Role of the visual input in recovery of function following unilateral vestibular lesion in the goldfish. I. Short-term behavioural changes.
Vestibular compensation, i.e. the partial or complete recovery of function following lesion of a labyrinth, has been suggested to be based on a multisensory substitution process involving vestibular, visual and somatosensory information. Teleost fish would seem ideal subjects for testing this proposal, because equilibrium orientation in the intact animal is largely under the bimodal control of the vestibular and visual systems. The role of the visual input in the compensation of behavioural deficits elicited by hemilabyrinthectomy (HL) was studied in goldfish maintained over the first two postoperative hours under different lighting conditions. HL caused severe postural and locomotory symptoms, which were the same or similar under all lighting conditions. The rate at which the various deficits disappeared, however, was dependent not only on the presence of light but also on its direction of incidence. Animals maintained under overhead illumination reached the criterion of successful compensation (completion of 5-min continuous and unimpaired swimming) within 10 min, whilst under unilateral illumination (90 degrees to the vertical) the time to criterion was significantly increased; animals exposed to illumination from below or infra-red illumination showed little or no signs of compensation up to 2 h after HL. It is concluded (1) that the immediately postoperative stage of vestibular compensation in the goldfish represents an integral part of the recovery process, within which all observable deficits can be compensated with remarkable rapidity; and (2) that the visual input is both necessary and sufficient for the compensation of the immediately postoperative deficits. We term this early stage of recovery the 'acute' phase and consider it to be based on a visual substitution process, whereby the missing labyrinthine input to the (partially) deafferented vestibular neurons is functionally replaced by visual afferents.
Burt
A
A
Brain Research Institute, University of Bremen, F.R.G.
Flohr
H
H
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology* / Q000528:radiation effects; D004777:Environment; D006054:Goldfish / Q000502:physiology*; D007259:Infrared Rays; D008027:Light; D009475:Neurons, Afferent / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*