Related Experiment Video
Updated: Aug 13, 2026

Recording Light-evoked Postsynaptic Responses in Neurons in Dark-adapted, Mouse Retinal Slice Preparations Using Patch Clamp Techniques
Published on: February 11, 2015
Absence of linear subthreshold summation between red-green and luminance mechanisms over a wide range of
K T Mullen1, S J Cropper, M A Losada
1McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Canada. kmullen@violet.vision.mcgill.ca
Abstract:
We have tested the independence of red-green chromatic and luminance mechanisms at detection threshold using a method of subthreshold summation. Stimuli were isoluminant red-green gratings and yellow-black luminance gratings that uniquely activate the red-green color and luminance mechanisms, respectively. Stimuli were Gaussian enveloped 0.25, 1 or 4 cpd sinewave gratings, counter-phase flickered at 0, 5 or 9 Hz. The threshold detection of red-green color contrast was measured in the presence of a subthreshold amount of luminance contrast, and vice versa. The results allow a model of linear summation between the color and luminance mechanisms to be rejected, but are well fitted by a model, assuming that these mechanisms are independent but combine to determine detection by probability summation, with a high summation index (median value = 4). We conclude that there are independent red-green chromatic mechanism and luminance detection mechanisms over this range of spatio-temporal conditions.
Related Concept Videos
The Retina
Graded Potential
Graded potentials fall into two categories: depolarizing and hyperpolarizing. Depolarizing graded potentials typically occur when sodium (Na+) or calcium...
Anatomy of the Eyeball
Photoreceptors and Visual Pathways
Color Vision

