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On 28 May, I attended the first online webinar in the 2020 Autism Expert Series offered by the Autism Resource Centre Learning Academy. This webinar was titled ‘Are Sensory Issues in Autism Sensory? Autism, The Predictive Mind and Sensory Processing’ and was presented by Dr Peter Vermeulen. This insightful presentation challenged conventional beliefs about hyperreactivity among individuals on the spectrum as well as effective ways of addressing sensory issues.
What is hyperreactivity?
Dr Peter Vermeulen began by acknowledging that many individuals on the spectrum experience sensory overload and discomfort, otherwise known as hyperreactivity. The conventional explanation is that autistic individuals are hypersensitive to stimuli, and the suggested intervention is thus to reduce or eliminate stimuli. For instance, individuals who are hyperreactive to noise may use noise-cancelling headphones, and some places like cinemas and supermarkets may have quiet hours or quiet areas. However, Dr Peter Vermeulen cautioned that there may be other possible reasons for sensory issues. He highlighted the importance of finding out the real cause of sensory issues in order to provide the right intervention.
Dr Peter Vermeulen explained that there is a difference between sensitivity and reactivity. The former refers to a physiological response with a sensory threshold, which is associated with the sensory system in the brain. On the other hand, the latter refers to a psychoemotional or behavioural response, which is associated with the limbic system in the brain. He shared that the literature review indicates that there is no clear evidence of any difference in sensitivity or sensory thresholds between neurotypical and autistic brains. Rather, there is only evidence of difference in reactivity. In fact, the DSM-5 mentions the term ‘reactivity’ instead of ‘sensitivity’. Therefore, he suggested that we should consider sensory issues as a problem of psychoemotional response rather than having a sensory base, and accordingly, interventions should focus on the limbic rather than sensory system.
What is the predictive mind?
Dr Peter Vermeulen proceeded to share some misconceptions about the brain. Traditional models of the brain state that the feedforward process is bottom-up, from stimulus to processing to meaning, while the feedback process is top-down. However, more recent research indicates that this model should be flipped; the feedforward process is top-down, from prediction to checking prediction to stimulus, while the feedback process is bottom-up. Moreover, the input coming from the senses are unreliable. The brain does not process stimuli. Instead, the brain processes what is different from the stimuli it predicted. This explains why hyperreactive individuals on the spectrum may cover their ears in response to sudden loud noises by others, but appear unaffected by the loud noises that they themselves produce. An interesting analogy that Dr Peter Vermeulen gave was that we cannot tickle ourselves, because we initiate the stimulus ourselves and thus there is no prediction error.
Prediction error = Predicted stimulus - Actual stimulus.
Individuals on the spectrum make precise, inflexible predictions about the sensory environment, and do not adapt these predictions based on context. They treat sensory information as being more informative when estimating the state of the environment. This is also known as the HIPPEA (‘high inflexible precision of prediction errors in autism’) hypothesis. Furthermore, how much weight you give to a prediction error depends on the certainty about your model of the world and the predictions based on that model. Dr Peter Vermeulen speculated that uncertainty and anxiety leads to increased alertness, which in turn results in high precision in expected prediction error, which in turn results in small deviations from predictions being noticed and processed, which in turn results in hyperreactivity. In other words, sensory issues may actually be due to uncertainty and anxiety.
How can interventions take into account the predictability factor in sensory issues?
As mentioned earlier, Prediction error = Predicted stimulus - Actual stimulus. This means that sensory interventions involve two approaches; not only manipulating the actual stimulus, but also manipulating the predicted stimulus. Indeed, current sensory interventions mainly involve taking away or reducing the stimulus, yet long-term sensory deprivation can potentially be harmful. Hence, Dr Peter Vermeulen proposed that we should help individuals on the spectrum make better contextualised predictions regarding the sensory environment. For example, social stories can include more sentences describing and explaining the sensory environment, such as explaining that a party may have loud noise as the children are excited and competing to be heard. We should also give individuals on the spectrum a sense of control over stimuli. For example, social stories can include strategies that individuals on the spectrum can use, such as letting them know they have the option of using earplugs or leaving the room if the noise gets stressful.
Lastly, Dr Peter Vermeulen noted that while the current literature and his webinar tend to focus on hyperreactivity, we should not ignore hyporeactivity. For instance, individuals with hyporeactivity may show decreased responsivity to pain, reduced detection of temperature, reduced odour detection, and poorer identification of flavours. These are potentially dangerous, with implications for health and medical issues. In particular, Dr Peter Vermeulen noted that individuals on the spectrum may have difficulties understanding sensory experiences in the body, otherwise known as interoception. They may lack awareness regarding one’s cardiac activity, hunger, thirst, pain, and the need to make bowel or bladder movements. Dr Peter Vermeulen postulated that hyporeactive autistic individuals have not learned to read their own body, and he recommended Kelly Mahler's The Interoception Curriculum as a way of teaching individuals with autism to recognise inner body signals.
All in all, my main takeaway was that sensory issues in autism may be reactive rather than sensory. Specifically, hyperreactivity may stem from uncertainty and greater weight given to prediction errors. We can empower individuals on the spectrum by giving them information about the sensory environment beforehand to make things more predictable, as well as giving them a sense of control over the sensory environment by teaching coping strategies. In addition, while the discourse tends to revolve around hyperreaactivity and the external environment, we should not neglect hyporeactivity and the internal environment. Social stories should be designed with these concepts in mind.
All blogposts on 2020 Autism Expert Series:
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