Prism adaptation power on spatial cognition: Adaptation to different optical deviations in healthy individuals

The main objective of the present study was to determine the minimal optical deviation responsible for cognitive after-effects in healthy individuals and to explore whether there was a relationship between the degree of optical deviation and cognitive after-effects. Therefore different leftward optical deviations (8 degrees, 10 degrees and 15 degrees) were used in three different groups of healthy participants. Sensorimotor after-effects (evaluating the visuo-manual realignment) were assessed using an open-loop pointing task and cognitive after-effects (evaluating changes in spatial representation) were assessed using manual and perceptual (landmark) line bisection tasks. Results revealed that exposure to 8 degrees, 10 degrees and 15 degrees optical shifts produced sensorimotor after-effects. In contrast, the occurrence of cognitive after-effects depended on the optical deviation. Adaptation to an 8 degrees leftward optical deviation did not produce cognitive after-effects. Adaptation to a 10 degrees leftward optical deviation was responsible for after-effects in the manual line bisection task only. Adaptation to a 15 degrees leftward optical deviation produced after-effects in both the manual and perceptual line bisection tasks. All cognitive after-effects were rightward and were similar to mild, neglect-like manifestations. Both sensorimotor and cognitive after-effects were correlated with the degree of optical deviation. Our results are of methodological and theoretical interest to those interested in sensorimotor plasticity and spatial cognition. (c) 2015 Elsevier Ireland Ltd. All rights reserved.