How Do Our Brains Determine What Image We See?

How do our eyes and our brain determine what we see? The famous artist, M. C. Escher was a master at creating drawings that presented two images at one time. When what we are looking at is ambiguous, whether we are looking at a forest or one of Escher's paintings, what determines which part of the image that we see?

In a recent press release, researchers at Johns Hopkins University set about to answer that very question. It is important because knowing how our brain functions at this level may lead to advances in identifying, and hopefully eventually treating, disorders that are related to our vision such as dyslexia.

The researchers discovered that there is a specific region in our visual cortex, a part of our brain, which is responsible for interpreting what we are seeing. This special region is called the V2.

The V2 assigns different shapes and structures for the images that are presented to us, allowing us to see only one of the two images at a time. It identifies areas of what we are seeing, labeling some backgrounds, and other foregrounds. This process occurs so rapidly that we are not even aware of it.

When we actually 'see' the image, our brain tells us that there is only one image. We can, however, override what our brain 'sees,' by telling our brain to focus on the other part of the image. When we do this, we 'see' the other part of the image.

This process also lets us see objects presented to us in cluttered scenes so that we can 'see' it, move toward it, and even touch it.

"Because of their complexity, images of natural scenes generally have many possible interpretations, not just two, like in Escher's drawings. 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," said Rudiger von der Heydt, a neuroscientist, and professor in the university's Zanvyl Krieger Mind/Brain Institute.

About the study
Researchers based this study on the brain activity of macaques. A macaque is a specific breed of monkey that has visual systems that are very close to that of humans. The researchers recorded activity that occurred in the nerve cells of the V2 region in their brains.

Von der Heydt said that the V2 is located in the back of the human brain, and is about the size of a microcassette tape.

Sources:
http://www.jhu.edu/news_info/news/home07/nov07/vonderheydt.html
http://www.mcescher.com/
http://en.wikipedia.org/wiki/M._C._Escher
http://en.wikipedia.org/wiki/Macaque