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Stimulus-specific Cortical Visual Evoked Potential Morphological Patterns
Published on: May 12, 2019
Chromatic temporal integration and retinal eccentricity: psychophysics, neurometric analysis and cortical pooling
William H Swanson1, Fei Pan, Barry B Lee
1Indiana University, School of Optometry, 800 East Atwater Avenue, Bloomington, IN 47405-3680, USA. wilswans@indiana.edu
Vision Research
|April 18, 2008
Summary
Peripheral vision has reduced color sensitivity, especially for red-green (L-M) and blue-yellow (S) pathways. Temporal integration in the periphery shortens, partly explaining sensitivity loss, with some L-M loss originating in the cortex.
Area of Science:
- Visual Neuroscience
- Ophthalmology
- Human Physiology
Background:
- Chromatic sensitivity declines in the peripheral retina, impacting color perception.
- This decline is more pronounced for long- (L) to middle-wavelength (M) cone opponent pathways compared to short-wavelength (S) pathways.
- Temporal integration, the duration over which visual stimuli are processed, may differ between central and peripheral vision.
Purpose of the Study:
- To investigate how chromatic temporal integration (critical duration) changes with eccentricity in the human visual system.
- To determine if altered temporal integration in the periphery accounts for reduced chromatic sensitivity.
- To explore the potential cortical contribution to the loss of L-M sensitivity in peripheral vision.
Main Methods:
- Psychophysical estimation of chromatic temporal integration (critical duration) as a function of visual field eccentricity.
- Comparison of psychophysical findings with neurometric contrast sensitivities of retinal ganglion cells.
- Modeling of cortical pooling mechanisms to account for discrepancies between psychophysical and physiological data.
Main Results:
- Critical duration for chromatic temporal integration decreased by approximately 50% from the fovea to 20 degrees eccentricity.
- This reduction in temporal integration partially explains the decreased L-M sensitivity and almost fully explains the decreased S-cone sensitivity in the periphery.
- Neurometric contrast sensitivity in retinal ganglion cells followed Poisson statistics, contrasting with the Bloch's law observed in psychophysical data.
Conclusions:
- Reduced temporal integration in the peripheral retina contributes to diminished chromatic sensitivity.
- A portion of the L-M sensitivity loss in the periphery likely originates from cortical processing.
- Cortical pooling models, including uncertainty about stimulus timing, may reconcile differences between neural and behavioral measures of chromatic sensitivity.
