[Relearning and critical postoperative period in the restoration of nerve function. Example of vestibular...

The role of sensorimotor activity in the recovery process after unilateral vestibular neurectomy was studied on cats and monkeys using behavioral and electrophysiological methods. It was analyzed by comparing the time-course of the recovery of posture, locomotion and equilibrium function in animals which remained free after surgery in their usual environment (unrestrained group) to others which were submitted to a postoperative sensorimotor restriction (restrained group). This sensorimotor restriction was applied at different postoperative times; the effects of short and long-lasting restrictions were also studied. Results showed that the functional recovery develops in active animals only, i.e. when they can use all available information elicited by an active sensorimotor exploration. It is blocked and delayed in the restrained group, the postoperative disorders being reduced much later when a long-lasting restriction is used. It is also demonstrated that the functional recovery is better and faster in animals having an early sensorimotor activity. It is concluded that vestibular compensation resembles a sensorimotor relearning process requiring the activity of the subject, and that a postoperative critical period may exist in functional recovery which may be crucial for achieving well-or maladapted behavior. The clinical implications of these findings are presented in the discussion as some general principles able to stimulate reflexions and improve the postoperative training methods.