Sensorimotor adaptation of saccadic eye movements.

Sensory-motor adaptation mechanisms play a pivotal role in maintaining the performance of goal-directed movements. The saccadic system, used to explore the visual environment through fast and accurate shifts of the eyes (saccades), is a valuable model for studying adaptation mechanisms. Significant progresses have been recently made in identifying the properties and neural substrates of saccadic adaptation elicited by the double-step target paradigm. Behavioural data collected in healthy and brain-damaged subjects, and neurophysiological data from non human primates, will be reviewed in an attempt to build a coherent picture of saccadic adaptation mechanisms. Emphasis will further be put on the contextual factors of saccadic adaptation, and on the link between adaptive changes of oculomotor commands and visual perception. It will be shown that saccadic adaptation relies on multiple mechanisms according to experimental contexts, time-scales, saccade categories, and direction of adaptive changes of saccade amplitude (shortening versus lengthening). Taking into account this complexity will be a key toward a comprehensive understanding of the physiopathology of saccadic adaptation and toward the development of possible rehabilitation procedures.