Early Childhood Development of Autism: The Brain, connections to Anxiety and Gender Differences, and the Application to Learning from Experience

Early Childhood Development of Autism: The Brain, connections to Anxiety and Gender Differences, and the Application to Learning from Experience

Natalia Baron UA’26 and Jim Stellar

Early childhood is a vital time for psychological development. From the time of birth a child’s brains grow at a rapid pace as they begin to learn basic cognitive abilities such as pre-reading, language, memory, and vocabulary. However, during this time, it has been argued that there are gender differences in the brain that are reflected in different developmental times for boys and girls. For those who have Autism Spectrum Disorder, they develop psychologically, physically, and socially significantly differently compared to other children especially during the ages of 2-5. In that manner, girls tend to be more advanced in certain cognitive abilities compared to boys, who tend to surpass girls in aspects such as visual-spatial integration and more. Although both genders catch up with one another through later development, the question here is why do these early differences appear? And what can this inquiry teach us about brain circuits that underlie experiential education? We will come back to that.

To start with basic brain anatomy (see figure below), within 2-3 weeks after birth, the brain volume is around 35%, then it doubles in the first year after birth and continues to increase about 15% to reach around 80% of adult size in the second year. After age 2, the brain volume increases more gradually, but white matter (orange line) volume also expands throughout adolescence and a bit beyond. However, notice that within the first year after birth, white matter only increases by roughly 11% while the volume of the cerebral gray matter increases by 108-149% from age 1 to 2. As an aside, after childhood it has been shown that white matter development continues slightly even into the college years, as is indicated by the right side of the graph below in the orange line.

Now turning specifically to the autistic brain compared to the brain of those without ASD, there are a few differences that stand out. To start, studies indicate differences in the amygdala, the area of the brain that seems to be responsible for producing emotions, especially fear and anxiety. Studies also suggest that the amygdala size varies in those with ASD, being initially larger in early development, but then also smaller later on in development. These differences also vary with gender.  Let’s unpack this finding a bit.

Anxiety in autism

Anxiety is a common condition in many children, however it is more common in those who have autism. According to a study, “Data on the prevalence of anxiety in individuals with autism have varied widely, ranging from 22 to 84%.” They go on to say, “A recent meta-analysis found that the prevalence of at least one anxiety disorder among children with autism was 39.6%. Out of 108 high-functioning children with autism, 91.6% met criteria for two anxiety disorders being social phobia (41.7%) and generalized anxiety disorder (25.9%).”

As a result, their lack of social skills and difficulty navigating sensory environments. Other research has shown that the most common form of anxiety in autism is specific phobias. Any person with a phobia experiences extreme distress whenever they may be exposed to a triggering situation. There are four ways that explain the anxiety-autism interaction. First, attention to detail – children with autism tend to be more detail focused. Due to their intense focus, it makes it more difficult for children to change their routine. If the shift in routine happens before they are ready or too quickly, anxiety is the result. Second, sensory sensitivities – those who have autism experience their sensations more intensely compared to those without autism. With overwhelming sensory experiences, it too may trigger anxiety. Third, social situations and language – in those with autism there is an immense pressure to follow social rules, which can increase anxiety. Fourth, because those with autism process language differently, they tend to experience anxiety when trying to express their needs and wants verbally.

Role of the amygdala in autism anxiety – two types

Studies have shown that the amygdala is one of the main areas of the brain that is activated in those with anxiety, and this also true for autism. While the connection between anxiety and autism is still being researched, researchers have discovered similarities and differences between autism and normals. In an article published by the MIND institute at the University of California, psychologists who conducted a study on types of anxiety in children with autism, compared to non-autistic children, showed that half of the children with autism had Diagnostic and Statistical Manual (DSM) anxiety, diagnostic and statistical manual of mental disorders, while the others had what is called autism-specific anxiety.

Autism-distinct anxiety is a form of anxiety that includes fears that are related to social confusion, e.g. facial expressions or specific sounds. Autism distinct anxiety involves the fear of losing access to a special interest. For example, if a child with autism spectrum disorder has a disruption in their routine, such as not being able to do puzzle time, they may worry more than usual. According to a recent study, this specific type of anxiety that is more common in those who have autism spectrum disorder, “tend to have unusually small amygdalae, specifically on the right side. As mentioned in the study above, an applied psychologist states that autism-distinct anxiety may be associated with social stress, an over-activated stress system in the brain could have downstream effects towards the amygdala and other brain regions that are responsible for emotion, learning, and memory.

Traditional anxiety, or otherwise other anxiety disorders that are classified by DSM, for example social anxiety or specific phobias also affects those with autism spectrum disorder. In the same study, research shows that those who have traditional anxiety and autism spectrum disorder have significantly larger amygdala volumes compared to those with autism specific anxiety disorder. In a 2022 study, researchers found that “autistic children with DSM anxiety had the largest amygdala volumes compared to other groups, with significantly larger right amygdala volumes compared to traditional DSM at both ~3 and ~11 years of age. It is important to emphasize that amygdala enlargement in autistic children with DSM anxiety was already present at 3 years-of-age, before clinical anxiety is typically diagnosed.” Therefore, researchers believe that the reason for an enlarged amygdala related to DSM anxiety occurred during early postnatal period, allowing psychologists to believe that an enlarged amygdala may be a sign or marker of traditional anxiety in those with autism spectrum disorder instead of autism distinct anxiety.

Back to gender differences in autism

Autism is more common in boys than in girls, as a matter of fact, in a recent study, boys are four times more likely than girls to receive an autism diagnosis. Researchers believe that autism is more frequent in boys because most studies were male predominant samples. In the same study, looking at brain differences between girls and boys with autism, a Yale study that included 45 girls and 47 boys with autism alongside with 45 girls and 47 boys without autism, researchers focused on how the brains of young people with and without autism process human motion. Yale researchers found that while, “Using brain imaging technology called functional magnetic resonance imaging, researchers found that the accepted wisdom that the posterior superior temporal sulcus region, an area associated with the crossmodal binding of both auditory and visual senses, constitutes a ‘neural signature’ for autism was primarily true for boys.

In neuroimaging done on girls, however, they found that a different region of the brain called the striatum, which controls cognition, reward, and coordinated movements, is involved”. Therefore, while doctors are diagnosing children with autism, due to past procedures and evidence that was done on male subjects primarily in the past, medical professionals are searching for the “neural signature” for autism is in the posterior superior temporal sulcus region, it may have more difficult to identify autism in girls because the “neural signature” is found mostly in the striatum, causing autism in girls to be overlooked and misdiagnosed.

Combining gender and the amygdala/anxiety in autism

On the other hand, in a different study, there is a difference between girls and boys with autism is the size of the amygdala in girls. “A 2020 study showed that the amygdala is more affected in autistic girls than in autistic boys. An enlarged amygdala is associated with more severe emotional problems specifically in autistic girls, according to other work”. Due to girls being more affected by the amygdala, it can explain why girls with autism have trouble identifying others’ facial expressions or how to identify what another person is feeling by looking at their face.  Although the role of the amygdala in those with autism is still being looked into, the amygdala still plays a vital role in those with autism. Other than the differences between boys’ and girls’ emotional processing in autistics, there are differences in white matter. Autistic girls tend to have an increased measure of structural integrity specifically in the corpus callosum compared to girls without autism, while in boys, the measurement is lower in autistic boys compared to non-autistic boys.

Relation between autism, anxiety and experiential education

Now how does learning from experience as a strategy interact with this blog on autism and gender? The answer is that both show the operation of two levels of processing in the brain that our lab website refers to as “Heart” and “Head” reasons. The latter is the conscious planning, thinking, talking, the operation that we do all the time and tend to think that this is all there is. The second is the emotional, evaluative, value-generating aspect of our thinking of which we can be unaware. Hence the quote we use all the time from the 1600s philosopher and mathematician, Blaze Pascal, “The heart has reasons of which reason does not know.”  It applies to both, and each area of inquiry can learn from the other, we believe.