Cervico-Ocular Reflex After Labyrinthine Damage
The effects of peripheral vestibular damage on eye motility consist of both eye nystagmus and impairment of vestibulo-ocular reflexes (VOR’s). Although the compensation of nystagmus is complete in the light (Schaefer and Meyer 1973), the recovery of the VOR was less than complete after unilateral and bilateral labyrinthine lesions (Baarsma and Collewijn 1975; Barmack and Pettorossi 1981; Maioli et al. 1983; Paige 1985). In the rabbit, the gain of the VOR remained much less than half of normal after hemilabyrinthectomy (HL) (Baarsma and Collewijn 1975; Barmack and Pettorossi 1981). Thus, in the presence of a labyrinthine lesion a large deficit would remain in the rabbit’s ability to maintain a stable retinal image unless other reflexes may reduce it through a substitution process. Since the optokinetic reflex (OKR) slightly improved the oculomotor reactions (Baarsma and Collewijn 1975) the cervico-ocular reflex (COR) could play a role in the functional recovery. In fact it has been demonstrated that in normal rabbits the COR (1) contributes to maintain gaze stability; (2) sets the range of reflex eye movements toward a more compensatory position depending on the head-body angle (Meiry 1971; Barnes and Forbat 1979; Barmack et al. 1981; Barmack et al. 1985); and (3) undergoes plastic changes in the presence of labyrinthine lesions (Dichgans et al. 1974; Kasai and Zee 1978; Baker et al. 1982). The COR is agonistic to VOR and OKR in compensating for horizontal head displacements by enhancing the gain and decreasing the phase lead of HVOR at low frequencies of stimulation (0.005x0.05 Hz) (Barmack et al. 1981).
KeywordsSemicircular Canal Ocular Response Compensatory Position Cervical Stimulation Secondary Vestibular Neuron
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