Neuroscientists find greater complexity in how we perceive motion

December 5, 2011

How we perceive motion is a significantly more complex process than previously thought, researchers at New York University's Center for Neural Science, Stanford University and the University of Washington have found. Their results, which appear in the journal Current Biology, show that the relationship between the brain and visual perception varies, depending on the type of motion we are viewing.

Neuroscientists have posited that our perception of motion is derived from a relatively simple process—that is, it relies on a single cortical area in the brain. This region, MT, has a well-established role in processing information about moving visual objects. However, less clear is the scope of its influence—does it dictate our ability to detect all types of motion or is its function more limited or, perhaps, more nuanced?

With this in mind, the NYU-led team examined how the visual system processes two types of motion: local motion, which involves tracking signals that fall within a small retinal area, and global motion, in which several movements are integrated over larger areas. Specifically, they monitored activity in MT to determine if its neurons were active in response to both types of motion.

In normal scenes, local and global motion are normally in agreement. Here, the researchers conducted experiments in which macaque monkey and human subjects watched specially crafted patterns in which the local and global motion information were in competition. The researchers made physiological and perceptual measurements of brain activity.

Their results showed notable differences in how the visual system functions in processing local and global motion. They found that neuronal activity in MT was controlled by the local motion in the stimulus and unaffected by global motion. Under the same conditions, though, humans' perceptual responses were dominated by global motion, which means that their responses were determined by a second brain mechanism that encodes global motion, whose nature is currently unknown.

J. Anthony Movshon, director of the Center for Neural Science and the paper's senior author, says that the work opens a window for further study: "While comprehending the specifics of this process requires more work, it's clear that motion perception does not depend on a single cortical brain area, but, rather, reflects the action and interaction of multiple mechanisms. We now have new tools to help us identify and study systems that are currently unknown."

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not rated yet Dec 05, 2011
wonder if my masters painting "yellow diamonds" the double or reverse after-image which is located in many of the psych 101 text books could in some way be analysed using humans. Or if you might be interested in checking out the visual motions of another after-image system which is quite visually active as the usage of brown leads to another visual set of perceptions which was not factored in the modern color theory when the booklet 'Color Interactions' 1952 Yale first or second edition.

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