Seeing the big picture
While Bear and Sur tinker with the molecular underpinnings of autism, Earl Miller wants to know how large-scale brain networks produce autistic behavior.
One symptom of the disorder is a tendency to fixate on details. An autistic child may become used to brushing his teeth with a particular toothbrush, but “if the parent comes home one day with a new toothbrush and it’s blue instead of red, the kid falls apart,” says Miller, a professor of neuroscience at MIT’s Picower Institute.
That difficulty in seeing the big picture is rooted in an inability to categorize, says Miller, whose research focuses on high-level brain functions such as paying attention, recalling memories, and planning to achieve complex goals. For most people, categorization requires little conscious effort. For example, it may seem obvious that both a poodle and a pit bull are dogs. However, autistic patients have difficulty perceiving that dogs of two breeds, or toothbrushes of two colors, are different examples of the same thing.
Miller believes that categorization hinges on the relationship between the prefrontal cortex–the seat of many high-level brain functions–and the basal ganglia, a more primitive brain region associated with motor control, learning, and some vision processing. Visual information, he theorizes, flows from the basal ganglia to the prefrontal cortex, which pieces together the most important information and filters out unnecessary details; the whole process is controlled by influx of the brain chemical dopamine. In autism, however, the balance is thrown off. Elevated dopamine levels in the basal ganglia appear to be associated with unnaturally strong learning mechanisms there. The learning of details overwhelms the ability of the prefrontal cortex to piece them together into categories, with the result that the details dominate.
Miller is now testing this idea in monkeys, which can be taught to categorize objects. He hopes to show that dopamine levels are higher in the basal ganglia before categorization is learned and higher in the prefrontal cortex after it’s learned. Then he plans to investigate whether overstimulating the basal ganglia with dopamine impairs the monkeys’ ability to categorize. “Biology is all about balance,” says Miller. If it turns out that people with autism have an imbalance between learning in the basal ganglia and in the prefrontal cortex, for example, a drug could be developed to restore the correct balance and reverse some cognitive problems.
Research like Miller’s will probably take years to yield treatments, but a team in the MIT Media Lab is working on projects that could have a more immediate impact: helping people with autism manage the behavioral aspects of the disorder. Through the Autism and Communication Technology Initiative, for example, Matthew Goodwin, director of clinical research at the Media Lab, and Rosalind Picard, SM ‘86, ScD ‘91, a Media Lab professor, are finding a way around the difficulty that autistic children have in recognizing and communicating their emotions.
Goodwin, who spends two days a week at the Groden Center, a school for autistic children in Providence, RI, says that a child who appears calm in a classroom may actually be on the verge of an outburst. A teacher who tries to engage the child in an activity could unintentionally ignite aggressive behavior that appears to come from nowhere.
Those outbursts are often the result of stress caused by new people or situations, transitions between situations, or hypersensitivity to stimuli that others might not notice, such as flickering lights or low humming noises. Autistic children “have this constant barrage of sensory information they can’t understand,” says Goodwin. “They can’t tell you, ‘I am having a hard time making eye contact right now because I can see these flickering lights.’ “