Stephen Lehmkuhle | University of Minnesota, Rochester (original) (raw)

Papers by Stephen Lehmkuhle

Investigative ophthalmology, 1976

A grating pattern presented to one eye of an individual capable of alternating suppression induce... more 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.

Investigative ophthalmology & visual science, 1990

The effects of long-term monocular lid-suture deprivation on visual-evoked cortical potentials (V... more The effects of long-term monocular lid-suture deprivation on visual-evoked cortical potentials (VEPs) and flash- and pattern-evoked electroretinograms (FERGs and PERGs, respectively) were assessed in the cat. VEPs were virtually eliminated when recorded with the deprived eye, indicating that the lid suture produced a severe amblyopia in that eye. In contrast, FERGs and PERGs were more similar for both deprived and nondeprived eyes and comparable to those recorded in normal animals. The current findings demonstrate that long-term deprivation (3-4 yr) does not produce systematic changes in the electroretinogram.

Choice Reviews Online, 2003

... Disabilities: Assessment and Implications 35 Stephen Oross III and Charles B. Woods 3. Enhanc... more ... Disabilities: Assessment and Implications 35 Stephen Oross III and Charles B. Woods 3. Enhancing Performances of Individuals with Mental Retardation: Manipulations of Visual Structure 81 Michael T. Carlin, Sal Soraci Jr., and Christina Strawbridge 4. Stimulus Overselectivity ...

Journal of the American Optometric Association, 1990

Visual information travels from the retina to visual cortical areas along at least two parallel p... more Visual information travels from the retina to visual cortical areas along at least two parallel pathways. In this paper, anatomical and physiological evidence is presented to demonstrate the existence of, and trace these two pathways throughout the visual systems of the cat, primate, and human. Physiological and behavioral experiments are discussed which establish that these two pathways are differentially sensitive to stimuli that vary in spatial and temporal frequency. One pathway (M-pathway) is more sensitive to coarse visual form that is modulated or moving at fast rates, whereas the other pathway (P-pathway) is more sensitive to spatial detail that is stationary or moving at slow rates. This difference between the M- and P-pathways is related to some spatial and temporal effects observed in humans. Furthermore, evidence is presented that certain diseases selectively comprise the functioning of M- or P-pathways (i.e., glaucoma, Alzheimer's disease, and anisometropic amblyopi...

PubMed, Aug 1, 1976

Attention Perception & Psychophysics, 1976

Choice Reviews Online, Dec 1, 2003

PubMed, Feb 1, 1990

Science, Apr 16, 1976

Grating acuity, the ability to resolve high-contrast square-wave gratings, was measured in a falc... more 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.

Vision Research, 1983

Contrast thresholds for sinewave gratings were measured as a function nf the number of cycles in ... more Contrast thresholds for sinewave gratings were measured as a function nf the number of cycles in the grating for two different orientations and three spatial frequencies. At high spatial frequencies, where an oblique effect of contrast sensitivity was demonstrated. there was a greater increase in ~~~~~~s~ sensitivity as a function of the number of cycles for the vertical gratings than for oblique gratings. At a lower spatial frequency, where the contrast sensitivity ~~niso~ropy was greatly diminish~d~ both orientations displayed a similar increase in contrast sensitivity when the number of cycles in the grating was increased.

Journal of Neurophysiology, Nov 1, 1984

Extracellular responses of Y-cells in the A-laminae and in lamina C of the cat dorsal lateral gen... more Extracellular responses of Y-cells in the A-laminae and in lamina C of the cat dorsal lateral geniculate nucleus were recorded and compared for several sine-wave grating presentations. Both spatial and temporal contrast sensitivity functions were determined for these cells as well as suprathreshold response functions at 0.2 and 0.4 contrast. Qualitatively, the responses of the lamina C Y-cells were very similar to Y-cells of the A-laminae; differences were of a quantitative nature. At threshold, lamina C Y-cells were more sensitive at all spatial and temporal frequencies tested. Suprathreshold results showed no major differences in fundamental response amplitude between laminar Y-cells. Interlaminar differences were found with respect to second harmonic response amplitude. Lamina C Y-cells gave the largest overall second harmonic response for all stimulus conditions. A trend was observed for these laminar Y-cells such that the second harmonic responses were highest for Y-cells of lamina C, intermediate for lamina A Y-cells, and lowest for those of lamina A1. Based on differences in projection pattern and present electrophysiological results, we conclude that the lamina C Y-cells may represent a population of cells that is distinct from A-laminae Y-cells. These lamina C Y-cells provide a significant input to visual cortex.

Springer eBooks, 1997

We report physiological and psychophysical studies that further expand and delineate two of the t... more We report physiological and psychophysical studies that further expand and delineate two of the tests of Enoch’s Layer-by-Layer Perimetry. In the physiological studies we show that single ganglion cells give responses comparable to human responses. In the human studies we demonstrate that a corresponding sensitization response exists in the OFF-channel, that a “pure” flicker mechanism smaller than the transient-like mechanism exists, and that an orientation bias exists in the cortical properties mapped with a variation of these tests. These results offer extensions of layer-by-layer perimetry for the clinical testing of additional layers of the visual system.

Journal of the Optical Society of America, 1982

Optometry and Vision Science, Dec 1, 1994

Vision Research, 1986

The sensitivity of X- and Y-cells in the dorsal lateral geniculate nucleus of the cat to small, t... more The sensitivity of X- and Y-cells in the dorsal lateral geniculate nucleus of the cat to small, temporally modulated displacements of grating stimuli was measured at 0.175, 0.25, 0.50, 1.00, and 2.00 c/deg. For every cell, two threshold measures were determined: first, a contrast threshold with a counterphase grating and then a displacement threshold with a grating matched in spatial frequency, but whose contrast was 2.5 times the threshold value. The results showed that displacement thresholds of both X- and Y-cells decreased with increasing spatial frequency. At low spatial frequencies, mean displacement thresholds of X- and Y-cells were similar, but at intermediate spatial frequencies, Y-cell thresholds were lower than X. X-cell displacement thresholds were lower than Y only at the highest spatial frequency tested. Consistent with previous reports, contrast thresholds also varied with spatial frequency for both X- and Y-cells. The local luminance differences produced by the contrast threshold and displacement threshold stimuli for the two classes of cells were compared. Across all spatial frequencies, the change in position of the gratings at displacement threshold produced smaller luminance differences than the counterphase gratings at contrast threshold. This enhanced sensitivity of X- and Y-cells to a local luminance changes produced by grating displacement was related to the high spatial contrast of the grating and not to the displacement per se.

Science, Jul 1, 1977

Stereoscopic depth perception is demonstrated in the falcon, a non-mammalian with binocular visio... more 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.