What images come to mind when you hear the phrase social brain? Do you think of children running around on a playground laughing together? Do you think of problem solving or imagine colorful brain scans? Do you think of autism? These are the questions that inspired a breadth of autism research that was recently evaluated by a team of Waisman scientists and compiled into a new literature review.
“The Development of the Social Brain in Baby Siblings of Children with Autism,” was published in March and explores the latest neuropsychiatric research on child and infant siblings with autism spectrum disorder (ASD). The article combines the many studies into a concise roadmap of the biological mechanisms behind social interactions in children with ASD. “There’s a lot of interest in understanding the developmental origins of autism, what happens in the brain, and what features in the brain early in life might be predictive or associated with the development of autism in general,” says Doug Dean III, PhD, assistant professor of pediatrics and medical physics and a Waisman Center investigator. Dean is first author on the paper. He co-wrote the review with fellow Waisman investigator Janet Lainhart, MD, a psychiatrist and professor in the School of Medicine and Public Health, along with Abigail Freeman, a UW genetic counseling intern. The three authors examine multiple studies published within the last 18 months to illuminate, in one paper, the earliest neural signs of ASD and their corresponding connections to cognition and behavior and what they cumulatively mean to the field of neuropsychiatry.
The social brain
“Because ASD is characterized by pervasive impairments in social interaction and social communication, understanding early development of the social brain is key to understanding ASD,” the authors say.
The three general categories of the social brain include: perception, or what social cues we intake from our senses; cognition, or processing non-verbal signs like body language, intentions, or situational context; and regulation, or the ability to control emotions or behaviors in social situations. “It is the different regions or mechanisms of the brain that are affiliated with social behavior,” Dean says of the many neural networks that process social information.
Impairments in social behavior become apparent at 12 months of age in many children who develop ASD, which is why it is important to study infants. “So you think of a baby being social, what areas of the brain is that baby using?” For example, when a baby begins to recognize its mother’s face and associate that face with positive feelings, specific areas of the brain are activated. But these activations in the brain do not always appear to occur in individuals with ASD, underscoring a need to look into the biological reasons behind behavior.
“We know that genetics play a significant role in the development of autism.” Freeman says. “We know that in some cases autism is associated with a single gene and in most cases, it develops because of the combined effects of many genes.”
All of the studies presented in this review include infant siblings of children with autism. “Infant sibling studies are trying to determine what areas of the brain are involved in the earliest abnormalities that can be detected in children who develop autism,” Lainhart says.
Through the neuroimaging studies referenced, this review makes clear that some infant siblings that go on to develop ASD have structural brain differences that are apparent at as early as 2 months of age.
“The baby sibling design is powerful for ASD research because genetic effects explain most of the risk for ASD,” the paper says. ASD has a heritability of 64 to 90 percent, meaning genetic factors account for a great deal of the development of ASD. Furthermore, Freeman says, “there is about a 20 percent chance that someone who has one child with ASD may have a second child with ASD.
Therefore, the benefits of studying infant siblings are that researchers can compare and contrast both behavioral and brain developmental differences in infant siblings who develop versus do not develop ASD and gain important insights into the early neural signs of ASD.
The literature review is a welcome addition to a growing body of neuropsychiatric research on ASD, and adds to the importance of understanding individuals who have it. Lainhart says “Autism in many cases comes with gifted abilities and unique characteristics that really add to our society and to our world,” she says. “The goal therefore is to identify as early as possible the brain mechanisms that underlie the impairing aspects of autism as well as the mechanisms underlying special abilities.”
This review also allowed the authors to incorporate their professional opinions into the text, “So we were not just reporting that ‘this project found this and this project found that.’ Instead, we could say, ‘This project found this and, in our opinion, it was an exceptional study,’” Lainhart says. Lainhart has dedicated her career to autism research and clinical services. Her findings have made highly impactful contributions to the field particularly in the area of brain development in individuals with ASD. Dean is a new investigator at the Waisman Center with extensive experience in early neurodevelopment and brain imaging.
The authors stress a difference between preliminary studies and studies that are replicated. “There are some interesting findings in the literature that have been replicated across different studies by different research groups or within their own research group as well,” Dean says. “And we feel that these kinds of findings are going to be some of the more important ones to focus on in thinking about early brain changes.”
He adds that the preliminary work that has not been replicated could provide opportunities for future research to discover whether the observations in those studies really are a phenomenon in individuals with autism. Further research in these areas, Lainhart says, could “lead to new interventions that decrease impairment related to ASD and help individuals with ASD do what they can do, improve their quality of life, and contribute to their fullest potential.”