Dynamics of changes in operant reflexes in rats after transection of the corticospinal tract and removal of the sensorimotor region of the cerebral cortex.

Prior unilateral transection of the bulbar pyramid facilitated recovery of operant reflexes and compensatory processes occurring after removal of the ipsilateral sensorimotor cortex in rats. This increase in corticofugal plasticity was absent when only the sensorimotor cortex was removed. This phenomenon is explained by switching of descending influences to the corticorubrospinal system via the following loop: corticobulbar projection--red nucleus--lower olive--cerebellum--thalamus--cortex. A general property of this phenomenon is that prior lesioning of the peripheral part of the descending spinal projection acquires anticipatory signal value for mobilizing the compensatory abilities of the brain with the aim of recovering from the deficit of the central branch of the system.