How do we make sense of what we see?

November 19, 2007
How do we make sense of what we see?
Copyright: M.C. Escher

M.C. Escher’s ambiguous drawings transfix us: Are those black birds flying against a white sky or white birds soaring out of a black sky? Which side is up on those crazy staircases?

Lines in Escher's drawings can seem to be part of either of two different shapes. How does our brain decide which of those shapes to "see?" In a situation where the visual information provided is ambiguous -- whether we are looking at Escher's art or looking at, say, a forest -- how do our brains settle on just one interpretation?

In a study published this month in Nature Neuroscience, researchers at The Johns Hopkins University demonstrate that brains do so by way of a mechanism in a region of the visual cortex called V2.

That mechanism, the researchers say, identifies "figure" and "background" regions of an image, provides a structure for paying attention to only one of those two regions at a time and assigns shapes to the collections of foreground "figure" lines that we see.

“What we found is that V2 generates a foreground-background map for each image registered by the eyes," said Rudiger von der Heydt, a neuroscientist, professor in the university's Zanvyl Krieger Mind/Brain Institute and lead author on the paper. "Contours are assigned to the foreground regions, and V2 does this automatically within a tenth of a second.”

The study was based on recordings of the activity of nerve cells in the V2 region in the brain of macaques, whose visual systems are much like that of humans. V2 is roughly the size of a microcassette and is located in the very back of the brain. Von der Heydt said the foreground-background “map” generated by V2 also provides the structure for conscious perception in humans.

“Because of their complexity, images of natural scenes generally have many possible interpretations, not just two, like in Escher’s drawings,” he said. “In most cases, they contain a variety of cues that could be used to identify fore- and background, but oftentimes, these cues contradict each other. The V2 mechanism combines these cues efficiently and provides us immediately with a rough sketch of the scene.”

Von der Heydt called the mechanism "primitive" but generally reliable. It can also, he said, be overridden by decision of the conscious mind.

“Our experiments show that the brain can also command the V2 mechanism to interpret the image in another way," he said. "This explains why, in Escher’s drawings, we can switch deliberately" to see either the white birds or the dark birds, or to see either side of the staircase as facing "up."

The mechanism revealed by this study is part of a system that enables us to search for objects in cluttered scenes, so we can attend to the object of our choice and even reach out and grasp it.

“We can do all of this without effort, thanks to a neural machine that generates visual object representations in the brain,” von der Heydt said. “Better yet, we can access these representations in the way we need for each specific task. Unfortunately, how this ‘machine’ works is still a mystery to us. But discovering this mechanism that so efficiently links our attention to figure-ground organization is a step toward understanding this amazing machine.”

Understanding how this brain function works is more than just interesting: It also could assist researchers in unraveling the causes of – and perhaps identifying treatment for – visual disorders such as dyslexia.

Source: Johns Hopkins University

Related Stories

Recommended for you

Engineered protein treatment found to reduce obesity in mice, rats and primates

October 19, 2017
(Medical Xpress)—A team of researchers with pharmaceutical company Amgen Inc. report that an engineered version of a protein naturally found in the body caused test mice, rats and cynomolgus monkeys to lose weight. In their ...

New procedure enables cultivation of human brain sections in the petri dish

October 19, 2017
Researchers at the University of Tübingen have become the first to keep human brain tissue alive outside the body for several weeks. The researchers, headed by Dr. Niklas Schwarz, Dr. Henner Koch and Dr. Thomas Wuttke at ...

Cancer drug found to offer promising results in treating sepsis in test mice

October 19, 2017
(Medical Xpress)—A combined team of researchers from China and the U.S. has found that a drug commonly used to treat lung cancer in humans offers a degree of protection against sepsis in test mice. In their paper published ...

Study reveals key molecular link in major cell growth pathway

October 19, 2017
A team of scientists led by Whitehead Institute has uncovered a surprising molecular link that connects how cells regulate growth with how they sense and make available the nutrients required for growth. Their work, which ...

Tracing cell death pathway points to drug targets for brain damage, kidney injury, asthma

October 19, 2017
University of Pittsburgh scientists are unlocking the complexities of a recently discovered cell death process that plays a key role in health and disease, and new findings link their discovery to asthma, kidney injury and ...

Inflammation trains the skin to heal faster

October 18, 2017
Scars may fade, but the skin remembers. New research from The Rockefeller University reveals that wounds or other harmful, inflammation-provoking experiences impart long-lasting memories to stem cells residing in the skin, ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

MongHTan,PhD
1 / 5 (1) Nov 19, 2007
"We can do all of this without effort, thanks to a neural machine that generates visual object representations in the brain," von der Heydt said. "Better yet, we can access these representations in the way we need for each specific task. Unfortunately, how this 'machine' works is still a mystery to us. But discovering this mechanism that so efficiently links our attention to figure-ground organization is a step toward understanding this amazing machine."


This mechanism is called "Memophorescenicity" that I pointed out in a related article here:

http://www.physor...191.html

Thank you all!
MongHTan,PhD
not rated yet Nov 19, 2007
Somehow the above URL doesn't work; let me try again:

http://www.physor...191.html

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.