Changes in Ricco's area with background luminance in the S-cone pathway.

Purpose: The area of complete spatial summation (Ricco's area) for achromatic stimuli has previously been shown to decrease with increased background luminance. A popular hypothesis is that such a phenomenon reflects increased center-surround antagonism within the receptive field of the retinal ganglion cell. We wished to investigate if similar changes in Ricco's area occur with blue background luminance for the S-cone pathway, guided by the knowledge that the retinal ganglion cells with S-cone input do not display S-cone-mediated center-surround antagonism (S+/S-).

On the search for an appropriate metric for reaction time to suprathreshold increments and decrements.

Weber contrast, DeltaL/L, is a widely used contrast metric for aperiodic stimuli. Zele, Cao & Pokorny [Zele, A. J.

Resolution acuity for equiluminant gratings of S-cone positive or negative contrast in human vision.

We measured resolution acuity separately for gratings with positive (+S) and negative (-S) S-cone contrast at different eccentricities in the temporal retina to determine if the resolution performance is limited by a single bipolar opponent mechanism. Gratings were modulated from an achromatic background in either the 90 or 270 deg direction in DKL space. Two additional directions were tested to examine the effects of increased lens yellowing and macular pigment absence in the periphery.

Sensitivity to stimulus onset and offset in the S-cone pathway.

Previous work [Vassilev, capital A, Cyrillic., Mihaylova, M., Racheva, K.

Human S-cone vision: relationship between perceptive field and ganglion cell dendritic field.

We measured the S-cone contrast threshold for stimuli of different size modulated along the white -90 deg direction in the isoluminant plane of DKL color space. The stimuli were presented at eccentricities of 5-30 deg in the horizontal temporal retinal meridian. Ricco's area of complete spatial summation was estimated using a bilinear fit of the log threshold/log area function.

Spatial summation of S-cone ON and OFF signals: effects of retinal eccentricity.

We studied spatial summation for S-cone ON and OFF signals as a function of retinal eccentricity in human subjects. S-cone isolation was obtained by the two-colour threshold method of Stiles, modified by adding blue light to the yellow background. Test stimuli were blue light increments or decrements within a circular area of variable size.

On the delay in processing high spatial frequency visual information: reaction time and VEP latency study of the effect of local intensity of stimulation.

Saleh and Bonnet [Fechner Day 98, p. 344] have shown that, upon parafoveal stimulation and up to 6.5 c/deg, reaction time (RT) is a function of grating contrast multiplied by grating period.