title: Spectral sensitivity as revealed by isolated step onsets and step offsets.
abstract: Opponent-colour spectral sensitivity functions are traditionally elicited with increments; the temporal presentation of these increments is usually step onset and step offset. However, there are both physiological and psychophysical data suggesting differences in sensitivity for spectral step onsets and step offsets. The purpose of this study was to elicit opponent-colour spectral sensitivity functions with isolated step onsets and offsets, and to compare the form and sensitivity of these functions. Spectral sensitivity functions were determined for large, long duration, step onset and step offset stimuli. Four human observers participated in the study. The opponent-colour functions obtained for onsets and offsets are largely similar in both form and sensitivity. Of particular interest is the finding that there is no reduction in sensitivity for blue offsets. These data are consistent with recently published psychological data and apparently at variance with physiological data that suggest a paucity of S-cone OFF-neurones in the primate retina and dorsal lateral geniculate nucleus (dLGN).
authors.affiliation: Department of Biomedical Sciences, Southern College of Optometry, Memphis, TN 38104, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D003118:Color Perception; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time; D014785:Vision, Ocular / Q000502:physiology*