Posted on 09/05/2001 3:14:06 PM PDT by Nebullis
A defining difference between man and non-human primates has been found in the circuitry of brain cells involved in language, according to researchers at the Medical College of Georgia.
Their findings belie the notion that the primary difference between man, monkey and chimpanzee is the size of the brain and opens up a new area of study that may explain man's capacity for complex communication, they say.
They also say this circuitry may be what goes awry in still unexplained conditions that affect language, such as schizophrenia, autism and even epilepsy.
"Language is something that makes us different from other species; now we have found a structural correlation," said Dr. Manuel F. Casanova, psychiatrist and neurologist at MCG and the Department of Veterans Affairs Medical Center in Augusta.
"We are trying to understand what makes the human brain different from non-human primates," said Dr. Daniel Buxhoeveden, physical anthropologist at MCG. "We also are trying to understand the pathology of diseases of the brain that are not understandable by classical methods. We think the difference is going to be in the way the brain is organized."
To study that organization, they have completed detailed computer analyses of a basic, functional unit of the human and non-human brain known as a minicolumn, a group of 80 to 100 cells and the wiring that connects them. Millions of these minicolumns are found throughout the brain; their studies focused on the minicolumns found in an area of the brain involved in language called the planum temporale.
There they found distinct, microscopic differences in the minicolumns of humans and non-human primates. They also found differences in the minicolumns in the right and left side of the brain in humans that weren't present in non-humans; previous studies found distinctive lateralization – or left-right differences – in humans and chimps. "These minicolumns are different in their structure in the human brain and also different in that they are lateralized, larger on the left side than on the right side of the brain," Dr. Buxhoeveden said. "We didn't find this in the chimpanzee or the monkey." In most humans, language function is housed on the left side of the brain, which would make the left-right differences found all the more pertinent, Dr. Casanova said.
These differences may explain man's capacity for the subtleties of communication – such as understanding concepts and formulating and expressing responses – compared to the non-human primates' more fundamental communication system.
Is there a doctor/anatomist/anthropologist out there who can either say I'm right or wrong?
The structure in question is the hyoid, a horseshoe-shaped bone resting freely in the throat, attached indirectly to the larynx, tongue, and base of the skull by ligaments and muscles. The hyoid is very fragile, and thus rarely found preserved as a fossil, even within relatively recent human remains. Despite decades of excavation at Kebara by researchers from Israel, France, and the United States, "It was a total fluke that this one was found in such excellent condition," according to Lyn Schepartz, a member of the excavation team and a professor of anthropology at the University of Cincinnati. This fossil, dated at 60,000 years old, represents the earliest complete hyoid in the fossil record anywhere in the world. The tiny hyoid may have huge implications for demonstrating the capacity for speech in fossil hominids. It is attached to the muscles controlling the tongue, and its delicate movement within the throat helps control the formulation of speech.[...]
http://www.fonz.org/zoogoer/zg1995/firstwords.htm
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