Otolithic and Extraocular Muscle Proprioceptive Influences on the Spatial Organization of the Vestibulo- and Cervico-Ocular Quick Phases

Abstract

The cervico-ocular reflex (COR) was studied alone or in combination with the vestibulo-ocular reflex (VOR) in the rabbit. Step stimulations of the body with respect to the fixed head induced small slow compensatory responses followed by large compensatory quick phases (QP). These responses remained aligned with the horizon at different head pitch angles. The QP reorientation in space was due to the gravity influence on the otolithic receptors. The vestibular induced QPs exhibit a similar pattern. Because of this reorientation, the reduction of the amplitude of the vestibular induced QPs, due to the addition of the COR, was maintained even at different static head positions. The electrolytic lesion of the ophthalmic branch of the trigeminal nerve deeply affected the space orientation of the COR. In particular, the cervically induced compensatory QPs of the eye ipsilateral to the lesion showed a remarkable variability of their trajectories and they lost space reorientation. These findings suggest that the coordinate system controlling the QPs is influenced by signals originating from both head position in space and eye position in the orbit.

Functional Recovery after Extra-ocular Muscle Deafferentation in the Rabbit

“…As previously demonstrated (10,11), VOR slow phases do not appear to be directly controlled by proprioceptive position signals. On the contrary, QP generating mechanism requires proprioceptive signals for coding QP velocity and trajectory parameters.…”

“…The spatial orientation of HVOR slow and quick phases was studied by measuring the velocity of the horizontal and vertical components of the eye re- As observed in previous works (10,11), immediately after the lesion of the semilunar ganglion, slow phases appeared almost unaffected. On the contrary, QPs showed a decrease in peak velocity from 90% to 50% and a deviation of trajectories of 5 -20° (Fig.…”

“…In addition, it has been ascertained that modi cation of the EOM afferent signal directly alters several performances of ocular motility, such as eye stability (3,6) and VOR characteristics (7 -9). More recent researches (10,11) have measured both horizontal and vertical components of eye position, and have demonstrated that in rabbits and lambs EOM deafferentation has a strong in uence on VOR quick phases (QPs). In particular, QP trajectories, in the rabbit, appear to be spatially disorganized after a lesion of the semilunar ganglion that contains the somata of the rst order proprioceptive neurons of the EOMs (12).…”

“…In particular, QP trajectories, in the rabbit, appear to be spatially disorganized after a lesion of the semilunar ganglion that contains the somata of the rst order proprioceptive neurons of the EOMs (12). The time course of VOR impairment has not been reported because some experiments have been performed on acute animals (10,11) and others have addressed only long-term normalization of function (9). Thus, the present research has the aim to extend the studies on the role of EOM proprioception on ocular motility by analysing the functional recovery after partial unilateral lesion of EOM proprioceptive afferents.…”

Role of the cervico-ocular reflex in the “flying” pigeon: Interactions with the optokinetic reflex

“…The characteristics of this gain are similar to those found in most species. The fast phases appear to be triggered in the compensatory direction in most species, as observed in the chameleon (Gioanni et al, 1997), rat and cat (Fuller, 1980), rabbit (Fuller, 1980;Barmack et al, 1981Barmack et al, , 1989Pettorossi et al, 1997), and guinea pig (Mirenowicz & Hardy, 1992). The polarity of the COR is generally defined with respect to the relative head movement (by considering that the head is rotating relative to a fixed trunk rather than the trunk is rotated relative to a fixed head).…”