The Corpus Callosum Makes the Headlines
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Well, Sort of

Psychopathic Brains Are Hardwired That Way

By rickyjames, Section News Posted on Fri Mar 12th, 2004 at 08:10:46 AM PST

From: SciScoop, also appears on ScienceDaily,  adapted from a news release  issued by University Of Southern California.

This article deals with the research of Adrian Raine, Ph.D., who is the Robert Grandford Wright Professor and Professor of Psychology at USC; he has devoted his career to the study of the biological basis of Antisocial Personality Disorder (APD.)  For a quick overview of his work, you can go the the USC site and search on the string "Adrian Raine". 

Dr. Raine has focused his research on two parts of the brain: the hippocampus, a portion of the temporal lobe that regulates aggression and transfers information into memory; and the corpus callosum (CC), a bridge of nerve fibers that connects the cerebral hemispheres.

"Scientists have implicated different brain regions with respect to antisocial and aggressive behavior, and all are important and relevant," Raine said.

"But it goes beyond that to the wiring. Unless these parts of the brain are properly wired together, they'll never communicate effectively. They'll never result in appropriate behavior," he said.

Dr. Raine describes the key behavioral characteristics of persons who exhibit chronic sociopathic behavior.  (See this link  for an overview of the current conceptualization of Antisocial Personality Disorder.)  He is quoted in the article as saying:

"They are glib. They use words well and can be charming. That lures people into their devious net," Raine said. "Psychopaths can be the life of the party for a few minutes or a few hours, and it can actually be a wonderful experience brushing shoulders with them. It's when you get to know them in the long term that you begin to see that they are not what they appear to be."

This is something I wrote about in the first two posts (1  2) on The Corpus Callosum.  It is my opinion that the world would be a better place if all the non-narcisistic, non-antisocial people could recognize sociopathic behaviors more readily, so I often write about this topic.  Naturally, when I encountered a story about sociopathy AND the corpus callosum, I decided to report on it and add some background information and miscellaneous commentary.  The USC press release, and the articles that echo it, refer to two separate studies.  One study focused on the hippocampus; the other focused on the corpus callosum.

The one pertaining to the corpus callosum was published originally in Arch Gen Psychiatry. 2003;60:1134-1142.  What the authors did was to get a group of people, do personality tests on them, then match persons with APD with a control group without APD.  They used MRI to get detailed measurements of the size and shape of the corpus callosum, then analyzed the data to see if there were any corellations.  They also did some tests to see how much message traffic traversed the CC.

What they found is that the CC is longer (from front to back), thinner (from top to bottom), and has a greater cross-sectional area in persons with APD.  They also found that there was a larger amount of information going back and forth between the two hemispheres of the brain, in persons with APD. They hypothesized that the greater area is due to either an unusual interruption in the normal pruning process, whereby nerve cells are destroyed in the developmental process; or that there is greater myelination.  Since they could not do autopsies, they could not tell which explanation is correct.  Of course it would be possible to generate other hypotheses, but the two mentioned here seem the most likely. 

At first, the finding that there is more interhemispheric communication in persons with the disorder may seem counterintuitive.  But in brain science, it is fairly common that you see a higher amount of brain activity in a certain area in a person with a disorder as compared to a person without a disorder.  The significance of this is not known.  It may be that the extra activity is an attempt to compensate for a defect, or that it is essentially wasted, nonproductive activity, or something like that. 

In the case of sociopathy, it could be that there is extra activity in the corpus callosum because of all the scheming that a sociopath does, seemingly automatically.  An example would be a person who lies just as easily as telling the truth.  It may be that it takes more thinking to live your life like that.  It will be interesting to see if anyone is able to figure out exactly what is going on with the extra communication between the hemispheres.