The lopsided brain: Attention bias is shared by humans...( When it comes to the world laid before ...)

When it comes to the world laid before us, our mind's eye has a bias. For reasons that are not entirely clear, during some tasks humans have a tendency to devote more visual attention to the left side of the visual world than the right side, a phenomenon known as pseudoneglect. Researchers now report that pseudoneglect is not restricted to humans but is shared by birds, suggesting not only that brain structures thought to play a requisite role in pseudoneglect may not actually be essential for this phenomenon, but also that pseudoneglect may reflect evolutionary adaptations that allow animals to devote attention to multiple aspects of their environment.

The findings are reported in the May 24 issue of Current Biology by Bettina Diekamp (now at Johns Hopkins University) and colleagues at Ruhr University, Bochum, Germany; the University of Padova, Italy; and The University of Trieste, Italy.

It has been known for some time that human patients who have suffered injury to the brain's right hemisphere can experience a much more severe bias in their spatial attention--spatial hemineglect--in which the entire left side of the visual world seems nonexistent as the brain performs spatial tasks. In a classic example, a patient asked to draw a daisy can only manage to put petals on the right side of her drawing.

The more subtle leftward bias in attention present in healthy humans likely has to do with asymmetries in the wiring of the brain's attention in the two hemispheres; the new finding in birds offers some insight into how and why this might be.

In the new work, researchers tested two bird species, the domestic chick and the pigeon, for their performance on a task in which they were allowed to freely peck at grains of food that were spread evenly in an area before them. Though the birds' bodies were positioned at the midline of the search area, both chicks and pigeons showed a considerable leftward bias in pecking. The experiment i
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Contact: Heidi Hardman
hhardman@cell.com
1-617-397-2879
Cell Press
23-May-2005

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