Adaptation of saccadic and vestibulo-ocular systems after extraocular muscle tenectomy.

Adaptation of saccadic magnitude and vestibulo-ocular reflex gain (VOR) was examined in six monkeys that had undergone a tenectomy of the medial and lateral recti of one eye. After the tenectomy, when the normal eye was patched, a conjugate increase in saccadic magnitude and VOR was observed in both eyes. Subsequent unpatching resulted in selective (nonconjugate) changes in the two eyes such that control values of saccadic magnitude and VOR gain were eventually reestablished in both eyes. Evidence that this return to normal was mediated by a selective adaptation of the neural innervation to one eye was provided by the following observations: (1) saccades in the normal eye were of a lower peak velocity and longer duration after normalization than prior to the tenectomy; and (2) repatching the tenectomized eye after normalization produced a selective return of deficits in that eye over a period of a few days. Thus, the saccadic and vestibulo-ocular systems can be adapted in both a conjugate and a selective or nonconjugate fashion.