Locomotor dysfunction after surgical lesions in the unilateral vestibular nuclei region in squirrel monkeys.

The present experimental results in squirrel monkeys indicated that the performance of psycho-physically advanced locomotor task (squirrel monkey rail test) was severely impaired after the placement of the medium to relatively large surgical lesions in the unilateral vestibular nuclei area, and therefore, confirmed that this brain-stem structure is essential for the signal relay and/or input coordination. The severest locomotor disability was found 10-14 days after the surgery; thereafter, squirrel monkeys showed very gradual and only limited degree of performance recovery. The post-ablative performance levels were no better than 1/5 of their pre-ablative performance levels.