Before you started to pick up this newspaper, your brain carefully calculated the exact force necessary to lift it. It also told your fingers how to turn the pages, how close to bring the text to your eyes and how to adjust the paper in relation to what article you were reading.
Your brain is excellent at planning what movements are going to take place and then adjusting for new situations that arise in real time.
However, the brains of autistic individuals were long thought to have problems in creating these internal models, or brain circuits, that predict motion. It was also believed that these individuals had difficulty in adapting to new situations, in which a new movement needed to be made quickly.
Researchers at the Kennedy Krieger Institute and Hopkins School of Medicine, led by Jennifer Gidley Larson, found that autistic children may not be any different from unaffected children in terms of these motor behaviors.
In an article recently published in Brain, this team of investigators found that any motor deficits seen in autistic children are probably not associated with an inability to predict motions.
Autism is a spectrum of disorders that is more commonly diagnosed in boys. The disorder involves social problems, language difficulties and motor deficits. While a lot of research has focused on the social side of autism, the authors of this research primarily considered which areas of the brain might be responsible for the motor deficits.
Children with autism can have problems riding a bike or using new tools, which are activities that are thought to be controlled by the cerebellum. The cerebellum is a structure in the back of the brain that is concerned with movement and coordination. When imaging or postmortem studies look at the brains of people with autism, the cerebellum is abnormal.
In order to test if autistic children had defects in forming predictive motor models, the researchers set up two experiments. The first experiment tested the children's ability to adapt to changing stimuli.
The children, both autistic and typically developing, were asked to throw a ball at a target. After several baseline trials, the children were given prism goggles, which distorted the visual information. Then, the participants were instructed to try to throw the ball at the same target.
This is a bit like trying to hit a target if you can only see it in a mirror - you cannot be entirely sure where the target really is. Your brain will have to integrate motor and visual cues to adjust your throw.
Both the control group and the autistic group had the greatest error in hitting the target when initially given the goggles. However, both groups were able to adapt, or change their internal motor programming to meet the new visual stimuli.
The second experiment involved learning how to use a new tool. In this case, both groups of children were asked to hold onto a robotic tool underneath a table. The individuals were unable to see the robotic arm, but were asked to use it in order to move a cursor towards a target on an LCD screen.
The robotic tool generated a force field in one task and exhibited rotation in another, which gave the children two situations in which to adapt their motor skills. The researchers did not find any significant differences between the two groups.
Since these two experiments are typically used to demonstrate use of internal motion modeling, the data suggests that autistic children do make use of this brain circuit. However, the cerebellum, which controls the internal models, is also abnormal in autistic children.
The investigators propose that other cerebellar functions may be hindered in people with autism, yet the functions of internal models and adaptation are essential and maintained. Once the brain circuitry involving autistic motor deficits is more completely understood, therapeutic approaches can be developed that can try to alter the children's behaviors.
