In preliminary studies, we attempted to isolate motion mechanisms by measuring threshold contours for motion (direction identification) in L,M cone contrast coordinates. We discovered,in addition to the anticipated luminance motion mechanism (LUM), a spectrally-opponent motion mechanism (SPO). SPO responds to the difference of L and M yet appears distinct from the opponent L,M mechanism which signals hue (red-green, RG). We will thoroughly measure the properties of LUM, SPO and RG, especially quantifying differences between SPO and RG through their detection contours, the relative phases of their L,M,S cone inputs, and their motion adaptation properties. Initial studies suggest that LUM and SPO each extract an opponent-motion signal (e.g. response to difference of right and left moving components), and the net signals from the two motion mechanisms then combine linearly and independently of phase (indicating early motion analysis by separate mechanisms). We will study in detail this early-motion process and subsequent linear combination, and will examine whether motion adaptation and masking transfer across the LUM and SPO mechanisms. We also intend to continue the difficult task of isolating psychophysically the two postreceptoral hue mechanisms red-green (RG) and blue-yellow (BY) in order to quantify their properties: (1) The interaction of the three cone types (L,M,S) at threshold; (2) The effect of temporal frequency on the relative phase of the cone inputs; (3) Any ability to signal motion. Psychophysical isolation is difficult and we have developed procedures which take advantage of disparate cone phase shifts between mechanisms. Threshold contours will be reported in cone contrast coordinates to assess the relative cone weights on a physiologically plausible scale. We hope to resolve two controversial issues: what are the L,M weights for the yellow component of BY; what is the strength of the S input to RG. A significant S input to RG could permit RG and BY alone to explain discrimination of just-perceptible stimuli in the equiluminant plane (without 'higher-order' mechanisms).

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY001808-17
Application #
3256228
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1976-06-30
Project End
1996-06-30
Budget Start
1993-07-01
Budget End
1994-06-30
Support Year
17
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Harvard University
Department
Type
Schools of Arts and Sciences
DUNS #
071723621
City
Cambridge
State
MA
Country
United States
Zip Code
02138
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

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