Visual-motor adaptation. Quantitative demonstration in patients with posterior fossa involvement
G. M. Gauthier, J. M. Hofferer, W. F. Hoyt and L. Stark
Short-term visual-motor adaptation to magnifying spectacle lenses was
studied in normal subjects and in patients with nonacute posterior fossa
lesions. When normal subjects, looking through magnifying lenses, pointed
open loop to targets without viewing their hands, they initially
underestimated the distance (magnification effect). After a 20-minute
close-loop training or adaptation exposure period during which they viewed
the performance of their hands, a modified visual-motor scheme evolved,
compensating for about half of the lens-induced pointing error (adaptation
effect). Removal of the lenses after adaptation caused open-loop,
overshooting pointing errors (adaptation after-effect). Four patients with
remission of cerebellar signs showed normal visual-motor adaptive
performance, evidence of ability to recalibrate gain. One patient with
persisting cerebellar ataxia was unable to recalibrate gain during
close-loop visual-motor training. His history of transient palatal
myoclonus implicates a role for the cerebellar-olivary system in
calibration of visual-motor gain.
