The first main objective of this study is to isolate psychophysically three post-receptoral mechanisms in human vision, luminance (Lum), red- green chromatic (RG), blue-yellow chromatic (BY), and to study some important properties of the mechanisms: 1) The interactions of the three cone types (L, M and S) in each mechanism at threshold. 2) The effect of temporal frequency on the relative phase of the cone interactions. 3) The ability of each mechanism to signal motion. Psychophysical isolation can be extremely difficult to achieve and we have developed new procedures which we believe will work--procedures which take advantage of different cone phase lags within the three mechanisms. There are some controversial questions which we then hope to answer. One is the ratio of L and M inputs in the yellow limb of the BY mechanism. Another has to do with the way in which S cones signal motion (an effect which we have clearly demonstrated); is this via the weak S cone input to the Lum mechanism? This leads to an even more basic question: are BY or RG capable of signalling motion? The putative motion sensitivity of the RG system is extremely controversial and very little threshold data (data most likely to be free of artifact) are available. We are especially interested in quantifying S cone inputs to the three mechanisms. The S cones are disproportionally vulnerable in many occular conditions (e.g. retinitis pigmentosa, macular degeneration), as well as several systemic disorders (e.g. diabetes mellitus), and so a better basic understanding of the S cone contribution to luminance and color may have future clinical applications as well. The second main objective is to understand better the facilitation by suprathreshold luminance edges of chromatic detection across the luminance boundary. A simple hypothesis for the facilitation is that it is the consequence of a reduction in spatio-temporal uncertainty. We have designed two experiments, using detection statistics, to test this hypothesis. Our previous data show that the luminance edge linearizes chromatic detection across time; additional experiments will test whether this linearity also occurs across space, so that the observer is sensitive to the linear chromatic difference across the luminance edge (like a linear, chromatic double-opponent mechanism).

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
Project #
Application #
Study Section
Visual Sciences B Study Section (VISB)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Harvard University
Schools of Arts and Sciences
United States
Zip Code
Stromeyer 3rd, C F; Martini, P (2003) Human temporal impulse response speeds up with increased stimulus contrast. Vision Res 43:285-98
Stromeyer 3rd, C F (2003) Temporal asymmetry in motion masking: a shortening of the temporal impulse response function. Vision Res 43:261-8
Stromeyer 3rd, C F; Gowdy, P D; Chaparro, A et al. (2000) Colour adaptation modifies the temporal properties of the long- and middle-wave cone signals in the human luminance mechanism. J Physiol 526 Pt 1:177-94
Stromeyer 3rd, C F; Thabet, R; Chaparro, A et al. (1999) Spatial masking does not reveal mechanisms selective to combined luminance and red-green color. Vision Res 39:2099-112
Zemany, L; Stromeyer 3rd, C F; Chaparro, A et al. (1998) Motion detection on flashed, stationary pedestal gratings: evidence for an opponent-motion mechanism. Vision Res 38:795-812
Stromeyer 3rd, C F; Chaparro, A; Rodriguez, C et al. (1998) Short-wave cone signal in the red-green detection mechanism. Vision Res 38:813-26
Stromeyer 3rd, C F; Chaparro, A; Tolias, A S et al. (1997) Colour adaptation modifies the long-wave versus middle-wave cone weights and temporal phases in human luminance (but not red-green) mechanism. J Physiol 499 ( Pt 1):227-54
Chaparro, A; Stromeyer 3rd, C F; Chen, G et al. (1995) Human cones appear to adapt at low light levels: measurements on the red-green detection mechanism. Vision Res 35:3103-18
Picotte, C J; Stromeyer 3rd, C F; Eskew Jr, R T (1994) The foveal color-match-area effect. Vision Res 34:1605-8
Chaparro, A; Stromeyer 3rd, C F; Kronauer, R E et al. (1994) Separable red-green and luminance detectors for small flashes. Vision Res 34:751-62

Showing the most recent 10 out of 19 publications