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Biomedical subjects

R Held

Publications and source records attributed to R Held.

At least 73 records · Page 4Linked to original sources
PubMed1979

Monkeys show an oblique effect.

Monkeys aligned a cursor bar with high-contrast square-wave gratings presented in a variety of orientations. Alignment time increased with increasing spatial frequency from 6 to 24 cycles deg-1 regardless of the orientation of the grating. At higher spatial frequencies, alignment tasks took longer for obliquely oriented gratings than for horizontal and vertical ones. Reducing grating contrast by blurring the image of the 24 cycle deg-1 grating also produced longer alignment times for the obliques. These data indicate that monkeys have an oblique effect similar to that found in humans, implying that the monkey is a useful animal model for investigating the development of meridional anisotropies.

Animals↗
PubMed1979

Strabismic amblyopia in infants.

Monocular acuities, in two infants with nonaccommodative comitant esotropia, were measured before and during occlusion therapy. The results indicate that strabismic amblyopia is present within the first year of life and that the infant visual system is remarkably sensitive to short periods of monocular occlusion during this time period.

Amblyopia↗
PubMed1979

Development of amblyopia in infants.

New techniques have permitted serial assessments of visual acuity in infants. Acuity measurements in infants with astigmatism did not reveal meridional amblyopia during the first year of life. Measurements in infants with esotropia showed marked differences in acuity of the two eyes as early as the first 6 months of life. Therapeutic occlusion of the non-deviating eye improves the acuity of the deviating eye but at the expense of the occluded eye. After discontinuing occlusion, rapid increases in acuity of the formerly occluded eye can occur.

Aging↗
PubMed1978

Astigmatism in infants.

Compared with children of school age, infants show ten times the incidence and considerably greater amounts of clinically significant astigmatism. The amount begins to decrease in the second semester of life, and the incidence declines during the third year. The unanticipated results bear on both the etiology and the neural sequelae of astigmatism.

Age Factors↗
PubMed1975

Orientational anisotropy in infant vision.

Infants prefer to look at horizontal and vertical gratings rather than at oblique gratings only when they are at or near threshold spatial frequencies, as would be expected if acuity for oblique edges is lower than that for horizontal and vertical edges. That such a bias exists as early as 6 weeks of age suggests that the orientational asymmetry of the visual system depends on endogenous maturation rathat than exposure to a carpentered world.

Age Factors↗
PubMed1975

Comparison of visually guided reaching in normal and deprived infant monkeys.

A stump-tailed macaque, deprived of sight of its hands and body since shortly after birth, appears to be deficient in the accuracy and precision of its visually guided reaching. These deprived monkeys quickly develop adequate reaches if they are allowed to view their hands. To assess the deficit, we developed a method of open-loop testing (no sight of the reaching limb) for use on both an experimental group deprived of sight of limbs and a control group raised under identical restraints but allowed sight of limbs. The results show that the deprived monkeys can learn to reach a given visible target, but the learned reach is not as precise in the training condition or as precise to new target directions as it is for controls. Furthermore, there is little intermanual transfer of reaching skill for the experimentals but nearly 100% transfer for the controls. Finally, experimentals show a loss of precision in retention testing following a lack of practice, but controls do not. We conclude that the differences in visually guided reaching behavior of the two groups is evidence that the normal accuracy results from unconstrained vision of the hands which produces a mapping of the coordinates of motor response onto the space of vision.

Animals↗