8/12/2009

ASD and Dyspraxia: What's the deal?

One fact that particularly interests me about ASD: it's often associated with dyspraxia. (According to LDOnline, "dyspraxia" means "a specific disorder in the area of motor skill development. People with dyspraxia have difficulty planning and completing intended fine motor tasks." I'm not sure why they only mention fine motor tasks; maybe these are more easily separable from problems based more in the body than the brain, or maybe they're just more severe).

For instance, Dr. Minshew found that many of the ASD kids in her study were dyspraxic. "The children with autism either had poor handwriting, or wrote very slowly. Many had difficulty tying their shoes and with using scissors."

Two studies investigated motor behavior and motor learning in ASD kids. Both studies interpreted their results as showing that children with ASD have less connectivity between brain regions overall. Furthermore, the greater the distance between regions, the less connectivity they have. (This suggests an abnormal, immature pattern of brain development. Normally, development strengthens connections between distant regions to create complex functional networks and weakens connections between neighboring regions to create more specialized, nuanced processing).

I find the results particularly interesting because I've known people who have similar motor behavior and motor learning to the ASD kids in these studies for most of my life, but have never been diagnosed with ASD, and lack a lot of the social and social language symptoms. I've usually interpreted these difficulties as problems with sensory processing and with sensory-motor connections (i.e., the ability to act on what one perceives). So as I examine the results, I ask: are these symptoms caused by developmental connectivity differences? Are they caused by sensory processing and sensorimotor differences? Are they caused by the first in ASD and the second in whatever weird agglomeration of issues these people seem to have? Are they caused by the first in some types of ASD and by the second in other types (since after all, ASD is a family of disorders)?

Motor Execution in High-Functioning ASD
For most people, tapping the fingers in sequence is the most natural thing in the world. We do it while typing or playing piano or a stringed instrument, and most of us do it when bored. But it isn't quite so simple for children with ASD. While neurotypical kids use the cerebellum, a "reptilian" brain region associated with automated motion, ASD kids rely more on the supplementary motor area, a region of the brain responsible for conscious, effortful movement.

“Tapping your fingers is a simple action, but it involves communication and coordination between several regions of the brain,” points out Dr. Stewart H. Mostofsky, the senior author of the study. Researchers compared the functional connectivity of the brain regions involved in motor planning and execution in typical and ASD kids. The children with ASD showed much less connectivity between these regions.

Mostofsky thinks that ASD kids are using the supplementary motor area in order to bypass their less-connected motor systems. He points out that the areas involved in motor tasks are fairly close together. Social and communication skills involve much more far-flung brain areas, coordinated in much more complex ways. So it's not surprising that kids with ASD would have weaknesses here.

As fascinating as the connectivity issue is, I'm more interested in the fact that ASD kids process consciously where most kids automate. This is true for social skills, too--what most people do automatically, they do by consciously following rules. (This is why there's a much higher correlation between IQ and social skills among ASD kids than there is among neurotypical ones. The study's at home, so citation will be added later).

This study looked at high-functioning ASD kids. Maybe the use of more-conscious areas is about more than just covering up weakness (poorly-connected lower areas). Maybe their more-conscious areas are actually a strength for them (relative to the norm), giving them an advantage in academic areas? Maybe people like Adam are excellent at social skills after the fact but not in the moment because their more-conscious processing takes too long to be helpful in the moment, but lets them use their cognitive strengths to understand what's going on later? Maybe, in other words, there's a strength explanation as well as a weakness explanation. Does the weakness cause the strength, as Mostofsky assumes, or does the strength cause the weakness (i.e., overreliance on strong brain areas causes the brain to invest less effort in developing others, thus causing a weakness to develop?)

Motor Learning in ASD
In another study in which Mostofsky was involved, researchers compared the movements of autistic and neurotypical kids as they learned to control a novel tool, and discovered that autistic kids seem to learn new actions differently than neurotypical ones.

"As compared to their typically developing peers, children with autism relied much more on their own internal sense of body position (proprioception), rather than visual information coming from the external world to learn new patterns of movement. Furthermore, researchers found that the greater the reliance on proprioception, the greater the child’s impairment in social skills, motor skills and imitation."

(It seems counterintuitive to me that proprioception should be associated with poorer motor skills, as we use proprioception to position our bodies and intuitively understand what a movement should "feel like.")

Researchers believe that, in opposition to the normal pattern of brain development, short-range connections between neighboring brain regions are overdeveloped and longer-distance connections are underdeveloped. Proprioceptive areas are close to motor areas, while visual-motor processing is father away. So kids with ASD use less-effective proprioceptive areas to guide their actions because their visual-motor and motor areas can't communicate effectively.

Notice, though, that the earlier study of motor behavior suggested that nearby areas with the same function were underdeveloped, not overdeveloped. Do we have a contradiction here, or is the pattern a little more nuanced than the articles report?

The researchers drew these conclusions because a lot of studies show abnormal connectivity in people with ASD. But it's also possible that these kids with ASD have poor visual-motor processing and are using proprioception to compensate.

How might this work?

As a child, Diana took violin, ballet, and tap lessons. At her violin lessons, she had trouble imitating her teacher's movements. She could succeed either when instructed verbally in detail or when the teacher physically moved her arms and hands into the proper position. Her mother (who observed her lessons) and I both believe that a visual processing problem was involved here. She had trouble sifting through the large amounts of visual data bombarding her to find the particular information she needed to copy a movement, which was why verbal instructions helped: they allowed her to focus on only the relevant visual details.

But verbal instructions only let her follow the teacher's instructions while he was present. They didn't give her feedback on the correctness of her movements when was practicing at home. Being moved into position, on the other hand, allowed her to feel exactly what she would feel every time she made the movement, allowing her to self-check-up. Thus, it was the most effective way for her to learn.

Ballet (ages 4-9 or 10) and tap (apx. ages 8-10) gave her more problems, which is why she eventually quit. When Diana danced freeform to "the music in her head," people remarked on her grace and expression, so she didn't have a problem with motor coordination per se. But when she actually tried to do what her teacher and classmates were doing in class, she would often do it backward, and she was a lot slower than they were. Diana could answer correctly if you asked her which was her right and which was her left, but when she actually had to move, mirrors confused her, and she'd move left while everyone else was moving right (and vice versa). She didn't have that proprioceptive input--the teacher moving her body into position--and she didn't get individualized verbal input, so she never really figured out what she was doing.

Sounds a lot like visual processing problems and specifically visual-motor coordination problems, plus issues with mirror reversals, doesn't it?

Where Does This Leave Us?

These 2 studies raise the following questions:
  1. Why do so many people with ASD experience dyspraxia?
  2. Where does someone like Diana, a person without ASD but with dyspraxia, fit into this?
The answers remain unresolved. But to recap, here are some options:
  1. Dyspraxia in ASD is caused by abnormal connectivity patterns.
  2. Dyspraxia in ASD is caused by areas of strength creating areas of weakness.
  3. Dyspraxia in ASD is caused by visual-processing and specific visual-motor coordination problems.
  4. There are at least 3 types of ASD with dyspraxia, caused by abnormal connectivity patterns; areas of strength creating areas of weakness; and visual-processing & visual-motor problems, respectively.
  5. People with ASD and people without ASD can have dyspraxia for different ones of these reasons. For instance, people with ASD might have dyspraxia caused by abnormal connectivity and/or areas of strength creating areas of weakness, while people without ASD could have dyspraxia caused by visual-processing & visual-motor problems (and maybe also areas of strength creating areas of weakness).
  6. People with ASD and people without ASD can have dyspraxia for the same reasons. It's not a symptom of ASD that's also an independent disorder. It's an independent disorder that just happens to coexist with ASD a lot (maybe because they're caused by problems with the same gene).