LAWRENCE — A researcher from the University of Kansas Life Span Institute is part of an international group that recently published a comprehensive review of differences in sensory processing for people with autism during the prenatal (in utero) and neonatal (birth to a few months old) phases of life. The report appears in the peer-reviewed journal Psychological Review .
Sensory processing — or, how we experience sights, sounds and touch — can be "really different" in people experiencing autism, according to co-author Carissa Cascio, senior scientist with the KU's Life Span Institute and Kansas Center for Autism Research and Training .
"But sensory processing has been challenging to study for a number of reasons," Cascio said. "This paper tried to get at the very early developmental angle of how these systems for processing things like touch, vision and hearing first start to develop in the brain — and then to understand where that development may diverge in somebody who goes on to have autism versus somebody who doesn't."
Because autism spectrum disorder is tied to brain development that affects how people see others and socialize with them, studies tend to focus its social aspects. As for studying sensory experiences in autism, Cascio said most research tools are made for working with adults.
"They're designed for people who can sit and listen to sounds for 30 minutes while you run tests and experiments," the KU researcher said. "Therefore, we know a lot about where sensory processing ends up in adults or even in older children. But it's much harder to study — and much more theoretical at this point — when you're looking at the prenatal and early neonatal stages."
Still, Cascio said that focusing on earliest sensory processing can lead to breakthroughs in understanding and treating the disorder.
"We think that's really where we need to go as a field to try to understand what's happening across the lifespan in autism," she said.
The study reviewed and synthesized existing research on early sensory development instead of gathering new experimental data. The paper concluded by presenting several putative "cascades" or pathways by which very early sensory differences could impact the autism profile as it develops. One example of such a cascade is the prenatal brain map of the body, which is important for infants and toddlers learning to explore their environment and distinguish themselves from others, both foundations for building the social skills impacted by autism.
"We're hopeful that the ideas in this paper will help researchers formulate and test questions about early sensory development," Cascio said.
The model the KU researcher and her collaborators advocate is dubbed the "cascading effects model" — the idea that many symptoms of autism actually flow from differences in early sensory development.
"Our work is rooted in the idea that brain differences in autism are starting much earlier than the age at which we use complex social interactions to diagnose autism," Cascio said. "At the earliest stages, the brain is really geared toward just processing input and responding to it. If these very simple, early-developing pathways are being wired differently — and if we can understand the nature of those differences — that might give us an idea of how those differences cascade into the more complex behaviors that we use to diagnose autism."
Even as a researcher in the field of autism, Cascio said some of the paper's findings on sensory development in utero seemed extraordinary.
"I think some of what we found surprising were things that are happening even before birth," she said. "In the first seven to eight weeks of gestation the structures for our sense of touch are nearly fully developed — very early on, and a lot of that has to do with the prenatal environment."
She said the early development of humans' sense of touch probably boils down to the fact that it's almost the only sense to experience in the womb.
"Thinking about what it's like inside the amniotic sac, you're not getting much visual input, but you're getting some muffled auditory and a lot of tactile input from self-touch and from the ambient environment of fluid moving across the body," Cascio said. "That system is developing much earlier than a lot of the other sensory systems. That was something we kind of knew, but it was surprising to see just how early it was all in place."
Complicating the study of autism, which affects different people in different ways, are the varied cultures and backgrounds of people with autism, each of which places a different spin on personal touch or personal communication.
"That's something we think about a lot and is really under-researched at this point," Cascio said. "There are definitely cultural differences and family differences in terms of how much eye contact is expected, or how much touch is expected to be given and received. It might also be different for boys and girls."
Past that, the study of autism is made more complex by individual family dynamics: what might be sensory overload in one family might be perceived as too quiet or staid in another.
"Just the general ambient noise level in your home can come into play," Cascio said. "For instance, my family is big and loud and Italian. And my husband's family is Norwegian and very quiet. So, family dinners at the two places are very different in terms of how much input people have and expect. Those things all come into play as well."
The KU investigator said next steps in the line of research are experimental testing of the cascading effects developmental model; studies that combine sensory and social understanding of autism; further study of sensory system development at the earliest stages; and work that theoretically reframes autism as a disorder that first manifests in early sensory development.
