A human voice has no special ring to the
The findings, published Monday in the Proceedings of the National Academy of Sciences, lend support to the theory that social motivation lies at the heart of language and speech deficits that are endemic among children with autism spectrum disorder.
The social motivation theory of autism holds that deficits in communication and speech skills result from the brain's diminished ability to build a social context for human voices. Infants do not experience a mother's voice as soothing and cannot attach associations to its changes of tone, pitch and intonation.
"If the human voice, the mother's voice, is not sufficiently engaging to a child because it is not perceived as rewarding enough, then the attention to the human voice gets limited and there's no context for social communication and language-based communication," said Stanford neurobiologist Vinod Menon, lead author of the study.
The under-connectivity researchers found between the speech-sensitive area of the cortex and reward and emotion centers of the brain correlated strongly with tests that showed communication and speech deficits among the autistic children whose brains were scanned, according to the study, which found no evidence that more fundamental areas of sound processing were different in autistic brains.
"The deficits are not in basic auditory processing; the deficits are in the way that they might attend, or be motivated to attend the human voice," Menon said. "There's a strong link between how aberrant the circuit is and how much language communication deficits there are."
Studies comparing early learning that incorporates human voice and contact, versus solitary audio-visual methods without human contact, have suggested that cognitive skills likewise pass through a "social gateway" that is blocked in the autistic brain.
"Humans are a uniquely social species and children learn a huge proportion of their knowledge base through social interactions," said Coralie Chevallier, a scientist at the Center for Autism Research at Children's Hospital of Philadelphia, who has examined communication issues among autistics, but was not involved in the study.