial dime nsion, some neglect patients showed greater errors in far space than in nea r space (for both stimuli presented in the upper and lower space). Fewer pa tients showed the opposite pattern (i.e., greater errors for near-space sti muli). These near-far asymmetries were present for both the motor and perce ptual, conditions and showed a good degree of intra-individual consistency. This finding contradicts the hypothesis that the motor component is critic al for yielding such asymmetry. For the vertical dimension, the results ind icated that neglect patients make more bisection errors for lower-space sti muli than for upper-space stimuli. This vertical asymmetry was nearly alway s confined to stimuli in near space. Asymmetries along the vertical dimensi on were present for both perceptual and motor conditions, although intra-in dividual consistency was low. When perceptual and motor conditions were dir ectly compared, several neglect patients showed greater errors in the perce ptual than in the motor task.