The Physiology Behind Autism

An autism spectrum disorder is defined by the DSM-5 as a deficit in social communication and social interaction across multiple contexts. People with Autism regularly show restricted repetitive behavioral patterns, regularly experience over hyperreactivity to environmental stimuli, and usually experience problems in developing, maintaining, and understanding the dynamics of personal and social relationships (AutismSpeaks). For a person to be diagnosed with Autism, symptoms of the disorder are usually present in the early developmental period of infancy and childhood. However, symptoms of Autism may not become fully manifest until the person is presented with complex social constructs or sensory stimuli which may trigger hyperactivity. A person with Autism will usually experience significant impairment in social and occupational constructs. While intellectual disability and autism spectrum disorder frequently co-occur, autistic individuals may exhibit levels of common or higher intellect. Deficits in social communication for an autistic individual, however, are normally lower than expected for the general developmental curve of the neurotypical population. While individuals with Autism spectrum disorder may exhibit different levels of intelligence, social reciprocation, and accommodation to environmental stimuli, there are certain characteristics of the brain’s physiology that are common in individuals with Autism. These characteristics are a surplus of synapses between brain cells, overcompensation of certain areas of the brain towards environmental stimuli or sensory overloads, and cognitive difficulties with synchronizing multiple regional brain functions together (Hamilton, 2012). These points will be further explored throughout this essay. 

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Concerning the level of synapses between brain cells in a person with Autism, research across multiple fields of neuroscience has shown that individuals with Autism are likely to have a higher level of brain connections that standard neurotypicals. Among the many genetic mutations that occur which are linked to autism, there are six genes that attach a molecular tag, called ubiquitin, to proteins. These genes, called ubiquitin ligases, function as a coding, telling the rest of the cell bodies how to deal with the tagged proteins (Pamela Valnegri, et al., 2017). People with autism may carry a mutation in the RNF8 protein that prevents one of their ubiquitin genes from working properly. However, until very recently, the problems with how tagging proteins affect the brain’s hardwiring and operations, and why such problems may lead to autism, have remained poorly understood by scientists and doctors in the field of neuroscience alike. In the study conducted by the Washington University School of Medicine, Dr. Pamela Valnegri (the head researcher) and her colleagues removed the ubiquitin gene RNF8 in neurons in the cerebellum of young mice to see whether the mice would develop more brain synapses than normal. The results of the research performed indicated that neurons within the central and peripheral nervous systems that lacked the RNF8 protein formed about 50 percent more synapses, connections that allow neurons to send messages from one cell body to another, than those with the RNF8 gene still intact. By measuring electrical signals in the receiving cells, the researchers at the school of Medicine found that the strength of the electrical signals fired among the neurons was doubled in the mice that lacked the RNF8 protein. When the researchers tested the ability of the mice to learn motor skills and participate in a task involving high amounts of environmental stimuli, the mice without the RNF8 gene consistently performed lower in the assignments that were given to them than the mice with the RNF8 gene still intact. The findings of this research may express why individuals with autism tend to perform poorly a task that involves complex motor movements and/or high amounts of environmental stimuli. With the increase of synapses within brain regions, an individual with Autism experiences a higher sensitivity to the stimuli found within their environment. Certain types of environmental stimuli may be either distracting or irritating to a person with autism. Without the ability to filler out peripheral environmental stimuli, a person with autism will experience difficulties in learning complex motor behaviors or experience sensory meltdowns due to overloads in their cognitive processes.

In situations in where a person with autism experiences a sensory overload, the brain many overcompensate in certain areas. This overcompensation performed may exhibit itself as a meltdown, which may manifest itself in various ways. Some people with autism who experience a meltdown may exhibit signs of distress. Others may become violent, while other individuals with autism may show a loss of self-control. A meltdown for a person with autism is fundamentality different for a temper tantrum. In a tantrum, behaviors arise from emotional escalation and conscious choices. Yet, meltdowns for someone on the autism spectrum disorder are part of a neurological shutdown that short-circuits a person’s ability to reason or self-regulate themselves. In a meltdown, under the stress of sensory overload, the brain’s limbic system activates the fight or flight response. The amygdala, in this fear state, triggers a flood of stress hormones and chemicals (adrenaline, norepinephrine, cortisol). From this influx of chemicals, the sensory processors in the caudal regions of the brain in communication with the neural circuits of frontal cortex reach a point in where the brain experiences a sensory overload. This sensory overload includes a shutdown of the synaptic ventricles of the prefrontal cortex and inhibits the brain’s higher level executive cognitive functions (Day, 2017).  For an autistic individual experiencing a meltdown, functions such as higher-level reasoning patterns, problem-solving, and self-regulation become inactivated at this time. The meltdown experienced by an individual with autism usually manifested itself in one of two different responses. The first response towards a sensory overload may exhibit itself in an autistic person as a physical outburst, in where the individual with autism may become violent or express strong negative emotions. The second response towards a meltdown for a person with autism may be a withdrawal, with a general lack of responsiveness or reciprocation towards the outside world. This may manifest itself as either curling up, placing the hands over the ears or eyes, or murmuring or humming to dull the sensory experiences that they are bringing in. 

When a meltdown occurs in an individual with autism, it usually arises from cognitive difficulties with synchronizing environmental stimuli over multiple areas of the brain. In the brain of a person with autism, most studies suggest that people with autism experience hypo-connectivity in different regions of the brain during performance of certain functions such as examining language patterns, processing emotional stimuli, visuomotor coordination, working memory, and processing cognitive executive functions (Ha, et al. 2015). The areas which receive the greatest strain when processing these higher-level tasks tend to be the areas of the frontal cortex, the language centers (Broca’s area and Wernicke’s area), and the main sensory areas of the brain (primary auditory cortex, primary, somatosensory cortex, and primary visual cortex). Often, when trying to perform a higher-level task, a person with autism will likely focus intensely on one area of the task to complete before moving on to the next step that needs to be performed. This process can also be seen within the brain. For a person with autism, the brain tends to focus upon one area of task at a time. Once the input stimuli from the environment is processed in a region, instead of concentrating all parts of the brain to receive the encoded message, an individual with autism will likely receive a much stronger message in the certain areas they choose to intensely concentrate on, while the other parts of the brain may necessary to the completion of the task may receive a light signal on what to do at that moment. This can make tasks that involve high amounts of concentration or task that require multiple regions of the brain to be concentrated very challenging for a person with autism. As people with autism prefer to break down a task and process one item at a time, they may become overwhelmed when they are in an environment with too many outside stimuli or are asked to perform a task with too many higher cognitive variables. Individuals with autism may also become frustrated when asked to perform a complex task in a short amount of time as their sensory processing centers may not be able to process all the aspects of a task in a confined time length.

The physiology behind the autistic mindset may bring challenges that neurotypicals may not face or relate to. Individuals with autism regularly experience challenges with social communication, sensory overload, overcompensation, and other aspects which create obstacles in their daily lives. Yet, early intervention and therapy can play a major role in helping a person with autism in the struggles and challenges they experience. As every individual with autism will range in areas of intelligence, personality, and how sensitive they are to environmental stimuli, not all therapies typically suggested may be appropriate. Autism is also heavily tied to the brain’s physiology. Some task, no matter how many times attempted, may not be able to be performed with autistic individuals on the lower ends of the spectrum. This is not that the individual with autism is not trying to perform the task, but that they may not have the cognitive ability or resources due to the way their brain has developed. Yet, even individuals on the lower ends of the spectrum are still people who are able to show love, affection, and emotion. By understanding the challenges an autistic person experiences, and the way the brain of a person with autism functions, family members and loved ones of the autistic individual may be better able to relate and aid them. By providing proper support and affection, family members and friends may help a person with autism find more fulfillment within their daily lives and help them overcome some of the obstacles associated with autism.

References:

• AutismSpeaks. (n.d.). DSM-5 Criteria. Retrieved December 8, 2018, from https://www.autismspeaks.org/dsm-5-criteria
• Day, N. (2017, August 30). Executive Functions: What They Are, and Exercises to Strengthen Them · Raising an Extraordinary Person. Retrieved December 8, 2018, from https://hes-extraordinary.com/executive-functions
• Ha, S., Sohn, I., Kim, N., Jeong Sim, H., & Cheon, K. (2015, December 16). Characteristics of Brains in Autism Spectrum Disorder: Structure, Function, and Connectivity across the Lifespan. Retrieved December 8, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4688328/
• Hamilton, J. (2012, June 04). What’s Different About the Brains of People with Autism? Retrieved December 8, 2018, from https://www.npr.org/sections/health-shots/2012/06/04/154175007/whats-different-about-the-brains-of-people-with-autism
• Pamela Valnegri, Ju Huang, Tomoko Yamada, Yue Yang, Luis A. Mejia, Ha Y. Cho, Anna Oldenborg, Azad Bonni. RNF8/UBC13 ubiquitin signaling suppresses synapse formation in the mammalian brain. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01333-6, https://www.nature.com/articles/s41467-017-01333-6