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PubMed1951

[Glare].

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Adaptation, Ocular↗
PubMed1963

Scotopic spectral sensitivity in the monkey.

Three rhesus monkeys learned to adjust a small illuminated spot to threshold intensity. Then, while dark adapted, they "tracked" their thresholds to stimuli spaced across the visible wavelength spectrum. Spectral sensitivity functions were determined for each animal from these threshold records. The functions agreed well with results obtained from a human subject in the same apparatus, and with the standard human scotopic function defined by the International Commission on Illumination. However, the monkeys' relative sensitivity was slightly higher in the long-wavelength portion of the spectrum.

Acclimatization↗
PubMed1998

Effects of lesions of the oculomotor vermis on eye movements in primate: saccades.

We studied the effects on saccades of ablation of the dorsal cerebellar vermis (lesions centered on lobules VI and VII) in three monkeys in which the deep cerebellar nuclei were spared. One animal, with a symmetrical lesion, showed bilateral hypometric horizontal saccades. Two animals, with asymmetrical lesions, showed hypometric ipsilateral saccades, and saccades to vertically positioned targets were misdirected, usually deviating away from the side to which horizontal saccades were hypometric. Postlesion, all animals showed an increase (2- to 5-fold) in trial-to-trial variability of saccade amplitude. They also showed a change in the ratio of the amplitudes of centripetal to centrifugal saccades (orbital-position effect); usually centrifugal saccades became smaller. In the two animals with asymmetrical lesions, for saccades in the hypometric direction, latencies were markedly increased (up to approximately 500 ms). There was also an absence of express and anticipatory saccades in the hypometric direction. When overall saccade latency was increased, centrifugal saccades became relatively more delayed than centripetal saccades. The dynamic characteristics of saccades were affected to some extent in all monkeys with changes in peak velocity, eye acceleration, and especially eye deceleration. There was relatively little effect of orbital position on saccade dynamics, however, with the exception of one animal that showed an orbital position effect for eye acceleration. In a double-step adaptation paradigm, animals showed an impaired ability to adaptively adjust saccade amplitude, though increased amplitude variability postlesion may have played a role in this deficit. During a single training session, however, the latency to corrective saccades-which had been increased postlesion-gradually decreased and so enabled the animal to reach the final position of the target more quickly. Overall, both in the early postlesion period and during recovery, changes in saccade amplitude and latency tended to vary together but not with changes in saccade dynamics or adaptive capability, both of which behaved relatively independently. These findings suggest that the cerebellum can adjust saccade amplitude and saccade dynamics independently. Our results implicate the cerebellar vermis directly in every aspect of the on-line control of saccades: initiation (latency), accuracy (amplitude and direction), and dynamics (velocity and acceleration) and also in the acquisition of adaptive ocular motor behavior.

Adaptation, Physiological↗
PubMed2004

Gravity-dependent and gravity-independent gain changes during vertical vestibulo-ocular reflex (VOR) adaptation.

The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased or decreased with monkeys in a side down position, and the gains were tested with the axis of rotation tilted in 10 degrees increments from left- to right-side-down. Gain changes, expressed as a percentage of the preadapted values, were plotted as a function of head tilt, and fit with a cosine function. The amplitude of the cosine was half of the gravity-dependent component of the gain change and the bias, the gravity independent component. The largest changes in the gain of both components occurred in the first 30 min and continued at a slower rate throughout adaptation. The gravity-dependent and -independent gain changes were larger for gain decreases than for gain increases, but both components had similar dynamics. We conclude that the alteration in gain of the aVOR always occurs in the context of gravity.

Adaptation, Physiological↗
PubMed1998

Learning in the oculomotor system: from molecules to behavior.

A combination of system-level and cellular-molecular approaches is moving studies of oculomotor learning rapidly toward the goal of linking synaptic plasticity at specific sites in oculomotor circuits with changes in the signal-processing functions of those circuits, and, ultimately, with changes in eye movement behavior. Recent studies of saccadic adaptation illustrate how careful behavioral analysis can provide constraints on the neural loci of plasticity. Studies of vestibulo-ocular adaptation are beginning to examine the molecular pathways contributing to this form of cerebellum-dependent learning.

Animals↗