This is a proposal to continue measuring and modeling human psychophysical data that deal with spatial vision and its dependence on the temporal and chromatic parameters of the stimulus. We normally control the effects of eye movements on these interactions by stabilizing the retinal image and providing any desired motion or other temporal variations at the distal stimulus. This method of fixation control will be used in all the proposed studies. By a similar technique, we have simulated realistic scotoma conditions in normal subjects, which would be of value in studying the effects of pathologies that are located in the visual field. Topics we propose to study include: (1) Effects of both local and global adaptation processes on the thresholds for stabilized images, particularly isoluminance chromatic gratings. (2) Threshold and suprathreshold effects of retinal inhomogeneity on spatial vision, using large-area, quasi-sinusoidal targets. Previous experimental and theoretical results will be extended to include effects of target shape, temporal frequency and ultimately, chromatic gratings. By measuring contrast thresholds for circular targets whose spatial frequency varies with eccentricity, we will obtain spatiotemporal threshold surfaces, both luminous and chromatic, that are corrected for spatial inhomogeneity effects over a large retinal area. Cortically homogeneous stimuli produced in this way will also be used to study cortical mechanisms of spatial vision, with standard experimental techniques. (3) Suprathreshold contrast response surfaces, both luminous and chromatic, measured by a contrast-matching technique, will be compared with the results predicted from the threshold surfaces by a very general, nonlinear model. These comparisons will be used to isolate nonlinear mechanisms that are confined to local regions of the spatiotemporal frequency domain.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY001128-15
Application #
3255698
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1975-05-01
Project End
1991-04-30
Budget Start
1989-05-01
Budget End
1990-04-30
Support Year
15
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Sri International
Department
Type
DUNS #
City
Menlo Park
State
CA
Country
United States
Zip Code
94025
Levi, D M; Polat, U (1996) Neural plasticity in adults with amblyopia. Proc Natl Acad Sci U S A 93:6830-4
Kelly, D H; Martinez-Uriegas, E (1993) Measurements of chromatic and achromatic afterimages. J Opt Soc Am A 10:29-37
Kelly, D H (1990) Moving gratings and microsaccades. J Opt Soc Am A 7:2237-44
Kelly, D H (1989) Opponent-color receptive-field profiles determined from large-area psychophysical measurements. J Opt Soc Am A 6:1784-93
Kelly, D H; Burbeck, C A (1987) Further evidence for a broadband, isotropic mechanism sensitive to high-velocity stimuli. Vision Res 27:1527-37
Kelly, D H (1985) Retinal inhomogeneity. III. Circular-retina theory. J Opt Soc Am A 2:810-9
Kelly, D H (1985) Receptive-field-like functions inferred from large-area psychophysical measurements. Vision Res 25:1895-900
Kelly, D H (1985) Visual processing of moving stimuli. J Opt Soc Am A 2:216-25