Autistic Men Have Imbalance in Excitation in “Social Brain” Regions
Sat, April 10, 2021

Autistic Men Have Imbalance in Excitation in “Social Brain” Regions


Autism or autism spectrum disorder (ASD) is a developmental disability that can cause behavioral, communication, and social challenges. Many children and adults diagnosed with ASD take a great deal of time to develop social skills so they can interact successfully with others. There are a lot of mysteries about its causes and the theories of autism are diverse. One key theory of autism is rooted in the imbalance in levels of inhibition and excitation in their brain.

Inhibitory and excitatory signals in the brain

Inhibition and excitation work like the yin and yang of the brain. Inhibitory signaling makes the cell less likely to be active while excitatory signaling does the opposite. The inhibitory activity outweighs the excitatory activity in non-autistic individuals.

A new study published in Genetic Engineering and Biotechnology News (GEN) takes this leading theory of autism one step further. It found that autistic men, but not women, have an imbalance in their excitation in certain brain regions, which are important for self-reflection and social cognition. This is why it could differentially affect how they socialize and communicate.



Enhanced neural excitability in autistic men

Stavros Trakoshis from the Laboratory for Autism and Neurodevelopmental Disorder (LAND) at  Istituto Italiano di Tecnologia (IIT) and the team shared most of the evidence that supports the inhibition-excitation imbalance in people with autism come from studies of rare mutations that occur on the sex chromosomes or influenced by androgen hormone, which regulates the maintenance and development of male characteristics. Also, most people with autism do not posses such particular mutations.

Before their study, it remains unclear whether the theory can be applied to everyone with ASD or only to specific groups based on their gender and sex. They believe it is particularly important, considering that men and boys are about four times as likely to be diagnosed with autism than women and girls.

In Australia, for instance, the autism prevalence in males is 0.69% and 0.24% for females. Other countries highlighted by scientific online publication Our World in Data includes New Zealand (0.65% males, 0.23% females), Japan (0.61%, 0.22%), England (0.59%, 0.20%), Canada (0.57%, 0.19%), Singapore (0.57%, 0.20%), United States (0.55%, 0.17%), and Ireland (0.52%, 0.18%).

Trakoshis and colleagues have now found a way to determine whether an imbalance in inhibition or excitation in the brain happens differently in autistic men and women. Through computer modeling, the team recognized a signal in the brain scans of mice that corresponds to inhibitory and excitatory imbalance.

After knowing that the technique works to identify real increases in the excitation, they then looked for the biomarker in the brain scans of people with and without autism. All participants were identified with the gender that matches the sex they were assigned at birth. The result shows that autistic men do have an imbalance of excitation and inhibition in certain “social brain” regions, the authors explained. These brain regions include the medial prefrontal cortex. However, they did not observe the same imbalance among women with autism.

Based on previous studies, women with autism are better at camouflaging or hiding their differences when communicating or socializing than men with autism. Trakoshis and the team said that the better a woman at hiding her autism, the more her social brain activity resembled that of non-autistic women. Yet, studies have shown that friendships and romantic relationships pose unique challenges for both men and women with autism. This has led to a belief in others that they don’t want friends when, in reality, they long for connections just like other people. It’s only that they face unique challenges in forming and maintaining these relationships.



Why autistic people have trouble making and keeping friends

University College London's Director of Centre for Research in Autism and Education Liz Pellicano and graduate student Felicity Sedgewick, who were both not involved in the recent study, said that autistic women, in particular, may find it difficult to interpret the social subtleties that friendships entail. They have difficulty in responding to social conflict, dealing with social anxiety, and understanding the unspoken romantic signs.

The majority of what we know about friendships in autism are those studies in kids whose friendships are less complex than adults. There were also few studies on relationships in autistic adults but focus more on men.

Pellicano and Sedgewick interviewed 15 autistic women and 15 neurotypical women (not affected by a developmental disorder) aged 20 to 40. They asked them questions about friendships and other relationships. For instance, “How do you choose your friends?” and “What is it about friends that are important to you?”

They found that autistic women tend to view friendships as neurotypical women do. They also value the opportunity to share emotions and thoughts with friends. However, there were some important differences they identified. For example, neurotypical women tend to have large groups of friends while autistic women tend to have few intense and close friendships. Sometimes, intense friendships can become similar to “special interest,” one participant said.



Autistic women likewise respond differently to acts of social aggression, such as being suddenly cut off by a friend or hearing gossip. Many of the experience social anxiety, limiting them to socialize. It is also because of said anxiety that they approach social interactions differently. One woman said she needs to keep her interaction with others brief because of anxiety.

Whether girls and women or boys and men, discussing social rules and getting social experience are good ways to make socializing more rewarding and easier.

This year, Autism Speaks reported that approximately 1 in 54 children in the US are diagnosed with autism. The prevalence is 1 in 34 boys and 1 in 144 girls. An estimated one-third of people with autism are nonverbal and 31% of kids with ASD have an intellectual disability with significant challenges in their everyday function. Nearly 28% of 8-year-olds with ASD have self-injurious behaviors, such as skin scratching, arm biting, and headbanging.

The biomarker used by Trakoshis and the team can be helpful in future studies, like in monitoring responses to drug treatments. It could also be used to better understand other neurodevelopmental conditions that affect men more than women, including attention-deficit hyperactivity disorder.