SEARCHING THE BRAIN FOR CLUES IN AUTISM


Discovering a "release mechanism" like Parkinson's disease in autism :

Dr. Edward R. Ritvo along with his team designed a study to test their idea that the rhythmic hand flapping seen so often in autistic kids was due to brain dysfunction, and was not just an emotional release, which was the accepted view at the time. It was generally thought at that time to be simply an expression of emotional distress, a form of learned behavior that could be 'unlearned' by conditioning.

They figured that if repetitive hand flapping was voluntary and due to emotional distress the speed of the flapping would change as the child become more or less emotional(frustrated, angry or whatever) and that different kids would flap at different speeds. On the other hand (pardon the pun), if it was driven by abnormal brain function, then all autistic kids should flap at about the same speed. Also, once they start they should not speed up and slow down. They should start at cruising speed, and stay there till they stopped. This is the case with hand tremors in Parkinson's disease. In this neurological disease all patients flap at about the same speed and start and maintain that speed till they stop.

Dr. Edward and his teammates after taking permission from children's parents took movies of large number of autistic kids who were "frequent hand flappers". Finally they played the movies back at slow speed and counted the number of flaps per minute.

They discovered to their delight, that their idea was correct. All the kids they filmed flapped at about the same speed, and started and kept it steady till they stopped. Similar high-speed movies of many autistic kids in other cities around the country were also taken. Wherever they came from, they flapped at the same speed, and maintained the same speed while they were flapping.

There was no relationship between how the kids felt (happy, sad or angry) and the speed of their flapping. These results helped them debunk the theory that flapping was emotionally driven, caused by psychological poisoning from bad parents, or just learned. They provide another step on the road to "proving" that abnormal brain development was the culprit causing autism.

Discovering developmental delays in the balance system :

During their observational studies  Dr. Edward and his team were struck by how many autistic kids spent hours spinning, twirling, and swinging without getting dizzy. This caught their attention as it could indicate a problem in the part of the brain that adjusts the sensitivity to vestibular (inner ear) stimulation.

 

They tested the vestibular system by spinning a patient around in a special chair with a ring around it. After a set number of spins they stopped the chair suddenly by grabbing the ring. Then they timed how long the subject's eyes moved rapidly back and forth with a stopwatch. This gives an objective measure of dizziness. This eye movement after spinning stops are called 'post-rotator nystagmus'.

Although the chair had a ring around it, they did not trust the autistic kids to sit in it alone, so they modified the experiment by having them sit on their (non-autistic) parent's laps. After spinning them to the right, they stopped the chair quickly and timed their dizzy response. Then they did the same thing to the left. Finally they repeated all the spins in the dark while they measured the duration of their eye movements electronically.

To their surprise, they noted right off the bat that they had a lot of dizzy parents, but the autistic kids were calm as contented clams as soon as the chair stopped. Their stopwatch proved that autistic kids had significantly decreased responses to spinning when the lights were on. However even more surprising, in the dark both groups had longer responses but there was no longer any difference between them.

How to explain this unexpected and perplexing discovery?

They were able to ascertain that the difference was not age related.  Dr. Edwards best guess was and still is that the part of the brain that co-ordinates the two different sensations. Vision and spinning, is not fully developed in the autistic kids. But in the dark, with only one sensation to handle, spinning, the brain of the autistic child functions just as well as the non-autistic brain.

Here was subtle but definitive evidence of brain dysfunction in the system that turns up and down the volume, or adjust our sensitivity to sensations. The term used to describe this phenomenon is called "perceptual inconstancy".

The results of the vestibular experiments certainly point a way to understanding how the brain can dampen a response when two sensory sensations come in together, and yet respond normally when one comes in alone.

Author

Dr. Ajay Bhardhwaj

Fellow in Developmental Pediatrics

Centre for Child Development and Disabilities