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Query: UMLS:C0028738 (nystagmus)
 7,431 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It was previously proposed that a linkage between the optokinetic system and the stereoscopic system in higher mammals serves to allow these animals to selectively stabilize those parts of the visual scene which lie in the plane of convergence as the animals move forward in a three-dimensional world (Howard and Ohmi, 1984). A new procedure is now described by which OKN gain can be measured as a function of the binocular disparity of the stimulus. With vergence locked on a vertical line, the gain of the slow phase of vertical optokinetic nystagmus (OKN) was recorded in four human subjects as the binocular disparity (stereo depth) of the moving display was changed from -3 degrees to +3 degrees. The gain of OKN was found to be inversely proportional to binocular disparity. Evidence for cells in the visual cortex, MT and MST that are sensitive both to visual motion and binocular disparity is reviewed. It is argued that the activity of cells responsive to direction of motion and zero disparity selectively augments OKN and that this enables humans to stabilize the images of parts of the scene in the plane of regard while ignoring competing motion signals arising from other distances.
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PMID:Human optokinetic nystagmus is linked to the stereoscopic system. 259 40

The optokinetic nystagmus is a phylogenetically old reflexive reaction of the eyes to the movements of the visual surroundings. Two components can be distinguished: (1) the direct one is considered to represent a cortically transmitted loop through the posterior parietal areas: MT and MST; (2) the indirect component passes through brain stem nuclei. One of them is the pretectal nucleus of the optic tract in which we found neurons related to the velocity of the moving pattern. Since in neurons of the oculomotor nuclei the neuronal activity is related to eye position, integration must take place somewhere in the circuit. The brain stern-mediated indirect component is influenced by the vestibular organs, not only by semicircular canals but also by otoliths.
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PMID:[Neurophysiologic basis of optokinetic reflex: present state of knowledge]. 921 4

The mechanism of vertigo is unclear. Generally, the peak time or the latency of blood oxygenation level dependent (BOLD) effect is about 6s. However, clinically, the latency of vertigo or nystagmus induced by caloric stimulations is much longer than 6s, commonly about 30s induced by water of 30 degrees C or 44 degrees C. We hypothesize that there is an inhibitive power or mechanism for the occurrence of vestibular vertigo, since it is an unpleasant feeling. The caloric test was performed in healthy volunteers during the BOLD fMRI scanning. The overlaid results of statistical parametric mapping (SPM) showed that three brain regions showed neural activation during vestibular dizziness while deactivation occurred in response to cold water simulation: (1) supplementary motor area (SMA); (2) middle temporal area/medial superior temporal area (MT/MST); (3) visual association area (BA19). The time course of the regions further demonstrated that the signal decreased during the cold-water stimulation and increased during the period of vertigo. We therefore further hypothesize that there may be two forces for the production of vertigo: inhibitory power (IP) and promotive power (PP). The delayed onset of vertigo was the result of the interaction between IP and PP. All of our findings, for the first time, suggested such an original mechanism of vertigo.
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PMID:Why cold water delays the onset of vestibular vertigo--an functional MRI study. 1791 69