LEFT brain, logical and intellectual. Right brain, emotional and creative. While many suspect self-help therapies stem from this simplification, many studies, especially of brain injuries, confirm that the two sides of the brain do have different processing styles.
The left brain excels at analytical, more focused tasks, while the right brain does better at tasks that involve the 鈥渂igger picture鈥�, such as understanding metaphors and recognising faces. So what accounts for these differences?
A team led by Isao Ito of Kyushu University in Fukoka, Japan, has just added an intriguing piece to the puzzle. They have discovered that in mice one kind of receptor on nerve cells is distributed differently on the right and left sides of the hippocampus, a region deep in the brain that is key to creating memories and learning (Science, vol 300, p 990). These NMDA receptors are vital for changing the strength of the connections between one nerve cell and the next, the basis of memory and learning (see Inside Science, 鈥淭his is your life鈥︹��).
Advertisement
On the right side, the Japanese team found more of a specific type of NMDA receptor on dendrites (the tree-like extensions of nerve cells) at the tip of the cell than at the base. The opposite pattern was true in the left hippocampus. How a nerve cell responds to an input depends on where it receives it, so that pattern could conceivably alter how memories are formed on the two sides.
Besides helping lay down memories, the hippocampus is the key to spatial learning 鈥� indeed, parts of the hippocampi of London cabbies are enlarged. But no one knows how receptor differences in the hippocampus might influence the processing styles of the brain鈥檚 cortex, the outermost layer that is key to complex thought processes.
At the very least, though, investigating the differences in right and left hippocampi could reveal what principles are operating in other parts of the brain, says Lesley Rogers, an expert on brain lateralisation at the University of New England in Armidale, Australia.
The findings also add to the evidence that left-right brain differences are not unique to humans and higher primates such as chimps. Lateralisation has been invoked to explain higher cognitive skills, but the discovery of numerous examples in non-primates makes this argument look increasingly hollow.