PT  - JOURNAL ARTICLE
AU  - Heess, Nicolas
AU  - Bair, Wyeth
TI  - Direction Opponency, Not Quadrature, Is Key to the 1/4 Cycle Preference for Apparent Motion in the Motion Energy Model
AID  - 10.1523/JNEUROSCI.1271-10.2010
DP  - 2010 Aug 25
TA  - The Journal of Neuroscience
PG  - 11300--11304
VI  - 30
IP  - 34
4099  - http://www.jneurosci.org/content/30/34/11300.short
4100  - http://www.jneurosci.org/content/30/34/11300.full
SO  - J. Neurosci.2010 Aug 25; 30
AB  - Sensitivity to visual motion is a fundamental property of neurons in the visual cortex and has received wide attention in terms of mathematical models. A key feature of many popular models for cortical motion sensors is the use of pairs of functions that are related by a 90° phase shift. This phase relationship, known as quadrature, is the hallmark of the motion energy model and played an important role in the development of a class of model dubbed elaborated Reichardt detectors. For decades, the literature has supported a link between quadrature and the observation that motion detectors and human observers often prefer a 1/4 cycle displacement of an apparent motion stimulus that consists of a pair of sinusoidal gratings. We show that there is essentially no link between quadrature and this preference. Quadrature is neither necessary nor sufficient for a motion sensor to prefer 1/4 cycle displacement, and motion energy is not maximized for a 1/4 cycle step. Other properties of motion sensors are the key: the opponent subtraction of two oppositely tuned stages that individually have sinusoidal displacement tuning curves. Thus, psychophysical and neurophysiological data revealing a preference at or near 1/4 cycle displacement do not offer specific support for common quadrature or energy-based motion models. Instead, they point to a broader class of model.