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The firing behavior of 51 non-eye movement related central vestibular neurons that were sensitive to passive head rotation in the plane of the horizontal semicircular canal was studied in three squirrel monkeys whose heads were free to move in the horizontal plane. Unit sensitivity to active head movements during spontaneous gaze saccades was compared with(More)
The influence of the efferent vestibular system (EVS) upon the background discharge and response dynamics of horizontal semicircular canal afferents was examined in the toadfish. In one set of experiments the EVS was activated using a behavioral paradigm; in the second, electrical shocks were applied to the efferent vestibular nucleus in the brain stem. The(More)
In the alert monkey (Macaca fascicularis) vestibular nuclei neurons and eye movements were recorded during sinusoidal optokinetic stimulation in the horizontal plane at frequencies between 0.02–3.3 Hz. Maximal stimulus velocity was generally kept constant at 40 deg/s, except for frequencies above 1 Hz. Eye movements showed a nystagmuslike pattern up to 0.2(More)
Mechanical occlusion of one or more of the semicircular canals is a surgical procedure performed clinically to treat certain vestibular disorders and used experimentally to assess individual contributions of separate canals and/or otoliths to vestibular neural pathways. The present experiments were designed to determine if semicircular canal afferent nerve(More)
The response dynamics of 66 primary afferents of the horizontal semicircular canal were studied in the toadfish using sinusoidal, rotational stimuli from 0.001-10 Hz at amplitudes of 5-100 degrees/sec. Twelve afferents were also tested to constant velocity trapezoids. Responses to sinusoids were used to classify afferents into 3 broad groups: (1) low-gain(More)
The consequence of exposure to microgravity on the otolith organs was studied by recording the responses of vestibular nerve afferents supplying the utricular otolith organ to inertial accelerations in four toadfish, Opsanus tau, sequentially for 5 days following two National Aeronautics and Space Administration shuttle orbital flights. Within the first day(More)