For years experts have been keenly aware that many children and young adults with autism respond differently to facial expressions and other social cues. Some simply "don't get it" when confronted with a smile, shrug or other forms of nonverbal communication.
Now, a Hofstra University researcher and his team of fellow brain mappers have uncovered tantalizing evidence that helps explain why: There is a marked difference in the way blood flows to specific brain regions when people with and without autism observe "a happy face."
"This is a big piece of the puzzle," said lead scientist Keith Shafritz, an associate professor and chairman of psychology at Hofstra and an investigator at the Feinstein Institute for Medical Research in Manhasset. "We think we now know what's going on with emotional face recognition."see alsoFind top docs
He explored the brain to identify regions involved with recognizing nonverbal cues. And as much as his new analysis is about fostering a better understanding of autism, it's also about understanding the complex geography of the brain itself. The team found regions involved with recognizing "a happy face."
Their discovery arrives in the midst of several new analyses involving autism. One suggests the hormone oxytocin -- the so-called love hormone -- may play a role in improving social interaction skills. Another posits a "gut-brain" theory that bacteria leaking from the intestines affects the brain, and controversially proposes antibiotic therapy as a way to improve autism's symptoms.
Shafritz said social interaction problems pose one of the biggest obstacles for people with autism. "We wanted to explore the brain mechanisms that might cause problems for kids with autism when they are in social situations," he said.
It's relatively common for some with autism to become engaged in a monologue on an arcane topic and remain oblivious to others' facial expressions of disinterest.
Using MRI, scientists viewed brain activity in real time. The 38 participants ranged in age from 13 to 23 and included a group without autism and one diagnosed with so-called high-functioning autism.
While in the MRI tube, participants viewed photos of people smiling or expressing fear. During the "happy face" aspect of the task, Shafritz said scientists could see a copious flow of blood into the brain's ventral striatum, nucleus accumbens and anterior amygdala in participants without autism.
Among those with autism, there was no increased blood flow into any regions. Test subjects were essentially nonplussed by the smiles.
There was no substantial surge in blood flow to any brain region for either group when participants viewed pictures of faces expressing fearfulness. Shafritz said there are likely different reasons for the absence of brain activity in the two groups.
Scientists, he said, have long known the brain's amygdala has been associated with the perception of fear and may well be the seat of the "fight or flight" response. To people without autism, the faces may not have exhibited enough fearfulness to activate a response, he said.
For those with autism, Shafritz added, neuroscientists have been aware for years of an inability to recognize fearfulness. "Fear in others may be difficult for some people with autism to identify," Shafritz said.
His basic brain research arrives as scientists elsewhere explore disparate paths. Last month, British scientists reported that men with autism treated with a nasal spray of oxytocin were able to make better eye contact after treatment. People with autism often have difficulty making eye contact. The British study, however, has received mixed reviews.
Oxytocin is a natural hormone released during breast-feeding as well as sex, but a similar study last year involving autistic children found the oxytocin spray failed to improve social skills.
Last week, a study in the journal Microbial Ecology in Health and Disease suggested an antibiotic regimen aimed at destroying certain intestinal bacteria may lead to overall symptom improvement for children with autism. The report is based on one child.
Dr. Andrew Adesman, of Cohen Children's Medical Center in New Hyde Park, said the research is based on the discredited "leaky gut" theory of autism.
"Although autism researchers and supporters don't want to dismiss any credible clues, they also have to be judicious in their approach to setting funding priorities," he said.
Happy and Fearful
Keith Shafritz and colleagues have investigated why some people with autism do not understand nonverbal communication, such as the expressions on the faces of others.
-In people without autism, blood flow increases substantially in three regions of the brain when observing a smiling face.
-For people with autism there is no increased blood flow into the three regions -- ventral striatum, nucleus accumbens and anterior amygdala -- which Shafritz concluded are associated with recognizing the meaning of a smiling face.
-Neither group -- people with or without autism -- showed any blood flow changes in the brain when they observed a face expressing "fear." For those without autism, the face probably didn't appear especially fearful. For those with autism, fearfulness on the faces of others is rarely, if ever, understood, Shafritz said.