The Cerebellum Question
“In the history of autism research, pretty much every brain region you can think of has been put forth as possibly being involved,” said Dr. Greg Allen, a neuroscientist in the College of Education’s Department of Educational Psychology, “because autism is so complex. Things come in and out of style as far as what people are studying.”
Theories may come and go like the seasons but during the 20 years he’s been studying autism Allen’s focal point – the cerebellum – has remained the same.
Tucked under the squiggly cerebrum, the cerebellum – Latin for “little brain” – is believed to play a pivotal role in motor control and cognitive functions such as attention and language.
“Since I was a graduate student my research has been in parallel areas that feed into each other,” said Allen. “One is to understand what the cerebellum does and one is to understand its role in autism.”
For many years the notion that the cerebellum might play a part in the development of autism was a controversial subject. The theory still attracts its share of naysayers but, thanks to tools such as Magnetic Resonance Imaging (MRI) and ultrasounds, Allen is on the way to demonstrating an important role for the cerebellum in autism.
“Currently, about one percent of children are now being diagnosed with an autism spectrum disorder.”
“I started graduate school two years after functional magnetic resonance imaging was discovered,” he said. Suddenly scientists were using MRI to measure all kinds of changes in brain activity during various tasks and treasure troves of new data were becoming available.
“One of the really perplexing things coming out of these studies was that the cerebellum was almost always active, regardless of task. And you couldn’t explain it all by just the fact that the subject was moving around because people move very little in an MRI scanner. That, in part, led to this revolution in thinking about what the cerebellum was doing, which has also been a focus of my research.”
Because of these results, Allen and others came to see the cerebellum as more than just a coordinator of movement. He saw the delicate heart-shaped section of brain as potentially playing a role in the symptoms of autism. Data were being unveiled from his and other scientists’ research suggesting this was the case.
To obtain these data Allen uses four distinct MRI approaches to investigate differences between normal and autistic brains. Two look at brain structure while the other pair examines brain function.
“On the structural side we do an MRI that’s more akin to the kind you might get if you’re prescribed to go get a scan of some part of your body,” he explained. “Looking at a very high-resolution image of the cerebellum allows us to measure particular parts of it, distinguish between different types of tissue and get a better idea, anatomically, what the differences are in autism.”
On the other side of the coin, a method called functional connectivity MRI examines the three major pathways that lead in and out of the cerebellum.
“It looks at different regions and how well they’re working together, their fluctuations and signals across time,” said Allen. “You can put that information together with the structure to get an overall picture of the connections between regions.”
Studies examining underlying changes in connectivity and communication have been a hot area in autism studies in recent years, according to Allen. These investigative techniques have led to a revolution in thinking about the cerebellum.
“I’m using these tools to look at what might be getting in the way of that connection with other parts of the brain,” he said. “So it’s not just about what’s happening within the cerebellum but also what’s happening between the cerebellum and other areas.”
Asked about other ways his investigative approach differs from typical methods, Allen points to his current work with prenatal ultrasound images of the cerebellum. Although some scientists argue against the relevance of the cerebellum to autism because differences may not always be clear until later in life, Allen states there is plenty of evidence to suggest that those differences show up as early as before birth.
A key bit of information to consider when arguing that cerebellum differences are relevant to autism is determining when they first appear, which is where prenatal ultrasound enters the picture.
Allen is using ultrasound images to examine the cerebella of developing fetuses in the womb to better understand early cerebellar development in autism. “It’s a simple, standard measurement,” he said. “There are norms for it, so you can go in and look at it and say, ‘Okay, that cerebellum is small or large for that child’s age.’” Allen is now in the process of acquiring these measurements from children who were later diagnosed with autism in order to address the important question of whether cerebellar differences are present prenatally.
Despite all the available research and advanced investigative methods, the future of autism treatment remains murky, at least for the time being. Successful current solutions focus on changing things at the behavioral level.
Allen would like to understand more about how these behavioral methods are changing things at the brain level.
“Ultimately, we’d like to think there are treatments that will target particular brain regions and stimulate those regions at certain times of development to help build connections,” said Allen.