|AFFILIATIONS||Professor of Chemistry, University of California, Santa Cruz|
|RESEARCH||My laboratory is involved in a variety of psychophysical studies aimed at furthering our understanding of spatial perception. Using detection, matching, adaptation, and masking paradigms, we investigate spatial visual processing at threshold and suprathreshold levels. Spatial frequency, orientation, motion, contrast, accommodative- stimuli, and statistical spatial correlations are among the properties investigated. We have been particularly interested in comparing the performance of the human visual system in analyzing spatial information defined by luminance variations and by chromatic variations and in the ability to detect spatio-temporal correlations among stimuli having differing spatio-chromatic properties. Professors Karen DeValois and Russell DeValois have been collaborators in many of these studies.Spatial information in the natural visual environment. We are interested in the nature of spatio-chromatic information in the ‘normal’ visual environment and its relationship to mechanisms of visual processing. We have collected a variety of scenes representative of normal visual input and are analyzing their spatial and spatio-chromatic content. Our goals are to understand the requirements of the visual system in terms of the input which must be processed, to assess the relevance of ‘laboratory’ psychophysical data to normal visual processing, and to compare known mechanisms of perceptual processing in regard to their efficiency in processing information encountered in the normal visual world.
Human electrophysiology and clinical applications. We have measured and characterized visual evoked potentials (VEPs) for isoluminant stimuli and have utilized these VEPs to study spatio-chromatic visual processing in observers with normal and anomalous color vision. These studies utilize patterns which vary along selected directions of a cone activation color space and are chosen to modulate specific cone, opponent, or luminance mechanisms. Aug-menting the VEP by pattern electroretinograms for isoluminant stimuli, we will compare transformation of chromatic information at retinal and cortical levels. We are also applying the spatio-chromatic VEP to clinical studies of observers with congenital and acquired (central serous and diabetes) anomalous color vision. Professor Anthony Adams has been a collaborator in many of these studies.
Switkes E, Bradley A and Schor C: Readily Visible Changes in Color Contrast Are Insufficient to Stimulate Accommodation. (1990) Vision Res. 30: 1367-1376.
Kooi FL, DeValois RL and Switkes E: Spatial Localization Across Channels. (1991) Vision Res. 31:1627-1631.
Rabin J, Adams AJ and Switkes E: Perceptual Ambiguity and the Short Wavelength Visual Pathway. (1992) Vision Res. 32: 399-401.
Kooi FL, DeValois KK, Switkes E, and Grossof D: Higher Order Factors Influencing the Perception of Sliding and Coherence of a Plaid. (1992) Perception. 21: 583-598.
Crognale MA, Switkes E, Schneck ME, HÊgerstrˆm-Portnoy G, Adams A: Application of the spatiochromatic visual evoked potential to detection of congenital and acquired color-vision deficiencies. (1993) J. Op. Soc. Am. A, 10: 1818-1825.
Schneck, M.E., Fortune, B., Switkes, E., Crognale, M. & Adams, A.J. Acute Effects of Blood Glucose on Chromatic Visually Evoked Potentials in Persons with Diabetes and in Normal Persons. (1997) Invest. Ophthalmol. and Vis. Science 38, 800-810.
De Valois, R.L., De Valois, K.K., Switkes, E. and Mahon, L. Hue Scaling of Isoluminant and Cone-specific Lights. (1997) Vision Research 37, 885-897.
Switkes, E & Crognale, M. A. Comparison of Color and Luminance Contrast: Apples vs. Oranges? (1999) Vision Research, 39, 1823-18.