By Shulamite Green, PhD
University of California, Los Angeles
Semel Institute for Neuroscience and Human Behavior
Ahmanson Lovelace Brain Mapping Center
Until recently, sensory features were overlooked by the research world compared to the social and communication aspects of autism, but individuals on the autism spectrum and their families have been observing these sensory differences and related challenges for a very long time. I was first introduced to sensory over-responsivity in 2005, through the incredibly compelling account of Dr. Temple Grandin, an autistic individual. In Dr. Grandin’s book, “Thinking in Pictures,” she describes the overwhelming feelings of sensory overload that she experienced as a child, including withdrawing from touch, as well as fear and pain responses caused by certain loud or unexpected noises. By her description, this sensory over-responsivity was one of the primary challenges she faced as a child, and played a key role in disconnecting her from the social world. Though her book was written in 1995, even a decade later, the prevailing view of autism was still of a condition that was primarily social in nature, and it was commonly believed that many autistic individuals were not interested in social interaction. Dr. Grandin’s account that her sensory experiences were so profoundly different, often causing her to be socially disengaged, was fascinating to me. There seemed to be a large disconnect between autistic individuals and their families, who commonly reported or observed these sensory differences and challenges, and the research world, which was almost exclusively focused on social skills and language. It was clear to me from working with individuals on the autism spectrum that these different sensory experiences were important features of autism, but at the time, there was very little research on what caused these differences or how to treat them. This is a big piece of what motivated me to study why and how certain brains responded differently to sensory information.
Recent imaging research has helped us better understand how the brain processes sensory information in autism. For example, in our studies we use functional magnetic resonance imaging (fMRI), a non-invasive method of examining blood flow changes in the brain, to see how the brains of children with and without autism respond to aversive sensory stimuli. This research has shown that brains of children with sensory over-responsivity do indeed respond differently in a number of ways – for example, they show greater responses in the amygdala, a region of the brain important to processing threat and directing attention to important aspects of our environment. This can help explain why individuals like Dr. Grandin experience elevated anxiety and fear in response to unpleasant sensory sensations. We also see that the brains of children with sensory over-responsivity habituate less quickly to sensory information. This means that background sensations that most of us “tune out” over time like the sound of a clock ticking or the feeling of the clothes on our body might continue to be processed by individuals with sensory over-responsivity. Most of us filter out extraneous or ongoing sounds and tactile sensations, allowing us to focus on new or important sensations. If the brain continued to process all incoming sensations, this could certainly lead to the feeling of overwhelm and sensory overload reported by many autistic individuals. The thalamus is another a brain region that likely plays a role in this sensory overload – the thalamus routes sensory information to the correct area of the cortex for processing and filters out less important information. Consistent with that, we see that the thalamus does not modulate changes in incoming sensory information as much in autistic individuals, meaning that it may not adapt as easily or flexibly to changes in the sensory inputs coming into the brain. Finally, we have found that some autistic individuals who have less difficulty with sensory over-responsivity show a pattern of brain connectivity associated with more regulation during aversive sensory processing. This pattern, which shows the prefrontal cortex being more functionally connected with the amygdala, is often related to emotional or behavioral regulation, such as reducing anxiety or anger. This suggests that a subset of autistic individuals may use the prefrontal cortex to help cope with the overwhelming sensory sensations and reduce their feelings of anxiety or overwhelm.
The next steps are to understand how these brain insights can help us create more intervention options for sensory over-responsivity. Currently, occupational therapists (OTs) are the professionals with the most experience assessing and treating sensory challenges, and an OT consult is recommended for any individuals with sensory differences that are impacting their day-to-day life. OTs take a practical approach of considering which daily life functions are affected and working through coping strategies for how to make these situations easier. However, there is still a great need for research-based interventions that target the causes and underlying biology of sensory over-responsivity. Insights from the brain suggest, for example, that exposure treatments, in which individuals are gradually exposed to higher and higher levels of the sensory stimulus, might not be effective – if the brain continues to process incoming stimuli rather than tuning it out, even after a prolonged period of time. Further, even if one were to get used to one stimulus such as a vacuum cleaner, research suggests that this might not generalize to other environmental sounds, and it will be very difficult (and unpleasant) to conduct exposure therapy on every possible noise. Rather, evidence that prefrontal cortex regulation of the amygdala is related to reduced sensory over-responsivity in some individuals suggests that coping mechanisms that can increase such regulation may be helpful. Existing cognitive-behavioral therapy (CBT) has already been successfully modified for treating anxiety with individuals on the autism spectrum and could potentially be adapted for use with sensory coping as well. Some of our current brain imaging research aims to examine potential sensory regulation techniques to see if these can help engage prefrontal cortex and bring down amygdala responses. However, such prefrontal cortical engagement is usually effortful, at least at first, and interventions that can bring down the initial arousal and anxiety without the need to cope might be even more effective for some individuals. Therefore, another approach includes examining whether a beta-blocker often used for anxiety can reduce uncomfortable arousal during sensory sensations. Overall, our goal is to use what we know about the brain to create interventions that will reduce the painful experiences of sensory overload and make day-to-day life easier for individuals on the autism spectrum.
For more information about our current work, or for information about how to participate, please visit our Sensory, Cognitive, and Affective Neurodevelopment (SCAN) Lab website: https://scanlab.dgsom.ucla.edu/ or contact us at firstname.lastname@example.org. We currently have participation opportunities for autistic and typically developing children and adolescents ages 8-15 as well as autistic individuals with sensory over-responsivity ages 8-35 years.
About Shulamite Green
Dr. Shulamite Green is an Assistant Professor in the Department of Psychiatry and Biobehavioral Sciences at UCLA’s Semel Institute. Dr. Green received her doctoral degree in clinical psychology at UCLA in 2014. Thereafter, she completed a postdoctoral fellowship at the UCLA Semel Institute with a focus on pediatric neuroimaging. Dr. Green’s research is focused on the neurobiological bases of sensory over-responsivity, a common and impairing condition in which individuals over-react to sensory stimuli in their environments, causing challenges with participation in school, work, family life, and the community. Dr. Green conducted some of the first fMRI work demonstrating brain differences in children with autism spectrum disorders (ASD) specifically related to sensory over-responsivity, as well as identifying potential brain mechanisms through which some children with ASD regulate their sensory responses. She has continued to build on this work to identify how certain brain areas contribute to or regulate these difficulties and interfere with or facilitate attention and social functioning.
Dr. Green’s work has been funded by multiple grants from the National Institute of Mental Health as well as the Simons Foundation for Autism Research, the Eagles Autism Foundation, and the Brain and Behavioral Research Foundation. Dr. Green received the International Society for Autism Research Dissertation Award as well as their Slifka/Ritvo Award for Innovation in Autism Research. She was also recently awarded a NARSAD Young Investigator Award. Clinically, Dr. Green serves as the autism consultant for UCLA TIES for Families, a program that provides extensive inter-disciplinary services for families adopting children from foster care. Dr. Green conducts autism evaluations and consultations for therapists working with families in this program.