ATLANTA -- Hand preference and language go hand-in-hand, or do they? According to researchers at the Yerkes National Primate Research Center of Emory University, handedness is not associated with the language area of the brain, as has been the accepted scientific thought throughout history. Rather, handedness is associated with the KNOB, the area of the brain known for controlling hand movements in primates and, now, for determining handedness in chimpanzees. The researchers report their groundbreaking findings in the December 6 issue of Behavioral Neuroscience.
According to Bill Hopkins, PhD, research associate in the Division of Psychobiology at the Yerkes Research Center and the study's lead investigator, "The dominant scientific view has linked hand preference in humans with the area of the brain that controls language. After observing hand preference in chimpanzees, which have no comparable language capabilities, we concluded there must be another reason for handedness. Because human and chimpanzee brain structures are so similar, we wanted to determine if human handedness evolved from an area of the brain other than the language area."
Hopkins and his research team coordinated a series of motor tasks with chimpanzees to determine each animal's hand preference and then looked at magnetic resonance imaging (MRI) scans of the animals' brains. They found asymmetries in the KNOB and in the area that is homologous to the human language brain region. A detailed review of the data showed the asymmetries in the KNOB corresponded to right- and left-handedness whereas the asymmetries in the language area did not, leading the researchers to conclude handedness is linked explicitly to the KNOB and not other brain regions.
In a separate study, which is published in the same issue of Behavioral Neuroscience, Dr. Hopkins' team supported their findings about asymmetry by confirming that the brain structure of chimpanzees is similar to the brain structure of humans. Using MRI scans of the chimpanzees' brains, the researchers discovered asymmetries in each brain hemisphere, a characteristic previously thought unique to humans.
"For years, researchers thought asymmetry is part of what distinguished the human brain from that of chimpanzees, but our results challenge that theory," said Dr. Hopkins.
To further explore what distinguishes the human brain from those of other species, Yerkes researchers are conducting a variety of studies to identify the changes in gene activity and biochemistry that occurred during human brain evolution as well as related changes in the connectivity and functions of the brain.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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