Can you imagine being in a situation where there is so much stimulation, somewhere like your eyes, ears, or skin, that causes an overload of neurological impulses to the brain that makes you want to shut down? Sometimes we are in a place that has too much going on that we have to take a step back and regroup because it is clouding our brain with too much information. Well for some children with autism, this is a regular occurrence in normal activities. Now it has been shown that children who have autism having larger brains. When the brain is developing, children go through a pruning process that gets rid of unimportant dendrites in the brain so it frees up space for the important things to make more connections and become stronger. This pruning doesn't occur in this instance and there are many neurons with not as strong of connections between them.
During what people call the critical period of development, your brain is like a sponge, absorbing all new information easily. The specific nerve growth factor brain-derived neurotrophic factor (BDNF) is a chemical that plays a large role in reinforcing plastic change during the critical period. It also increases the speed of which electrical signals are being transmitted. BDNF turns on the nucleus basalis, which allows us to focus our attention and remember the stuff you are learning. Not only does it help you to learn new information easily, it also shuts down the critical period, because the brain needs some stability and isn't effortlessly plastic at all times. This is why we must be learning something that surprises us or particularly interests us or is important, because it activates the nucleus basalis which helps us to pay specific attention and store that information in our brain. Now back to autism, neuroplastician Michael Merzenich's theory of why there is no pruning and overstimulation and oversensitivity occurs is because of a premature release of BDNF. He thinks that there is a gene that predisposes children to have this premature release of the chemical that opens and closes the critical period, so that instead of important connections being reinforced, all connections are reinforced, which skips the pruning process, and since BDNF also closes the critical period, it closes earlier with many connections that are disconnected. This means that if say a child has sensitivity to auditory stimulation, if they hear one frequency, the whole auditory cortex starts firing because connections were never strengthened and therefore causes confusion in the brain when all neurons are firing at once.
So if a child has a melt down in a place that has a loud area, doesn't look you in the eye, or can't stand certain fabrics on your skin, they are not necessarily doing it on purpose. The brain is overexcited from the stimulation and cannot handle all of the stimulation at once. The brain is meant to strengthen connections that are important so we can use those repeatedly and the messages start to travel faster, which is why we end up having habits (good and bad) and can do things on autopilot (like drive to our house or place of work without consciously thinking about every turn), but when it is not allowed to strengthen the important ones and keep the unimportant ones weakened, the brain cannot differentiate and takes in all information because it thinks it's important. Remember this if you're ever around people with autism - everyone would become frustrated if their brain overly fired signals that made for chaos in the brain - so relax, and help them to relax too.
