For Williams syndrome patients, a larger fusiform face area (FFA) of the brain has been found to translate to increased face-to-face interaction tendencies, Stanford researchers said.

In a paper published in the Journal of Neuroscience last week, Stanford researchers found that behavioral tendencies in Williams syndrome patients correlated with FFA size, a finding that holds wider implications for other behavioral disorders like autism.

Those affected by Williams syndrome, a genetic disorder that includes both cognitive deficits and strengths, have a strong “social appetite,” said lead author and psychology department researcher Golijeh Golarai.

Golarai collaborated with Kalanit Grill-Spector, associate professor of psychology, and Allan Reiss, School of Medicine psychiatrist and neuroscientist.

Reiss had previously observed pronounced deficits in the temporal and occipital lobes of Williams syndrome patients. His knowledge combined with the known social nature of the disorder gave Golarai a “hunch” that Williams syndrome patients’ cortical regions would show a larger activation for faces.

“The logical question was, if the structure has an abnormality, then does the function?” Golarai said.

In conjunction with Harvard Medical School, the Salk Institute for Biological Studies and Bangor University, the Stanford research group began running functional magnetic resonance imaging (fMRI) on adults with and without Williams syndrome.

The FFA, which processes identity, usually activates when shown pictures of faces. The fMRIs allowed researchers to measure the size of each individual’s FFA. Those with Williams syndrome had a larger FFA consistent with their increased behavioral responsiveness to faces.

However, other parts of the brain associated with facial recognition showed no significant differences in this study, suggesting that Williams syndrome has a “specific effect in the fusiform gyrus for faces,” Golarai said.

The specificity of the FFA could suggest that it is uniquely plastic.

Conversely, the specificity could reflect the possibility that the experiment was not designed to process other parts of the brain involved in facial recognition.

“The kinds of faces we used weren’t designed to process the STS,” or superior temporal sulcus, a brain structure that reads expression, Golarai said. “We can’t say the STS is or isn’t normal.”

Next, the team hopes to conduct a similar study on children to determine whether or not Williams syndrome patients’ FFA size differs from the beginning of life or diverges with development from the normal size.

If FFA size diverges over time it “gives more weight to experience, but doesn’t eliminate genetics,” Golarai said.

Golarai is hopeful that understanding the interplay of genes and experience might provide hypotheses for possible genetic causes of autism.

“Autism is really an umbrella term for a whole collection of more specific diseases and disorders about which we know very little,” Reiss said. “We know what causes the behaviors that we call autism in less than ten percent of the people that receive that diagnosis.”

Autism and Williams syndrome represent “two sides of the same coin,” Reiss said. Social communication and behavior is overdeveloped in Williams syndrome and underdeveloped in autism.

Because Williams syndrome is a very specific disorder with known genetic factors, it can be used as an “experiment of nature” to better understand the subdivisions of autism, Reiss said.

Since Williams syndrome patients have larger than normal FFAs and autistic patients have “underactive” or smaller than normal FFAs, Reiss speculates that perhaps the same gene underlies both diseases, but different mutations account for the behavioral differences.

Hypothetically, the gene may affect how infants learn the context for facial interactions. One version could cause excessive social drive resulting in behavior characteristic to Williams syndrome, while a different version could cause an “abnormally decreased drive to interact with people which might serve as a basis for how some people come to develop autism,” Reiss said.

This speculation about gene-environment interactions could help explain a few more autism diagnoses in what Reiss believes will be a progressive discovery of the science behind autism.