Featured Research

from universities, journals, and other organizations

Finding the place where the brain creates illusory shapes and surfaces

Date:
September 30, 2013
Source:
Vanderbilt University
Summary:
Neuroscientists have identified the location in the brain's visual cortex responsible for generating a common perceptual illusion: Seeing shapes and surfaces that don't really exist when viewing a fragmented background.

A Kanizsa square
Credit: Courtesy of D. Alan Stubbs, University of Maine

The logo of the 1984 Los Angeles Olympics includes red, white and blue stars, but the white star is not really there: It is an illusion. Similarly, the "S" in the USA Network logo is wholly illusory.

Related Articles


Both of these logos take advantage of a common perceptual illusion where the brain, when viewing a fragmented background, frequently sees shapes and surfaces that don't really exist.

"It's hallucinating without taking drugs," said Alexander Maier, assistant professor of psychology at Vanderbilt University, who headed a team of neuroscientists who has pinpointed the area of the brain that is responsible for these "illusory contours."

In the Sept. 30 online Early Edition of the Proceedings of the National Academy of Sciences, Maier's team reported that they have discovered groups of neurons in a region of the visual cortex called V4 that fire when an individual is viewing a pattern that produces such an illusion and remain quiescent when viewing an almost identical pattern that doesn't.

Studies have shown that a diverse range of species, including monkeys, cats, owls, goldfish and even honeybees perceive these illusory contours. This has led scientists to propose that they are the byproduct of methods that the brain has evolved to spot predators or prey hiding in the bushes, a capability with considerable survival value.

Although scientists discovered illusory contours more than a century ago, it is only in the last 30 years that they have begun studying them because they reveal the internal mechanisms that the brain uses to interpret sensory input.

In mammals, visual stimuli is processed in the back of the brain in an area called the visual cortex. Efforts to map tthis area have found that it is made up of five different regions at the back of brain (labeled V1 to V5.)

The primary visual cortex, V1, takes the stimuli coming from the eyes and sorts it by a variety of basic properties, including orientation, color and spatial variation. It also splits the information into two pathways, called the dorsal and ventral streams.

From V1, both streams are routed to the second major area of the visual cortex. V2 performs many of the same functions as V1 but adds some more complex processing, such as recognizing the disparities in the signals coming from the two eyes that produce binocular vision.

From V2, one pathway, sometimes called the "Where Pathway," goes to V5 and is associated with object location and motion detection. The other pathway, sometimes called the "What Pathway," goes to V4 and is associated with object representation and form recognition.

"Studies have shown that V4 is involved in both object recognition and visual attention, so we thought it might also be involved with illusory contours," said Michele Cox, the Vanderbilt graduate student who is first author on the study.

First, the researchers searched for the neurons in V4 that were associated with different locations in the retinas of macaque monkeys. Once these maps were complete, they rewarded the monkeys for staring at a screen containing an example of an illusory contour called a Kanizsa square. This consists of four "Pac-Man" figures with their "mouths" oriented to form the corners of a square. When black Pac-Men are placed on a white background, the brain creates a bright white square connecting them.

While the monkeys were looking at the Kanizsa square, the researchers discovered that the neurons that represented the area in the middle of the Pac-Men, the area covered by the illusory square, began firing. However, when the monkeys viewed the same four Pac-Men with their mouths facing outward -- an orientation that doesn't produce the illusion -- these central neurons remained silent.

"Basically, the brain is acting like a detective," said Maier. "It is responding to cues in the environment and making its best guesses about how they fit together. In the case of these illusions, however, it comes to an incorrect conclusion."


Story Source:

The above story is based on materials provided by Vanderbilt University. Note: Materials may be edited for content and length.


Cite This Page:

Vanderbilt University. "Finding the place where the brain creates illusory shapes and surfaces." ScienceDaily. ScienceDaily, 30 September 2013. <www.sciencedaily.com/releases/2013/09/130930152729.htm>.
Vanderbilt University. (2013, September 30). Finding the place where the brain creates illusory shapes and surfaces. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2013/09/130930152729.htm
Vanderbilt University. "Finding the place where the brain creates illusory shapes and surfaces." ScienceDaily. www.sciencedaily.com/releases/2013/09/130930152729.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Kids Die While Under Protective Services

Kids Die While Under Protective Services

AP (Dec. 18, 2014) As part of a six-month investigation of child maltreatment deaths, the AP found that hundreds of deaths from horrific abuse and neglect could have been prevented. AP's Haven Daley reports. (Dec. 18) Video provided by AP
Powered by NewsLook.com
UN: Up to One Million Facing Hunger in Ebola-Hit Countries

UN: Up to One Million Facing Hunger in Ebola-Hit Countries

AFP (Dec. 17, 2014) Border closures, quarantines and crop losses in West African nations battling the Ebola virus could lead to as many as one million people going hungry, UN food agencies said on Wednesday. Duration: 00:52 Video provided by AFP
Powered by NewsLook.com
When You Lose Weight, This Is Where The Fat Goes

When You Lose Weight, This Is Where The Fat Goes

Newsy (Dec. 17, 2014) Can fat disappear into thin air? New research finds that during weight loss, over 80 percent of a person's fat molecules escape through the lungs. Video provided by Newsy
Powered by NewsLook.com
Why Your Boss Should Let You Sleep In

Why Your Boss Should Let You Sleep In

Newsy (Dec. 17, 2014) According to research out of the University of Pennsylvania, waking up for work is the biggest factor that causes Americans to lose sleep. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins