Humans are able to stabilize the images of moving targets on the retina by means of smooth pursuit eye movements. After the pontine level, all smooth pursuit pathways pass through the cerebellum. Previous animal studies gave evidence that two specific lesion sites within the cerebellum cause smooth pursuit disorders: those of the flocculus/paraflocculus and the vermis including lobule VI, VII, ...

Dynamic motion simulators cannot provide the same stimulation of sensory systems as real motion. Hence, only a subset human senses should be targeted. For providing vestibular stimulus, an automatic bodily function vestibular–ocular reflex (VOR) can objectively measure how accurate simulation is. This requires model ocular response to enforced accelerations, attempt create which is shown in thi...

Alexander's Law states that the slow-phase velocity of the nystagmus caused by unilateral vestibular lesion increases with gaze in the beat direction. Two studies have shown that this gaze effect is generalized to the nystagmus caused by unilateral cold water irrigation. This indicates that the gaze effect is not the result of central changes associated with a peripheral lesion but rather becau...

BACKGROUND This study compared vestibulocollic reflex and vestibulo-ocular reflex functioning in subjects with and without human immunodeficiency virus. It also described test results throughout progression of the disease and compared the results of human immunodeficiency virus positive subjects who were receiving antiretroviral therapies with those not receiving this treatment. METHODS Subje...

The Justification Hypothesis (JH; Henriques, 2003) is a basic, general, and macro-level construct that is highly compelling. However, it needs greater specification (i.e., justification) regarding what it is, how it might be operationalized and measured, and what it does and does not predict in the real world. In the present analysis, the act of "justification" is conceptualized as the ongoing ...

The fixation reflex is an important representative of orienting (targeting) reflexes. In the cat with the brainstem transected at the pretrigeminal level the fixation reflex is easy to investigate for the following reasons: (a) all sensory inputs to the isolated cerebrum of the pretrigeminal cat are eliminated, except for visual afferents, (b) the isolated cerebrum is continuously awake, (c) th...

The oculomotor integrator is usually defined by the characteristics of decay in gaze after saccades to flashed targets or after spontaneous gaze shifts in the dark. This property is then presumed fixed and accessed by other ocular reflexes, such as the vestibuloocular reflex (VOR) or pursuit, to shape motoneural signals. An alternate view of this integrator proposes that it relies on a distribu...

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (approximately 200 ms), high-acceleration (0.4-1.4g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 +/- 5 ms at 15-cm and 20 +/- 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head v...

The primary purpose of the vestibulo-ocular reflex (VOR) is to allow clear vision during walking and other faster movements. These occur at frequencies greater than 1 Hz. Other oculo-motor systems, such as smooth pursuit and optokinetic, respond poorly at these higher frequencies. The VOR functions as the major oculo-motor system responsible for maintaining visual fixation during faster head mo...