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A Ferraresi

Publications and source records attributed to A Ferraresi.

23 records · Page 2Linked to original sources
PubMed1989

Interactions of cervico-ocular and vestibulo-ocular fast-phase signals in the control of eye position in rabbits.

1. Eye movements in unanaesthetized rabbits were studied during horizontal neck-proprioceptive stimulation (movement of the body with respect to the fixed head), when this stimulation was given alone and when it was given simultaneously with vestibular stimulation (rotation of the head-body). The effect of neck-proprioceptive stimulation on modifying the anticompensatory fast-phase eye movements (AFPs) evoked by vestibular stimulation was studied with a 'conditioning-test' protocol; the 'conditioning' stimulus was a neck-proprioceptive signal evoked by a step-like change in body position with respect to the head and the 'test' stimulus was a vestibular signal evoked by a step rotation of the head-body. 2. The influence of eye position and direction of slow eye movements on the occurrence of compensatory fast-phase eye movements (CFPs) evoked by neck-proprioceptive stimulation was also examined. 3. The anticompensatory fast phase (AFP) evoked by vestibular stimulation was attenuated by a preceding neck-proprioceptive stimulus which when delivered alone evoked compensatory slow-phase eye movements (CSP) in the same direction as the CSP evoked by vestibular stimulation. Conversely, the vestibularly evoked AFP was potentiated by a neck-proprioceptive stimulus which evoked CSPs opposite to that of vestibularly evoked CSPs. 4. Eccentric initial eye positions increased the probability of occurrence of midline-directed compensatory fast-phase eye movements (CFPs) evoked by appropriate neck-proprioceptive stimulation. 5. The gain of the horizontal cervico-ocular reflex (GHCOR) was measured from the combined changes in eye position resulting from AFPs and CSPs. GHCOR was potentiated during simultaneous vestibular stimulation. This enhancement of GHCOR occurred at neck-proprioceptive stimulus frequencies which, in the absence of conjoint vestibular stimulation, do not evoke CSPs.

Animals↗
PubMed1987

Vestibular contribution to the orientation of cervico-ocular reflex in rabbit.

In the rabbit the cervico-ocular reflex (COR) helps to maintain the gaze stability during passive head displacements, by increasing the gain and decreasing the phase lead of low frequency vestibular responses and by diminishing in amplitude the anticompensatory vestibular fast phases. These cervical influences appear only for horizontal stimulations, while they are scarce or absent in the vertical and sagittal planes. Ocular responses to horizontal body displacements are oriented in the horizontal plane and remain in the same plane when the head is statically pitched at various degrees, in spite of the directional changes in the extraocular muscle (EOM) lines of force with respect to space. Tension recordings from the EOMs show that the oculomotor system is differently activated depending upon the degree of head inclination. This change in the EOM activation is not observed when the body, instead of the head, is pitched. Furthermore, after bilateral labyrinthectomy (BL) the cervico-ocular responses lose their appropriate directionality. It is concluded that the information for determining the plane of the eye movements during cervical stimulations does not originate from the neck proprioception but is provided by the otolithic receptors.

Animals↗
PubMed1986

Comparative actions of four aminoglycoside antibiotics on the vestibular function in guinea-pigs.

This study was designed to assess the actions of 4 representative aminoglycoside antibiotics on the vestibular functions in guinea-pigs as evidenced by the measurements of the vestibulo-ocular reflex (VOR) either in the horizontal (HVOR) or in the vertical plane (VVOR). VOR responses were evaluated over a wide range of stimulation frequencies prior to and after 10 and 18 days of a multiple dose regimen with dibekacin (150 mg/kg), gentamicin (100 mg/kg), netilmicin (150 mg/kg), tobramycin (100 mg/kg) or saline. All drugs or saline were given intramuscularly twice a day. The labirinthine function was found to be differently impaired by drug administration. Gentamicin induced severe vestibular impairment, which had early onset. Dibekacin greatly reduced all VOR responses, but changes occurred after a longer period of time. Tobramycin and netilmicin induced slight vestibular impairment only after 18 days of treatment. Tobramycin affected both HVOR and VVOR responses at the high frequencies, while netilmicin impaired only the HVOR. Histological examination of vestibular epithelia was conducted by using the Scanning Electron Microscope (SEM). Gentamicin and dibekacin greatly damaged both the cristae of semicircular canals and utriculi, structures which are involved in the generation of VOR responses. Conversely, tobramycin provoked damages only in the cristae of semicircular canals and netilmicin did not affect the vestibular sensory epithelia. These findings indicate that each aminoglycoside produces characteristic actions on the vestibular function which depend on the damage distribution in the labirinthine structures. Among the aminoglycoside examined, netilmicin appears to possess the lowest potential for producing impairment of the vestibular function.

Aminoglycosides↗
PubMedDate not supplied

Difference in quick phases induced by horizontal and vertical vestibular stimulations: role of the otolithic input.

Quick phases (QPs) induced by horizontal and vertical sinusoidal vestibular stimulations were studied in rabbits, cats, and humans. In all the animals, large and frequent horizontal QPs were observed following yaw stimulation in prone position. By contrast, QPs were almost absent during roll stimulation in rabbits, and they were small and oblique during pitch stimulation in cats and humans. As a result of these differences, the range of gaze displacement induced by vestibular stimulations was greater in the horizontal plane than in the vertical one. We also found that the trajectory of the QPs in rabbits was kept horizontal even when the yaw rotation was off vertical axis of +/- 45 degrees in the sagittal plane. Moreover, in the rabbit, the rare horizontal QPs induced by roll stimulation did not change their orientation at various pitch angles of roll stimulation axis. The QPs were also analyzed following roll stimulation of the rabbit in supine position. In this condition, in which the otolithic receptors were activated in the opposite way compared to prone position, large vertical QPs were elicited. We concluded that these results provide evidence that the otolithic signal plays a role in controlling occurrence and trajectory orientation of the QPs.

Adult↗