How Our Brain Understands Pictures

By Roland Piquepaille

How is it possible that we perceive our world in 3D when our eyes only register 2D images? And how do we decide in a millisecond if something in front of us is a bouquet of flowers or a painting? Researchers from Johns Hopkins University think they know how our brain is analyzing pictures. They say that their research "answers the century-old question of the basis of subconscious processes in visual perception." According to the researchers, we're capable to "process visual information automatically and independently of what we know, think or expect." This research might lead to future treatments of human brain disorders. Read more...

Here is the introduction of the Johns Hopkins University news release.

The figure is famous: a deceptively simple line drawing that at first glance resembles a vase and, at the next, a pair of human faces in profile. When you look at this figure, your brain must rapidly decide what the various lines denote. Are they the outlines of the vase or the borders of two faces? How does your brain decide?

Below is an illustration describing the problem of interpreting 2D images in terms of objects in a 3D world (Credit: Johns Hopkins University).

Images are composed of regions that correspond to objects in space (A). The boundaries of these regions are generally the contours of objects that occlude more distant parts of the scene (occluding contours). To interpret images successfully, the visual system has to detect these contours and link them to the occluding regions. (B) The light textured region is generally perceived as a tilted square on a dark background, and the light-dark border as the contour of the square. But the display is ambiguous: the square could be a window. (C) The concept of border ownership. The interpretation of a 2D display depends on how the contrast borders are assigned (top). Consider the border marked by a black dot: if the border is assigned left, the square is an object in front of a dark background; if the border is assigned right, the square becomes a piece of background that is seen through a window. Given flat displays without depth cues, the visual system assumes the object interpretation.

The above image and legend come from a paper recently published by Neuron, "Figure and Ground in the Visual Cortex: V2 Combines Stereoscopic Cues with Gestalt Rules." Here is a link to the full paper (PDF format, 12 pages, 323 KB).

Now, let's return to the original news release for more explanations.

"Our paper answers the century-old question of the basis of subconscious processes in visual perception, specifically, the phenomenon of figure-ground organization," said Rudiger von der Heydt, a professor in the Zanvyl Krieger Mind/Brain Institute.

The report, based on recordings of nerve cells in the visual cortex of macaque monkeys, suggests that this automatic processing of images is repeated each time an individual looks at something new, usually three to four times per second. What's more, the brain provides what von der Heydt calls "a sophisticated program" to select and process the information that is relevant at any given moment.

But the researchers recognize that there are still lots of work to do before treating human brain disorders. Their current research needs to be "complemented by new brain imaging techniques, traditional psychophysics, psychology and computational and theoretical neuroscience."

Sources: Johns Hopkins University news release, August 9, 2005; and various web sites

Related stories can be found in the following categories.

• Medicine
  
• Psychology
  
• Science
  
• Vision and Visualization Apps
  

And remember that comments are no longer accepted here because of a vandal. If you want to tell me something about this post, please go to the bottom right of this page and send me an e-mail.