'Vestibular compensation: neural plasticity and its relations to functional recovery after labyrinthine lesions in frogs and other vertebrates

Abstract

Removal of the labyrinthine organs on one side is followed by a number of severe postural and dynamic reflex deficits. Some of these deficits, in particular the posture of head and body, are normalized again over a period that varies strongly between species. Other, more persistent motor deficits are substituted, e.g. by the saccadic system. This partial normalization of the function is accompanied by changes in response properties of the central vestibular neurons on the operated side. Available evidence suggests the occurrence of reactive synaptogenesis in cat and frog. In the latter species the synaptic efficacy of commissural vestibular connections increases and the metabolic activity of central vestibular neurons on the operated side recovers post-operatively. The onset of both changes, however, is delayed by about 30 days, which is too late to be causally related with the initial, rapid period of postural recovery in frog and cat. In frogs additional, early (7-15 days p.o.) and late (45-60 p.o.) synaptic changes were detected in the branchial spinal cord. These multiple changes survive the isolation of the spinal cord and must be propriospinal in origin. Selective lesions of individual vestibular nerve branches indicate that inactivation of utricular inputs is a sufficient and necessary condition to provoke postural deficits and early spinal changes similar to those after hemilabyrinthectomy. Therefore, a close correlation between spinal plasticity and postural recovery is indicated. In essence, the elimination of vestibular afferent inputs results in a series of behavioral distortions that are partially normalized by a multitude of synaptic mechanisms at distributed anatomical sites over different periods of time.

Walking performance of vestibular-defective patients before and after unilateral vestibular neurotomy

“…This function could be more independent of the vestibular cues [16]. The data also point to the permanent role of vision in compensating the vestibularly induced deficits (see references [12,29,39] for reviews), including the spatial orientation impairments. The lateral deviation towards the lesioned side in patients tested EC after UVN was higher for the normal locomotion speed.…”

Physiological changes of premotor nonspiking interneurons in the central compensation of eyestalk posture following unilateral sensory ablation in crayfish

“…Changes in the shape of synaptic potentials have been reported in the vestibular compensation process of frogs (Dieringer andPrecht 1977, 1979a,b;Galiana et al 1984), although the physiological mechanism underlying those changes remains unknown. In the present study, we found that the peak amplitude of excitatory and inhibitory PSPs as well as their rise rate and half decay time showed complex changes depending on the polarity and laterality (Fig.…”

“…However, this posture is gradually normalized to restore the original symmetrical posture. The posture compensation following partial destruction of the geotactic sense organ has been well known in many animals including vertebrates (Smith and Curthoys 1989;Darlington and Smith 2000;Dieringer 1995) and invertebrates (Schöne 1954(Schöne , 1971Sakuraba and Takahata 1999), the time required for the recovery depending on the animal species, ranging from several hours (rat) to weeks (rabbit). The neuronal mechanisms underlying the behavioral recovery, however, largely remain elusive.…”

Nitric oxide synthase in the frog cerebellum: Response of Purkinje neurons to unilateral eighth nerve transection

“…As regards more specific studies on the effects of vestibular neurectomy in the frog, since the early 1970s Dieringer has studied the vestibular nucleus, spinal cord, and cerebellum. Dieringer (1995) reported the sole finding on the response of Purkinje neurons to stimulation of the eighth nerve; however, no mention was made of the Purkinje cells of the corpus cerebelli or vestibulocerebellum.…”

“…In the extensive literature on vestibular compensation (for review, see Dieringer, 1995), the frog has also been considered as a neurobiological model. The involvement of Purkinje cells following the stimulation of the eighth nerve has also been reported (Dieringer and Precht, 1979a, b).…”