Sensory Processing in Autism
Everyone has to process sensory stimuli. That is how we can interact with the outside world. Parts of this are the eyes (seeing), ears (hearing), nose (smell), tongue (taste and feeling) and the skin (feeling, the sense of touch). Our senses give us information that we can then act on.
Our senses are connected to our brains via nerves, where the information comes in. Every second our brains receive an average of 11 million stimuli (bits per second). The first gate, where the stimuli enter, is the thalamus. You could see this as a regulator that determines which stimuli you consciously notice and which you do not. Of those 11 million stimuli, our brain could consciously process less than 0.001%, 100 bits. (The Sound Learning Centre, 2022)
You could compare the processing of the stimuli in autism with a drain that does not flow properly. Normally, 100 drops, 100 bits per second, fit in your sink. The drain can handle this and everything runs smoothly. Usually the tap is not open far enough to fill the sink, so there is no problem. In the case of autism, the tap is usually open a little further, so more water runs into the sink more quickly. If someone then has to deal with stimuli to which he or she is sensitive, that tap opens even further and the drain can no longer handle it, the container overflows and you have to deal with over-stimulation. Research shows that within the autism spectrum, women suffer and love sensory stimuli more during their lives than men. (Lai, et al., 2011) (Weiland, Polderman, Hoekstra, Smit, & Begeer, 2020)
Expectations and the Subconscious
The brain works a lot based on expectations. Everything you expect in a certain situation, such as trees in a forest, you do not consciously notice. You will notice a fence in the middle of the forest, your brain would not have placed that in the picture of fitting in the forest, so this deviates and ensures that that stimulus does reach your consciousness. This ensures that you can react quickly to deviations and not get distracted by everything you see. This also ensures that the brain spends less energy on processing all the stimuli that come in.
In autism, this filter appears to be more sensitive (and in some cases less sensitive) in many cases. You do not only notice the larger deviations such as a fence in the middle of the forest. You may also notice that the shape of that tree is different, that the bark looks different, or that moss is growing on that one tree. This ensures that you notice more details, but also that the brain spends more energy processing and placing all that information. “We see leaves and branches, where you see a tree. We see trees, where you just see a forest” writes Ernst Stuurman. (Stuurman, 2021, p. 14) Noticing more things therefore also means more stimuli that come through to your consciousness, those 100 bits are then full faster.
Over-stimulation by thoughts
So far, we have mainly discussed the processing of external stimuli. But the information that our brain receives about our posture, our balance, thoughts and feelings must also be processed. This leads to the fact that you could divide over-stimulation into 2 categories, two situations. Over-stimulation by information from outside, the senses, and over-stimulation by thought stimuli. (Leeuw, 2015)
Over-stimulation, a form of stress
Over-stimulation is actually a very strong form of stress. The stress is so strong that your body recognizes this as danger, the limbic-system comes into action, which leads to you going into survival mode. Your normal thinking blocks and you can only act primarily: fight, flight or freeze. In the case of over-stimulation, this often manifests itself in tantrums, crying spells or completely turning inward. Usually followed by complete exhaustion or other physical complaints such as headaches. (Leeuw, 2015) To think rationally during that over-stimulation, also known as meltdown, and to switch from fight to flight mode, for example, then takes a lot of effort.
That was it for today. Would you like to learn more about sensory processing in autisme or autism in general? Do let me know! For now, goodluck with the next steps on your bridge and I wish you all the happiness and an amazing rest of your day.
❤ Eva
Sources
The Sound Learning Centre. (2022, januari 7). Processing. Opgehaald van www.thesoundlearningcentre.co.uk: https://www.thesoundlearningcentre.co.uk/the-cause/processing
Lai, M.-C., Lombard, M. V., Pasco, G., Ruigrok, A. N., Wheelwright, S. J., Sadek, S. A., . . . Baron-Cohen, S. (2011). A Behavioral Comparison of Male and Female Adults with High Functioning Autism Spectrum Conditions. Autism Research Centre, Department of Psychiatry. Cambridge: University of Cambridge. Opgehaald van https://doi.org/10.1371/journal.pone.0020835
Weiland, R. F., Polderman, T. J., Hoekstra, R. A., Smit, D. J., & Begeer, S. (2020). The Dutch Sensory Perception Quotient-Short in adults with and without autism. Onderzoeksrapport, Vrije Universiteit Amsterdam; King’s College London; Academic Medical Center Amsterdam, Amsterdam. doi: 10.1177/1362361320942085
Stuurman, S. (2021). Autisme is geen puzzel: een bevrijdende kijk op buitengewone mensen (1 ed.). Hillegom: SAAM Uitgeverij.
Leeuw, B. d. (2015). Overprikkeling voorkomen : vaardigheden en technieken voor (jong)volwassenen met autisme (ASS) en/of ADHD. Amsterdam, Nederland: Uitgeverij SWP.