Sensory Processing and Long-Term Memory - Allie Dennis

The senses are important to our everyday experience in life. Picture sitting under a nice maple tree in a local park, smelling the leaves of Autumn, turning the page of a good book, and visualizing the scene from your favorite story just by reading the words on a page. This is a favorite memory of mine, but maybe for you it’s going to the beach, feeling the sand between your toes, smelling the salty ocean breeze with a cooling beverage and magazine. Either way, you need all five senses to fully enjoy the moment.

What happens if your phone buzzes or a cute but leashless puppy runs onto your favorite moment? All your attention goes to that distraction, and most likely, you're able to recover from that and go back to what you’re doing. Although not everyone can easily shift from one distraction to another, sensory processing has a lot to do with this.

Why do the senses matter?

The five senses and your brain are always taking in information, whether you realize it or not. The only difference in being able to recognize it is that you are actively engaging with that sense in the present moment, storing it into short-term memory, and with enough attention, potentially to long-term memory for you to recognize in the future.

What is long-term memory?

Long-term memory has specific parts, including explicit memory, where you can consciously recall information like special events and the details of a scene, who was there, what was happening, and why. An explicit memory most people have is a special birthday party or graduation of some sort.

Semantic memory is the memorization of facts such as your name, address, and the year you graduated from high school. Maybe you even remember that fact from your last high school test. If it was important enough for you to remember or you’ve used that fact often, most likely it’s still in your semantic memory.

Implicit memory is a part of long-term memory that does not necessarily require our full attention to be encoded into long-term memory. This memory can be described as procedural memory, such as learning to complete a task like washing the dishes. This task you’ve done over and over with different results and have changed your approach as you go. You may not have the specific language to describe the day you learned to wash the dishes, but you know how to do it.

Visual memory and the brain

Visual memory has its own region in the brain, and we have short-term memory specifically for what we see and give our attention to. In fact, the visual system is the first sense to develop in infants, and that is pivotal to their development, along with the auditory system. The visual system develops gradually within the first two years of life, with many milestones children should hit to develop motor control skills, depth perception, and social engagement skills (Thye et al, 2018).

Think about whether you have a baby who has trouble with visual attention and whose eyes won’t focus by 8 months. They may have trouble walking because they can’t reach the next developmental stage of motor development without the ability to focus their gaze. This would be considered a physical impairment that can affect cognition and development if not addressed by a pediatric eye specialist.

In other words, the visual short-term memory lasts 10-20 seconds after seeing a scene, and if encoded in the brain, it will go to long-term memory for access later. The baby that can’t focus and shifts their eyes away from targets without control may not have enough motor control to encode into long-term memory.

Visual short-term and long-term memory in neurodivergence

Abnormal visual patterns have been found in some studies and are considered an indicator of an early autism diagnosis. Some of the patterns observed in autistic individuals include aimless visual exploration, lack of visual fixation for social engagement, and difficulty diverting attention. Some studies suggest that there is an upregulation of excitatory neurons in the visual short-term brain areas and downregulation of GABA neurons, indicating a neurochemical component to visual concerns in Autism (Stevenson et al. 2021).

In a study comparing Autism participants and participants without a diagnosis of Autism, it was indicated that low-level sensory information was prioritized over high-level sensory information in the Autism participants. Low-level sensory information includes the shade of color on screen and where it is placed. High-level sensory information is the precise location once the screen is changed to another slide. In this study, Autism participants had binding errors or lacked long-term memory for precise locations on a screen (Stevenson et al. 2021).

Attentional awareness is considered to be an important aspect of long-term memory encoding. Long-term memory deficits in Autism have been shown to include episodic memory concerns but not implicit or semantic memory. The results of this study seem to indicate that there is still much more research to be done to understand why episodic memory is affected but not other forms of long-term memory (Stevenson et al. 2021). Additionally, there have been studies on Autistic adults that showed comparable results to older adults in episodic memory, although some outperformed older adults . This variance could be due to episodic memory and context memory skills that some autistic adults learn throughout their lives (Justus et.al, 2021).

Auditory processing in neurodivergence

Research has also shown that auditory processing, specifically filtering, can impact behavioral responses in children as early as 3 years of age, lasting until 9 years of age, regardless of intelligence. Difficulty with auditory processing at 3 years of age showed up as increased disruptive behaviors, agitation, and hyperactivity, and can improve with community-based interventions that target the items on the Auditory Filtering subset. The subset is a range of tests, including objective measures to understand the child's ability to filter out background noise and process speech noise (Lau et al., 2023).

Somatosensory processing

Sensory seeking behaviors and sensory avoiding behaviors are commonly known in the neurodivergent community. Although there is much more complexity to why someone with an Autism diagnosis might have a combination of both. There are many factors in sensory seeking and avoidance that are common in ADHD, Fragile X syndrome, and cerebral palsy, but this does not necessarily mean someone with Autism has these diagnoses (Casio, 2010).

Some research points to tactile defensiveness or a hyperactive and/or aversive response to tactile stimuli as an indicator of early ASD diagnosis. Eating behaviors that are picky and aversive to texture have also been observed in the early diagnosis of ASD. Sleep and behavior problems are more likely to occur if the child is tactile defensive to stimuli that would be considered not a concern by neurotypical individuals, like clothing texture or the temperature of the room. Somatosensory seeking can present as children seeking stimulation from outside sources through deep pressure, hugging, or repetitive touching and eating of objects that are not food, as well as head banging (Casio, 2010).

Brain scans of adults with Autism spectrum disorder with somatosensory processing concerns have revealed that there may be an enhanced tactile perception in Autism, but not an appropriate adapting response through cortical inhibition. Body representation in the brain studied through brain scans on Autistic adults showed additional organizational concerns of the body's representation in the somatosensory cortex, indicating a top-down dysregulation in the prefrontal cortex (Casio, 2010).

Additional research is needed to understand exactly how the brain in childhood becomes disorganized in the somatosensory cortex. For now, diagnoses include parent observational reports, clinical observations, and psychophysical experiments. Interventions can include one play therapy session directed by the child using sensory integration therapy for hypersensivity and hyposensivity. In this therapy, a clinician builds on behavioral skills, developmental, and cognitive levels of the child to increase the capacity of the child's tactile, vestibular, and proprioceptive systems. Auditory and visual systems must be developed appropriately for this intervention to have the maximum benefits for the child.

What does this all mean for long-term memory?

Long-term memory acquisition requires top-down processing, and Autistic individuals' sensory differences, visual, and auditory differences can make it difficult to develop long-term memories. Long-term memories are important for the integration of social and behavioral skills that will assist someone in navigating our society, and this can present challenges to neurodivergent individuals (healthychildren, 2019).

Skill-based interventions from a bottom-up approach may be helpful for some individuals on the spectrum. This can include body-based interventions to calm the nervous system, play-based therapy, and skill development with special interests, including cognitively appropriate challenges.

My personal story on sensory needs and the developing brain

Sitting reading a book in a park is a special interest of mine. I enjoy listening to silence, but I can be overwhelmed with sensations that are unavoidable, like a cute dog running up on me and trying to say hello. A bottom-up approach to helping me with the unexpected can include taking my time to look at the dog, look around for its owner, breathe, and find a way to decide what to do next.

At times, this may look like calling for help from a trusted friend and having someone to walk me through some options due to overstimulation. Other times, I can handle the friendly dog and have a nice conversation with their owner. My long-term memory may be off temporarily, or it is on, and I remember how I’ve responded in the past.

This will not look the same for another person who is practicing bottom-up processing, and it does take time for the brain and body to remember how to respond to unknowns or new material. Developing an understanding that the brain is able to learn regardless of neurodevelopmental and sensory challenges is important to be your own or someone else’s advocate.

References

Cascio, C. J. (2010). Somatosensory processing in neurodevelopmental disorders. Journal of Neurodevelopmental Disorders, 2(2), 62–69. https://doi.org/10.1007/

s11689-010-9046-3

healthychildren. (2019). Sensory Integration Therapy. HealthyChildren.org. https:// www.healthychildren.org/English/health-issues/conditions/developmental-disabilities/ Pages/Sensory-Integration-Therapy.aspx

Justus, S. A., Powell, P. S., & Duarte, A. (2021). Intact context memory performance in adults with autism spectrum disorder. Scientific Reports, 11(1). https://doi.org/10.1038/ s41598-021-99898-2

Lau, B. K., Emmons, K. A., Adrian, Munson, J., Dager, S. R., & Estes, A. M. (2023). The prevalence and developmental course of auditory processing differences in autistic children. Autism Research, 16(7), 1413–1424. https://doi.org/10.1002/aur.2961

Stevenson, R. A., Ruppel, J., Sun, S. Z., Segers, M., Zapparoli, B. L., Bebko, J. M., Barense, M. D., & Ferber, S. (2021). Visual working memory and sensory processing in autistic children. Scientific Reports, 11(1), 3648. https://doi.org/10.1038/s41598-021-82777-1

Thye, M. D., Bednarz, H. M., Herringshaw, A. J., Sartin, E. B., & Kana, R. K. (2018). The impact of atypical sensory processing on social impairments in autism spectrum disorder. Developmental Cognitive Neuroscience, 29(29), 151–167. https://doi.org/ 10.1016/j.dcn.2017.04.010