Cognitive bias induced by visuo-motor adaptation to prisms: a simulation of unilateral neglect in normal individuals?

Unilateral neglect has been recently shown to be improved following a short period of adaptation to wedge prisms. The present study investigates whether visuo-motor adaptation can generate a bias in normals on line bisection tasks classically used to assess unilateral neglect. Our results show that adaptation to left-deviating prisms induces a stronger rightward bias for the perceptual than the motor line bisection task. This bias is in the same direction as the one observed in unilateral neglect. No significant effect is produced by adaptation to right-deviating prisms. Our data confirm that the plasticity of inter-sensory and sensori-motor coordinations affects higher levels of space representation. These asymmetric results may reflect the inherent bias of the brain's structural organisation and provide an empirical explanation for the left-sided predominance of unilateral neglect.