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°, 10° and 15°) 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°, 10° and 15° optical shifts produced sensorimotor after-effects. In contrast, the occurrence of cognitive after-effects depended on the optical deviation. Adaptation to an 8° leftward optical deviation did not produce cognitive after-effects. Adaptation to a 10° leftward optical deviation was responsible for after-effects in the manual line bisection task only. Adaptation to a 15° 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.