Related Experiment Video
Updated: Aug 19, 2026

Visualizing Visual Adaptation
Published on: April 24, 2017
Energy model for contrast detection: spatial-frequency and orientation selectivity in grating summation
1Department of Vision Sciences, Glasgow Caledonian University, City Campus, Cowcaddens Road, Glasgow, G4 0BA, Scotland, UK. vma@gcal.ac.uk
Abstract:
Models of spatial vision usually assume a "front-end" of spatial-frequency and orientation selective channels. Subthreshold-summation studies have provided some of the strongest support for this notion. We applied a single-channel energy model and a multiple-channels probability-summation model to explore subthreshold-summation phenomena. We measured the contrast thresholds for detection of two superimposed Gabor patches as a function of the spatial-frequency and orientation difference between the components. The stimuli were centred 7.5 deg above the fixation point and were windowed by a Gaussian function with one of two different spatial spreads. We have shown that the spatial-frequency and orientation selectivity in subthreshold summation of Gabor patches is determined by the similarity (cross-correlation) between the stimulus components. A single-channel energy model as well as a multiple-channels probability-summation model could explain the summation data.
Related Concept Videos
The Retina
Vision
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
Color Vision

