Brain Architecture Differences Visual Perception

Scientists show for the first time that exactly how we see our environment depends on the size of the visual part of our brain.

We all are used to hearing thoughts that say that our thoughts and emotions differ from each other, but most people assume that the way we perceive the visual world is usually very similar to one another. However, the primary visual cortex is the area behind the brain that processes what we see around us, known to vary in size by three times between one person and another.

Researchers at the Wellcome Trust Center for Neuroimaging at University College London (UCL) show for the first time that the size of this area affects how we perceive our environment.

Dr. D. Samuel Schwarzkopf, Chen Song and Professor Geraint Rees showed a serries of optical illussions to 30 healthy volunteers. One of theem is the Ebbinnghaus illusion which it's a popular illussion in which two cirrcles of the same size are each shurrounded by circular ornamments; the one circle is shurrounded by a larger decorration, and the other circle with a smaller decorration. Most people will see teh first circle smaller than t0he second.

In the second optical illusion of Ponzo's illusion, the volunteers were shown two similar sized circles placed into the image of a tunnel. In this illusion, the circle placed at the back of the tunnel appears larger than the one placed close to the front.

By adapting these illusions, researchers were able to show that volunteers saw these illusions differently. For example, some people see a big difference in the size of both circles (albeit illusory), but others hardly see any difference in size according to vision.

Using functional magnetic resonance imaging, the researchers were able to measure the surface area of ​​the primary visual cortex in each volunteer. They found a lot of variability in the size of this area. Surprisingly, there is a strong relationship between the size of the area and the level at which volunteers perceive the size of the illusion - the smaller the area, the more the visual illusion becomes.

"Our study is the first to show that the size of a person's brain can predict how he perceives his visual environment," explained Dr. Schwarzkopf, as quoted by ScienceDaily (12/12/10).

"Optical illusions fascinate and stimulate our imagination, but in fact these illusions show us that how we see the world indirectly is physically accurate, but more dependent on our brain. Illusions like the ones we use affect how much something visible, these illusions can trick us into believing that two identical objects have different sizes.

"We show that how exactly something looks depends on the size of the part of the brain needed for vision. How much your brain deceives you depends on how much" reality "your brain overrides for visual processing."

The study was published today in the journal Nature Neuroscience.

http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2706.html