New research provides more evidence that chimpanzee brains are human-like in terms of the links between brain asymmetry, language and right- or left-handedness.

In one study, researchers used magnetic resonance imaging to study two key structures -- the hippocampus and amygdala -- in the brains of 60 chimpanzees. Both structures are part of the limbic system.

The MRI images revealed that the right side of the hippocampus was much larger than the left side. This asymmetry was more pronounced in males. Human hippocampi are also asymmetrical in the same way.

The amygdalas of the chimps were symmetrical, the same as in humans.

"The limbic system asymmetries advance the position that asymmetries are fundamental aspects of the nervous system of all primates, and apply to more primitive systems in the brain," researcher William Hopkins, of the Yerkes National Primate Research Center in Atlanta, said in a prepared statement.

These asymmetries influence behaviors such as facial expression and spatial memory, Hopkins said.

A second study found the first-ever evidence of an association between hand preference and asymmetries in three regions of the chimpanzee brain cortex.

The findings appear in the December issue of Behavioral Neuroscience.

Reference Source 101
December 7, 2004

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