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At least 397 records · Page 22Linked to original sources
PubMed1982

Plasticity in the oculomotor system.

The oculomotor system, responsible for the control of eye movement, is capable of a number of kinds of plasticity. The demonstration of such plasticity has been aided by several factors, including the present delineation of the system's major subsystems and their purposes; the relatively simple relationships between the system and the mechanical apparatus on which it acts, the eyeball and its muscles; and the development of techniques for studying central nervous system (CNS) activity in awake, behaving animals. Plasticity has been demonstrated by using noninvasive techniques to disturb the normal relationship between vision and eye movements, thereby creating a need for adjustment by the oculomotor system. Current studies are concerned with the location and identity of the responsible modifiable synapses. The cerebellum and the olivocerebellar pathways are definitely involved in several forms of oculomotor plasticity. However, it remains to be determined whether the responsible changes reside within these structures or are located elsewhere in the CNS.

Accommodation, Ocular↗
PubMed1995

Effect of target proximity on transient myopia induced by equidioptric stimuli.

Transient myopia may be exhibited after sustained focus on a near target. This appears to be related to the within-task accommodative response. Although proximally induced accommodation has been shown to produce considerable transient myopia under open-loop conditions, its effect under naturalistic closed-loop conditions remains unclear. Accordingly, the present study examined the effect of target distance on transient myopia for equidioptric stimuli (5 D). A Canon R-1 autorefractor was used to assess the pre- and post-task refractive state objectively. Two tasks were performed monocularly and consisted of either accommodating on a near target at 20 cm (5 D) or a far target at 6 m viewed through a -5 D lens. The former task involved both blur and proximally induced accommodation, whereas the latter consisted of a blur stimulus only. Similar amounts of transient myopia were found under both conditions. These equivalent responses may be related to the relatively small output of proximally induced accommodation believed to be present under closed-loop conditions.

Accommodation, Ocular↗
PubMed1996

[Spontaneous and visually-induced oculomotor reactions in microgravity (Results of Austrian-Russian Experiment "Optovert" performed within the frame of program "Austromir", part II)].

Results of investigation of spontaneous and induced by vertical linear and sinusoid optokinetic stimulation oculomotor reactions in short- and long-term space missions are reported. Adaptation to microgravity was shown to be associated with rearrangement in sensory interactions even on a background of good subjective well-being and absence of abnormal autonomous nervous reactions. In the early period of adaptation to microgravity records were made of modified spontaneous oculomotor activity (spontaneous vertical nystagmus) and vertical optokinetic nystagmus (VOKN) including alterations in amplitude and VOKN amplification coefficient.

Adaptation, Ocular↗
PubMedDate not supplied

[Adaptation in a detector system and differential sensitivity].

It is shown, that if during adaptation the sensitivity of single detectors of the models (1) is constantly decreasing proportionally to the level of their excitation, then the differential sensitivity of the whole system to the stimulus near the adapting stimulus increase. The condition is deduced under which the perceived value of stimulus parameter is invarable during adaptation. Calculated from these conditions invariable values of line inclination, hue of the patch, are in agreement with experimentally obtained data.

Adaptation, Ocular↗
PubMed1951

The effect of varying the intensity and the duration of preexposure upon foveal dark adaptation in the human eye.

The course of foveal dark adaptation was studied as a function of the intensity and duration of preexposure. Four intensities (11,300, 5,650, 1,130, and 565 mL.) and four durations (300, 150, 30, and 15 seconds) were used in all combinations of intensity and duration. The threshold-measuring instrument was a monocular Hecht-Shlaer adaptometer and the threshold measurements were recorded in log micromicrolamberts. There were two subjects and each went through the complete series of intensities and durations five times. The five logarithmic values obtained for each threshold were converted into a geometric mean and these means were the data used in the analysis of the results. The chief results were as follows:- 1. For each subject the final steady threshold value was in the region of 7.0 log micromicroL. 2. As the intensity, or duration, or both, were increased the initial foveal dark adaptation threshold rose, the slope of the curve decreased, and the time to reach a final steady threshold value increased. 3. For those values of preexposure intensity and time for which the product, I x t, is a constant it was found that for the two higher intensities and two longer durations and also for the two lower intensities and two shorter durations, the dark adaptation curves were the same. For other values of I x t = C the curves were generally not the same.

Adaptation, Ocular↗