There seems to be a flood of brain research lately that helps illuminate how the brain responds to social stimuli.
An intriguing new area is looking at two kinds of tissue in the brain: white matter and gray matter. We usually think of gray matter as the stuff we use for cognition; more grey matter tends to equal a higher IQ, for example. White matter, on the other hand, is the connective nerve tissue thought to be used for "wiring together" different parts of the brain.
Of course, it's not that simple. Too much gray matter in some regions has been linked to trauma.
Two studies released today looked at the relationship between volume of white or gray matter and behavior.
First, a team led by Manzar Ashtari of the Children's Hospital of Philadelphia in Pennsylvania looked at the brains of autistic kids. They found more gray matter than normal in parts of the brain dealing with social interactions. They think this could be related to abnormal function of the mirror neuron system.
Mirror neurons are thought to be special kinds of nerve cells that fire when we watch others. It's still speculative in humans, but they've found that monkeys have what they call mirror neuron regions that fire when the monkey watches a researcher pick up a cup. This might be related to empathy, the ability to literally put oneself in another's place. See Mirror Neurons, Oxytocin and Autism for more.
According to the Science Daily story,
"In the normal brain, larger amounts of gray matter are associated with higher IQs," Dr. Ashtari said. "But in the autistic brain, increased gray matter does not correspond to IQ, because this gray matter is not functioning properly."The autistic children also evidenced a significant decrease of gray matter in the right amygdala region that correlated with severity of social impairment. Children with lower gray matter volumes in this area of the brain had lower scores on reciprocity and social interaction measures.
Another study by James Cantor of the Centre for Addiction and Mental Health in Toronto found significantly less white matter in the brains of pedophiles than in the brains of non-sexual offenders. The article says,
The study, published in the Journal of Psychiatry Research, challenges the commonly held belief that pedophilia is brought on by childhood trauma or abuse. This finding is the strongest evidence yet that pedophilia is instead the result of a problem in brain development.
I don't understand why they draw this conclusion. Plenty of studies have shown abnormalities in brain development in children who've been neglected, abused or traumatized. In fact, Victor Carrion of Stanford has found more gray matter in the prefrontal cortexes of the brains of children with PTSD. He's also found decreased total volume in the PFCs of adults and children with PTSD.
He recently told me that it's difficult to identify exactly what these differences mean when it comes to brain function and behavior. He said, "It seems like in some regions, there's a problem if you have more volume ... in others, it's problematic if you don't have enough."
It seems to me that Cantor's study provides further evidence for two things: that early trauma affects brain development, and that this abnormal brain development leads to abnormal behavior later.
I've contacted the Centre for Addiction and Mental Health to more information on this statement. I'll post if and when they get back to me.
