Riesenhuber adds that there is huge variation in the ability of individuals diagnosed with autism to discriminate faces, and that some autistic people have no problem with facial recognition.
"But for those that do have this challenge, it can have substantial ramifications some researchers believe deficits in face processing are at the root of social dysfunction in autism," he says.
The neural basis for face processing
Neuroscientists have used traditional fMRI studies in the past to probe the neural bases of behavioral differences in people with autism, but these studies have produced conflicting results, says Riesenhuber. "The fundamental problem with traditional fMRI techniques is that they can tell which parts of the brain become active during face processing, but they are poor at directly measuring neuronal selectivity," he says, "and it is this neuronal selectivity that predicts face processing performance, as shown in our previous studies."
To test their hypothesis that differences in neuronal selectivity in the FFA are foundational to differences in face processing abilities in autism, Riesenhuber and the study's lead author, neuroscientist Xiong Jiang, PhD, developed a novel brain imaging analysis technique, termed local regional heterogeneity, to estimate neuronal selectivity.
"Local regional heterogeneity, or Hcorr, as we called it, is based on the idea that neurons that have similar selectivities will on average show similar responses, whereas neurons that like different stimuli will respond differently," says Jiang. "This means that individuals with face processing deficits should show more homogeneous activity in their FFA than individuals with more typical face recognition abilities."
They tested the method in 15 adults with autism and 15 adults without the disorder. The autistic participants also underwent a standard assessment of social/behavioral functioning.
|Contact: Karen Mallet|
Georgetown University Medical Center