Difficulties with language processing are common among people with autism spectrum disorder (ASD). While researchers are not certain what causes language delays, the problem may lie in the way autistic brains process sound. A new study from the Children’s Hospital of Philadelphia confirms previous research that the brain’s auditory processing abilities are abnormal in children with ASD. Specifically, the mechanism of auditory processing may mature slower in children with ASD. Although the results are not definitive, they do suggest that sound processing issues in autism play a role in other aspects of the disorder.
The researchers administered a battery of tests to 52 children with ASD and 63 typically developing children, all between the ages of 6 to 14 years. First, they used magnetoencephalography (MEG) to measure how quickly neurons on the right and left sides of the brain responded as the children listened to barely audible beeps. Next, they used structural magnetic resonance imaging (MRI) to locate the active neurons they identified in the MEG. Finally, they measured gamma rhythms, a type of high-frequency brain wave, which change in response to sound and are thought to be abnormal in autism.
Auditory processing in autistic brains lags compared to processing in typically developing children. The results confirm prior research that there is a delay of 11 milliseconds in auditory processing among older children with ASD. The auditory cortex typically becomes more efficient as people mature, responding in about 200 milliseconds after exposure to a stimulus in children under 10 years, in 130 milliseconds for older children, and in 100 milliseconds for adults. A slower response to auditory stimuli suggests that the auditory cortex develops slower in children with ASD, since auditory responses typically become more efficient with age.
The study also found that gamma rhythms were harder to detect in children with ASD than in typically developing children. This is consistent with previous research suggesting that gamma rhythms may be related to auditory processing issues in ASD.
“If it takes longer to process very basic auditory information like tones, this delay is going to become more prominent when you’re trying to encode more complex information like words and sentences. So this delay starts to build up, and everything starts to be delayed when you’re dealing with complicated linguistic information,” explained lead researcher J. Christopher Edgar, associate professor of radiology.
The researchers state that a longitudinal study is necessary to confirm whether the auditory cortex’s development is truly slower in children with ASD.
This research is published in the journal Molecular Autism.