Autistic teens less responsive to unfamiliar voices, Stanford study finds

Autistic teens less responsive to unfamiliar voices, Stanford study finds

Teenagers on the autism spectrum often share a common desire with their neurotypical peers: the urge to build new friendships, find people with shared interests, and pursue romantic relationships. But new research from Stanford Medicine suggests a neurological hurdle may be hindering these social ambitions.

A study led by Stanford Medicine and published July 13 in Proceedings of the National Academy of Sciences reveals that the brains of autistic teenagers do not become increasingly responsive to the voices of strangers as they mature. This stands in direct contrast to neurotypical adolescents, whose brains show an uptick in responsiveness to unfamiliar vocal stimuli during this life stage.

According to Daniel Abrams, PhD, clinical associate professor of psychiatry and behavioral sciences at Stanford Medicine, tuning into new voices is essential for making new social connections. Our results point to adolescence as a period when, for some kids with autism, their brains are not becoming increasingly responsive to unfamiliar vocal stimuli, Abrams said. Their brains did not show an uptick in responding to new voices like the neurotypical kids did.

The Neural Divergence of Adolescence

The research team studied 79 participants between 7 and 17 years old, including 39 with autism spectrum disorder and 40 typically developing participants matched for sex, IQ, and age. Using functional magnetic resonance imaging (fMRI) scanners, researchers tracked brain activity while participants listened to three types of audio: nonsense words spoken by their mother, the same nonsense words spoken by two unfamiliar women, and environmental sounds, such as a running dishwasher. The use of nonsense words, such as keebudishawlt, was designed to prevent the brain from engaging regions that process the meaning of words.

The findings highlight a distinct difference in how "social" brain centers operate. In typically developing teens, brain regions focused on salience—which directs attention—and reward centers responded more strongly to voices as the teens grew older. In autistic teens, these centers did not show increased responsiveness. In some older individuals with autism, these brain regions were actually less responsive to voices than they had been in younger children with autism.

Furthermore, the study found a reversal in how teens prioritize familiar versus unfamiliar voices:

• Neurotypical teens: Showed a strong pattern of tuning in more to unfamiliar voices than to their mother's voice as they matured.
• Autistic teens: Became increasingly attuned to their mother's voice compared to unfamiliar voices.

Abrams noted that this preference for the mother's voice was most pronounced in teens with the most severe autism symptoms. Instead of tuning into unfamiliar voices during adolescence, they were tuning in more to the sound of their mom than at younger ages, Abrams said, adding that this likely reflects the social communication challenges these adolescents face.

A Lifetime of Voice Processing

Autism is a developmental disorder affecting 1 in 31 children. It is characterized by repetitive behaviors, restricted interests, sensory aberrations, and social difficulties, including struggles with eye contact and interpreting facial expressions. Voice processing is often one of the first indicators of the condition; for example, a young child may not respond to the sound of their own name.

Prior research by Abrams’ team indicated that children with autism aged 7 to 12 struggle to pick up emotional cues in voices.

Vinod Menon, PhD, the study's senior author and professor of psychiatry and behavioral sciences, emphasized that autism is not static. We tend to think of autism in terms of what the brain does differently, but not enough about how those differences unfold with age, Menon said. The way the brain attends to socially relevant information is reshaped throughout adolescence, and in autism that developmental process appears to follow a different course.

Implications for Therapy

Because the brain remains plastic throughout adolescence, researchers believe this period represents a golden opportunity for intervention. Abrams pointed out that most autism treatments focus on preschoolers, leaving far fewer options for teenagers who are often enthusiastic about building social bonds.

Understanding these specific neurological patterns may allow the medical field to develop therapies tailored to the adolescent brain. The study was supported by an anonymous philanthropic donation, the Swiss National Science Foundation, the Brain and Behavior Research Foundation, and the National Institutes of Health (grant K01MH102428), with contributions from researchers at ETH Zurich and the University of Zurich.