Vestibular compensation in the lamprey.

Vestibular compensation, i.e. recovery after unilateral labyrinthectomy (UL) in the lamprey (a lower vertebrate, Cyclostome), as well as different means of promoting the compensation, is described. UL results in a loss of equilibrium and rotation during swimming which is compensated in about 60 days. The deficit can, however, be immediately abolished by applying asymmetrical tonic visual or vestibular input (electrical stimulation of the optic or vestibular nerve, illumination of one eye, removal of one eye). In addition, asymmetrical visual input promotes plastic changes underlying the vestibular compensation. The compensation is discussed in relation to the neuronal network responsible for postural control in the lamprey and identified in our previous studies.