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Spectral sensitivity as revealed by isolated step onsets and step offsets
1Department of Biomedical Sciences, Southern College of Optometry, Memphis, TN 38104, USA.
Summary
Spectral sensitivity functions for opponent colours were similar for step onsets and offsets in human observers. This challenges physiological data suggesting fewer neural pathways for offset stimuli, particularly for blue colours.
Area of Science:
- Vision science
- Neuroscience
- Human psychophysics
Background:
- Opponent-colour spectral sensitivity functions are typically measured using stimulus increments.
- Existing physiological and psychophysical data suggest potential differences in visual sensitivity between stimulus onsets and offsets.
Purpose of the Study:
- To elicit opponent-colour spectral sensitivity functions using isolated step onsets and offsets.
- To compare the form and sensitivity of these functions between onsets and offsets.
Main Methods:
- Determined spectral sensitivity functions for large, long-duration, step onset, and step offset stimuli.
- Utilized four human observers in the study.
Main Results:
- Opponent-colour functions for onsets and offsets showed substantial similarity in both form and sensitivity.
- No reduction in sensitivity was observed for blue colour offsets.
Conclusions:
- The findings support recent psychophysical data regarding visual processing of stimulus onsets and offsets.
- These results appear to contradict physiological data indicating a lack of S-cone OFF-neurones in primate visual pathways.