Do you see what I see?

Apr 19 2004

A rose is a rose is a rose, but do we and the artist and poet all see the same flower in the same way? This age-old philosophical question has now been put to the test by scientists at the Weizmann Institute.

To compare individual perceptions of visual experiences, Prof. Rafael Malach and Uri Hasson, along with their colleagues in the Neurobiology Department, showed volunteers a segment of a movie (in this case, the classic western “the Good, the Bad and the Ugly”) while they were undergoing brain scans with state-of-the-art functional MRI equipment. These scans allowed the researchers to see which areas of the subjects’ brains were active during love scenes or gunfights.

Because a movie offers a wealth of different visual stimuli – scenery, aces, action, etc. – the researchers were able to track the brains’ response to a rich, dynamic scene. Showing the subjects a movie, rather than the typical visual stimuli used in such experiments – usually a series of carefully selected slides or photos – turned up some surprising results. Essentially, rather than presenting one type of stimulus and then looking for the response, the brain areas themselves were allowed to select their own fare from a smorgasbord of possibilities, and the scientists then took note of their selections.

What they found was a striking similarity between brain activity patterns in all the subjects; so much so that the patterns of one could be used to predict activity in other brains when viewing the same segment. “Despite our strong sense of individuality, such a high level of agreement between subjects implies that our brains ‘tick together’ when exposed to the same visual environment,” says Malach.

Surprisingly, reviewing the brain scans revealed that, if we all see literally the same movie, the active regions of our brains all view different movies. Because each area is activated by a specific kind of visual cue, it only picks up on those bits that “speak” directly to its specialized reference.

For instance, a region that is known to be involved with face recognition lit up only when close-ups appeared on the screen, while scenery elicited a response from another part of the brain that helps us navigate in three-dimensional space. The scientists noted a third area that seemed to be activated when actors performed delicate hand motions, which they think may be part of a network of brain regions that we use to understand the actions and intentions of others. “Thus,” says Malach, “while you perceive a single, whole movie, different regions of your brain are each processing a private motion picture of their own. The unified percept you experience is, in fact, the result of a tremendous, individualistic ‘jam session’ played by many different, highly specialized brain areas.”

Prof. Rafael Malach’s research is supported by the Mary Ralph Designated Philanthropic Fund; the James S. McDonnell Foundation; the Nella and Leon Benoziyo Center for Neurosciences; the Murray H. & Meyer Grodetsky Center for Research of Higher Brain Functions; and the Edith C. Blum Foundation Inc.