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By Dayo Akinwande

Our understanding of autism has certainly come a long way. According to the National Autism Association (NAA), a theory about “refrigerator mothers” as the primary cause of autism was widely held from the 1950s to as recently as the early 1970s. This myth, which claimed that mothers with autistic children did not love their children enough and consequently caused them to revert into their own, socially disabled worlds, has eventually and gladly been debunked, as have many other myths about autism (e.g., that autistic children are unloving or unemotional). Our understanding of how to nurture and facilitate the growth of autistic children has dramatically increased. However, there is still a bracing reality: Knowledge of an exact cause of the disease, and a potential cure, remains elusive.

Thankfully, the unique research of Dr. Benjamin Walker is making large strides in the right direction. Dr. Walker, an assistant professor in the Department of Psychology, is currently researching the biological changes in the brain and their connection to behavioral actions associated with autism.

Autism is a collection of brain development disorders characterized by deficits in social interaction and communication. Other core symptoms are behavioral features like hand flapping, toe walking, and a lack of awareness of the surrounding environment. These symptoms usually start to appear in children at around age 2 to 3 years.

“Autism is a spectrum disorder where there are a range of functions,” explains Dr. Walker. “Kids are impaired in certain things while not in others.”

Autism spectrum disorders range from autism itself to much milder forms of it, most specifically Pervasive Development Disorder – Not Otherwise Specified (PDD-NOS), which is often used to describe patients who, although exhibiting some symptoms of autism, are too social to be labeled autistic. Some autistic patients have great extremes in certain abilities—“neurofunnels transferred into one place,” as Dr. Walker describes it, referencing the scene in Rain Man where Dustin Hoffman’s character, who has autism, is able to make an instant and accurate count of the number of toothpicks he spills on the floor.

Dr. Walker explores how changes in the pre-natal/post-natal environment affect or trigger autism in humans. He is also concerned with whether autism has something to do with maternal infection during pregnancy or a hyperactive immune system during childhood. Current autism research suggests that the disease could be the result of an immune response against its own cells and tissues, similar to multiple sclerosis—the body, through its immune system, attacks its own nervous system. Or, it could be due to what Dr. Walker terms “opportunistic infections.” For instance, AIDS patients die of illnesses like pneumonia because of the weakening of the immune system by the HIV virus, not because of the virus itself. Similarly, there could be something that weakens the brain to the extent that it is left vulnerable to autism.

Because autism is a brain development disorder, it is essential to discover when brain activity starts and stops—during, or even after, pregnancy. Moreover, there needs to be a good model that shows how the brain is affected to produce autism. Dr. Walker seeks to determine the cause of autism by isolating a specific neural or cellular problem in the brain that activates autistic behavior. He begins by using clinical data gathered from the literature from children with autism that suggests an abnormality in the acetylcholine neurotransmitting system—something that may account for a reduction in social behavior.

“In our experiments, we take that clinical data and transfer it into rats,” says Dr. Walker. “We give rats a neurotoxin that targets those specific acetylcholine cells. So, for example, we deplete acetylcholine in the basal forebrain of the rat.”

Dr. Walker uses the rats whose brains have been altered to mimic the brain of a person with autism in a series of experiments to determine if the rats mirror the social behavior of people with autism. Such findings inform research on the specific areas of the brain that control the varying manifestations of autism along the spectrum.

“When we started many of these experiments, there were very few non-primate models of autism,” Dr. Walker says. “Now there are many more, but we are one of the few labs that routinely measure behavior development as it relates to autism.”

He currently uses three experiments to study the behavioral differences in control rats and altered rats (see related video). One is based on a structure that has three connected chambers, with a normal rat on the far left, familiar bedding on the far right, and a rat—control or altered—in the middle. When Dr. Walker measured the amount of time each rat placed in the middle spent in each chamber, he discovered that the control rats spent more time with the normal rat than the altered ones. The finding that behavioral dissociations in the altered rats match with clinical data suggests that alterations in acetylcholine may be the basis for the clinical behavioral abnormalities seen in children with autism.

Another experiment—in which some, but not all, of the altered rats poked their noses into holes made in the bottom of a container—confirms that each type of autism produces different behavioral symptoms. A third suggests that rats with abnormalities in the acetylcholine neurotransmitting system do not startle at sounds in the way control rats do, demonstrating the decrease in awareness of surroundings that many people with autism exhibit.

Rats are an important part of Dr. Walker’s research because of their similarities to humans in terms of the workings of the neurons in the brain, which control behavior. Moreover, he is able to apply data he gathered in earlier research on epilepsy from seizures in rats. Dr. Walker’s work is all done under the auspices of the Georgetown University Animal Care and Use Committee.

His work on epilepsy was part of his post-doctorate research, which he conducted at Georgetown. Initially a Biology major in his undergraduate years, Dr. Walker took a different study path after enrolling in his first Psychology course. He earned a Master’s degree and Ph.D. in Psychobiology from the University of Virginia before coming to Georgetown. His love for studying the brain and how it affects behavior and for the Georgetown community come together in his current position.

“What I really love is teaching new students,” he says. “The students here at Georgetown are great. They’re inquisitive, they’re bright, and I have a really good time with them.”

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