Functional MR scans have confirmed that levels of brain function are low or nonexistent in autistic patients viewing stimuli designed to provoke emotional activity, according to studies presented at the International Meeting for Autism Research held in early May in Seattle.
Research led by Dr. Susan Bookheimer, a professor of psychiatry and behavioral sciences at the University of California, Los Angeles's Semel Institute of Neuroscience and Human Behavior, and graduate psychology student Mari Davies gauged autistic children's reaction to direct-gaze and averted-gaze faces.
"Eye gaze is an important bonding and teaching tool for young children," Bookheimer said. "But autistic children tend to avoid the direct gaze. From a very early age, they do not orient toward the face. This led us to hypothesize that something unique must be taking place in the brain during direct versus averted gaze that might give clues as to the problems of autism."
Bookheimer and colleagues compared 16 typically developing children and 16 high-functioning children with autism, all between ages 8 and 14. While undergoing fMRI and wearing special magnet-compatible glasses, the children were shown a series of faces depicting angry, fearful, happy, and neutral expressions. Half the faces looked directly at the child, and half looked away. To assure that the children were looking into the eyes, researchers put crosshairs on the screen to focus the children's gaze and track eye movement.
The fMRIs exposed significant differences in activity of the ventrolateral prefrontal cortex, which has an intrinsic role in the experience of emotions. In the typically developing children, scans showed more blood flow to the ventrolateral prefrontal cortex when they were looking at direct-gaze faces and less activity when they were looking at the averted-gaze pictures. Brain scans of the autistic children, however, revealed no activity in this region, whether they were looking at the direct or the averted gaze.
"The results proved that the typically developing kids were engaging these brain regions, while the kids with autism were not," Bookheimer said. "The kids with autism were basically missing the significance of the emotional information conveyed."
In related research, UCLA scientists focused on the activity of the brain's mirror neuron system in autistic children. Led by Mirella Dapretto, Ph.D., an associate professor of psychiatry and biobehavioral sciences at the Semel Institute, this study confirmed that autistic children's inability to empathize and imitate was connected with dysfunction in the mirror neuron system.
Scientists used the same fMRI setup to measure brain activity, this time focusing on the mirror neuron system in the right inferior frontal gyrus. Twelve children with autism viewed and imitated faces depicting happiness, sadness, fear, and anger. FMRI revealed more brain activity in the children who tended to spontaneously imitate social behaviors or show empathy. The results confirmed previous research that impairment of the mirror neuron system correlates to the autistic child's ability to understand emotions, intentions, and actions.
Bookheimer and Dapretto are interested in seeing if they can manipulate the affected brain areas of children with autism by directing their attention more explicitly.
"We implicitly learn how to respond to emotions and how to empathize," Bookheimer said. "Nobody teaches us. The implicit learning system of autistic children seems to be impaired. We want see if explicit learning will help normalize their brain function. We will give them instructions on how to respond emotionally to what they see. The idea is to find an explicit learning system that will sharpen these areas of the brain."
The UCLA scientists also plan to examine the reward responses in the brain as they relate to autistic children.