Motion contrast: A new metric for direction discrimination

Citations of this article
Mendeley users who have this article in their library.


The Adelson-Bergen energy model (Adelson, E. H., and Bergen, J. R. (1985). Spatiotemporal energy models for the perception of motion. Journal of the Optical Society of America A, 2, 284-299) is a standard framework for understanding first-order motion processing. The opponent energy for a given input is calculated by subtracting one directional energy measure (E(L)) from its opposite (E(R)), and its sign indicates the direction of motion of the input. Our observers viewed a dynamic sequence of gratings (1 c/deg) equivalent to the sum of two gratings moving in opposite directions with different contrasts. The ratio of contrasts was varied across trials. We found that opponent energy was a very poor predictor of direction discrimination performance. Heeger (1992). Normalization of cell responses in cat striate cortex. Visual Neuroscience, 9, 181-197) has suggested that divisive inhibition amongst striate cells requires a contrast gain control in the energy model. A new metric can be formulated in the spirit of Heeger's model by normalising the opponent energy (E(L)-E(R)) with flicker energy, the sum of the directional motion energies (E(L)+E(R)). This new measure, motion contrast (E(L)-E(R))/(E(L)+E(R)), was found to be a good predictor of direction discrimination performance over a wide range of contrast levels, but opponent energy was not. Discrimination thresholds expressed as motion contrast were around 0.5±0.1 for the sampled drifting gratings used in our experiments. We show that the dependence on motion contrast, and the threshold of about 0.5, can be predicted by a modified opponent energy model based on current knowledge of the response functions and response variance of cortical cells. Copyright (C) 1999 Elsevier Science Ltd.




Georgeson, M. A., & Scott-Samuel, N. E. (1999). Motion contrast: A new metric for direction discrimination. Vision Research, 39(26), 4393–4402.

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free