Evidence from visuo-motor adaptation for two partially independent visuo-motor systems

There is behavioral and neurological evidence for the idea that visual processing of spatial information with respect to the subject (egocentric) and visual processing of spatial information with respect to an external frame of reference (allocentric) is functionally and neurologically distinct. However, it is unknown how these two different types of visual spatial information are mapped onto movement parameters. The experiments reported here used a visuo-motor adaptation paradigm to test if subjects rely on different visuo-motor mappings in tasks that require them to move their hand based on egocentric or allocentric visual information (Fig.1). In an adaptation phase, subjects (n=9) received distorted visual feedback about their hand movements. Feedback was rotated 17 degrees with respect to movement direction and stretched 110% with respect to movement amplitude. In a testing phase (no visual feedback), we measured how behavior changes in response to the distorted visual feedback. We used two tasks in testing and adaptation that required processing of egocentric and allocentric visual information (Fig.1). The results show, that behavioral changes are significantly larger when the same task is used during testing and adaptation, compared to when the task is switched (Fig.2). The findings suggest that human observers have two partially independent visuo-motor systems that rely on different types of visual spatial information.