When you gaze out of a train, the scenery appears to move even after the train has stopped. Vision researchers have generally dismissed this type of after-affect as a perceptual glitch that happens only after extended viewing of particular types of images. But now a team of NYU/U.Rochester neuroscientists have found that such after-affects may occur constantly and may be a critical part of normal visual perception.
The team found evidence that the viewing any image for as little as .5 seconds causes an after-affect. Furthermore, the researchers have hypothesized that these rapidly occurring after-affects -- or perceptual adaptations, as they're known -- play a critical role in helping the brain to rapidly discern subtle differences in visual patterns.
The researchers report their results in the August 27th issue of Science in an article entitled "Rapid Adaptation in Visual Cortex to the Structure of Images." They report that when they presented visual patterns for viewing, neuronal activity in the visual cortex dropped precipitously within .5 seconds, and the neurons remained desensitized to the image for several seconds thereafter. However, exposure to a second image (even one that was only subtly different from the first) caused a high level of neuronal activity.
James R. Müller -- who is the main author of the article -- said, "Our evidence suggests that visual adaptation -- which has often been regarded as on odd glitch -- may actually be critical to normal visual perception. Because adaptation occurs so rapidly, it can develop even during the fleeting stops our eyes make when we scan an image, and this can help us distinguish small differences between the things we see on successive stops."
Coauthor Peter Lennie said, "Neuroscientists have long know that that first stage of the visual cortex analyzes images to identify features in them, but we are constantly being surprised by the sophistication of this analysis. Our work provides yet another illustration of the marvelous intricacy and efficiency of our perceptual machinery."
This research was supported by funding from the National Eye Institute.
James R. Müller is currently at the Stanford University School of Medicine. He was affiliated with the Center for Visual Science at the University of Rochester during the time of this research. Peter Lennie, who is a co-author of the article and supervised Müller's work at Rochester, is now a member of the faculty at NYU's center for Neural Science. Co-author Andrew B. Metha is at the Australian National University, and co-author John Kraskopf is at NYU's Center for Neural Science.
NYU's Center for Neural Science (CNS) is the focus for teaching and research in the brain sciences at NYU's Washington Square Campus. Formed in 1987, CNS has developed an international reputation for the quality of its research. The research interests of the faculty span a broad range of topics in neural science, and utilize techniques ranging from molecular and cellular analyses to fully integrated systems, computational, and cognitive studies.
The Center for Visual Science (CVS) at the University of Rochester is among the world's largest research centers dedicated to the study of visual perception. Currently CVS's 25 research laboratories are studying nearly all aspects of vision -- from its earliest stages, such as the encoding of spatial and temporal patterns of light by neurons in the retina, to its latest stages, such as the interaction between visual perception and memory. These laboratories employ a wide range of theoretical perspectives as well as a diversity of neuroscientific, behavorial and computational methodologies.
Journal
Science