Biomedical subjects
Publications and source records attributed to S W Lehmkuhle.
Stereoscopic depth perception is demonstrated in the falcon, a non-mammalian with binocular vision. This result complements recent physiological evidence for binocular interaction in the bird visual system, and suggests that stereopsis may be a general attribute of vertebrate vision and not an exclusive product of mammalian evolution.
Grating acuity, the ability to resolve high-contrast square-wave gratings, was measured in a falcon and in humans under comparable conditions. This behavioral test of falcon acuity supports the common belief that Falconiformès have superb vision-the faclon's threshold was 160 cycles per degree, while the human thresholds were 60 cycles per degree. Falcon acuity, however, was much more dependent on lumanance, declining sharply with decreases in luminance.
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A grating pattern presented to one eye of an individual capable of alternating suppression induces a visual aftereffect (contrast threshold elevation), even when the pattern is phenomenally suppressed from vision. This finding indicates that strabismic suppression occurs within the visual system after the site of the aftereffect, and points out a similarity between strabismic suppression and binocular rivalry suppression.
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