Researchers have uncovered unique brain connectivity patterns in six-week-old infants at a higher risk for developing autism spectrum disorder (ASD). The study suggests that these early brain differences might contribute to the later emergence of ASD-related behaviors by affecting the typical development of social skills. These findings, published in Nature Communications Biology, suggest that the brain’s response to sensory and social stimuli begins to diverge much earlier than the symptoms of autism can be observed behaviorally.
Autism spectrum disorder is a developmental condition characterized by challenges with social interaction, communication, and repetitive behaviors. Early detection is crucial because it can lead to timely interventions that significantly improve outcomes for children with ASD. Previous research has shown that infants with an older sibling diagnosed with ASD are at a higher risk (approximately 20%) of developing the condition. However, identifying early biomarkers for ASD has been challenging due to the subtle and gradual emergence of symptoms.
The researchers aimed to investigate whether differences in brain connectivity could be detected in infants as young as six weeks old. They focused on the Salience Network, a group of brain regions responsible for detecting and filtering important stimuli and directing attention. Understanding how the Salience Network operates in infants at high risk for ASD could provide critical insights into the early neural mechanisms that contribute to the development of ASD-related behaviors.
The study involved 53 infants, divided into two groups: 24 infants with a higher likelihood of developing ASD due to having at least one older sibling with an ASD diagnosis, and 29 infants with no family history of ASD or other developmental disorders. All infants underwent resting-state functional magnetic resonance imaging (fMRI) at six weeks of age while they were naturally asleep. This technique allowed researchers to observe the brain’s activity and connectivity patterns without any external stimulation.
The focus was on the Salience Network, specifically its connections with sensorimotor regions (involved in processing sensory information and movement) and prefrontal regions (crucial for social attention and interactions). The researchers then tracked the infants’ behavior at age one, assessing sensory processing and social attention using standardized measures.
Infants at high risk for ASD showed stronger connections between the Salience Network and sensorimotor regions. This heightened connectivity might lead to an increased focus on basic sensory information, which could interfere with the development of social attention.
In contrast, infants at typical risk exhibited stronger connections between the Salience Network and prefrontal regions. These connections are important for directing attention to socially relevant stimuli, such as faces and voices.
There was an inverse relationship between connectivity to sensorimotor and prefrontal regions. Infants with stronger connections to sensory regions had weaker connections to prefrontal regions and vice versa. This suggests a trade-off in brain resource allocation between processing sensory inputs and attending to social cues.
These early brain patterns predicted behavior at one year of age. Infants with greater connectivity to sensory regions were more likely to show sensory over-responsivity, a condition common in ASD where individuals react excessively to environmental stimuli. On the other hand, those with stronger connectivity to social attention regions displayed better social attention skills, such as the ability to share attention with others, which is foundational for developing communication skills.
“An emerging theory in autism research is that differences in sensory processing may precede the more classic social and communication symptoms of autism, and this data supports that theory in showing that very early brain differences related to how attention is allocated may predict both sensory and social behaviors in toddlers,” said Shulamite Green, an assistant professor at the David Geffen School of Medicine at UCLA and corresponding author. “In other words, more attention to extraneous sensory stimuli in the environment could make it difficult to attend to social cues, and this difference in attention could really affect how the brain develops across the first year of life and beyond.”
“What I find compelling about these converging findings in such young babies is that they provide both a mechanistic and theoretical account for the lack of the typical attentional biases for social stimuli seen in older infants and toddlers who later receive an ASD diagnosis,” added co-author Mirella Dapretto, the associate director of the Semel Institute for Neuroscience and Human Behavior.
The findings from this study suggest that the neural foundations of ASD begin to take shape much earlier than previously thought. Detecting these early differences in brain connectivity could pave the way for interventions that address sensory processing issues and enhance social attention from infancy.
However, the study has some limitations. The sample size was modest, and brain connectivity was only evaluated at a single time point. The authors acknowledge that larger, longitudinal studies are needed to confirm these findings and to explore how these early brain patterns evolve over time.
Future research should also investigate the interplay between genetic and environmental factors in shaping brain connectivity and behavior. Understanding these dynamics could help identify specific interventions that could redirect attention to socially relevant stimuli and mitigate sensory processing challenges.
The study, “Salience network connectivity is altered in 6-week-old infants at heightened likelihood for developing autism,” was authored by Tawny Tsang, Shulamite A. Green, Janelle Liu, Katherine Lawrence, Shafali Jeste, Susan Y. Bookheimer, and Mirella Dapretto.