Striking Differences in the Social Brain Found in Children with ASD, "Unaffected" Siblings, and Typical Children
Connie Anderson, Ph.D.
IAN Community Scientific Liaison
Date First Published: May 27, 2011
Solving the interconnected mysteries of the autism spectrum has been incredibly challenging. For one thing, although they are alike in some ways, people with autism spectrum disorders (ASDs) have all kinds of differences. A nonverbal child with food allergies and gastrointestinal issues may have an ASD, but so may a talkative child with frequent meltdowns and anxiety. So far, the genetic picture has been just as varied, with countless tiny and different genetic changes associated with ASD.
Brain structure may be the common element. If varied genetic changes lead to the same kind of changes in the brain, we may be able to explain core similarities shared by people across the autism spectrum. In fact, autism researchers have recently discovered that regions of the brain associated with social awareness do not "activate" properly in individuals with ASD. Furthermore, some of these same differences in the brain are shared by seemingly unaffected siblings of children with ASD. "It is possible," wrote the researchers, "that the simplest and potentially most powerful signature of ASD will be found at the level of brain systems." 1
Before learning about these important findings, it is helpful to understand recent discoveries about biological motion, social awareness, and the social brain that paved the way for this research.
Biological Motion and Social Awareness
It has long been believed that humans, as social creatures, are wired to detect "biological motion." Biological motion is the movement of a human or animal, as opposed to tree limbs rocking in the breeze or waves surging on a beach. Only recently have researchers provided hard evidence of this.
One way that researchers have studied this is by using point-light displays. These are animated dots of light shown on a black background that hint at a person's outline and motion. Think how modern moviemakers create digital characters, such as Gollum in The Lord of the Rings or the aliens in Avatar. They place special markers all over an actor's body, record his motion as displayed by the markers, and then build upon this to digitally create a robot or other creature. Just a number of points need to be "captured" in order to define a character's motion precisely because we are able to perceive a creature moving based on very little (see Figure 1).
Researchers in Italy used point-light displays to study whether infants focus on biological motion more than other types of motion. They found that two-day-old babies pay more attention to a point-light display which mimics a walking hen than to a random pattern of lights. "The present data," they wrote, "are consistent with the existence in humans, at birth, of a predisposed and experience-independent perceptual mechanism for the detection and analysis of biological motion." 2 The idea is that we are wired to notice and focus on other living things over anything else from birth -- no learning is required.
Soon after the Italian study, other researchers showed that people pay greater attention to human biological motion than to animal biological motion. 3 Next, researchers at Stanford University reported that one-year-old children will actually follow the "gaze" of a human point-light figure, looking where it seems to be looking. This, they said, is the first evidence that our ability to pick out biological motion and our ability to read and respond to social cues work together. 4
ASD: Impaired Ability to Detect Biological Motion
Researchers at Yale University wondered if very young children with ASDs would be less drawn to focus on biological motion than other children. If awareness of biological motion and our social abilities are linked, would children with ASD, who have many social deficits, be less likely to notice and prefer biological motion over other kinds of motion? To find out, the research team showed point-light displays of a person-like figure to three groups of two-year-old children: children with ASD, typically developing children, and children with non-ASD developmental delays. 5
Some of the point-light figures were right-side up and some were upside down. It was already known that people tend to perceive the right-side up point-light figures as human, but not the upside down ones.
The results were intriguing. Both the typically developing children and the developmentally delayed (but not autistic) children paid much more attention to the biological motion of the upright, human-like animations. Only the children with ASD were random in their attention. They were just as likely to look at the upside down, less human-like figures as the upright, more human-like ones.
Watch the point-light displays the children saw, and observe where their attention was focused.
The researchers also noticed that if a sound accompanied a motion, so that the motion seemed to cause the sound, children with ASD paid very close attention to that. The children in the other groups completely ignored the motion and sound occurring together, maintaining their focus on biological motion and what the researchers called "socially relevant signals." The researchers thought that this attraction to co-occurring motion and sound might be the reason people with ASD often look at mouths when people are talking instead of at their eyes. 6 7 A mouth that is moving in sync with someone's speech may naturally draw their attention. Unfortunately, while looking at the mouth, they are missing all the social and emotional meaning conveyed by the eyes.
In sum, typical two-year-old children, and typical two-day-old children (as shown in the Italian study), prefer biological, social motion over random motion, but two-year-old children with ASD do not.
Neural Signatures: Bringing the Brain into It
Dr. Kevin Pelphrey and his team at Yale University wondered if these different responses to biological motion would be reflected in children's brain scans. If you took a functional magnetic resonance imaging (fMRI) scan while children were observing point-light displays of biological motion, would you be able to tell which children had ASD simply by looking at brain activity?
To find out, the team studied three groups of children: those with ASD, unaffected siblings, and typically developing children with no family history of ASD at all. The children, who ranged in age from 4 to 17, underwent a five and a half minute fMRI while viewing point-light displays. Some of the displays featured biological motion -- a human-like figure walking or playing patty-cake -- while others featured random motion. 1
The results were fascinating. The brains of children with ASD showed clear dysfunction in a number of regions that should "light up" when a person perceives biological motion. What's more, lack of activity in one of these, the posterior superior temporal sulcus (pSTS), was associated with a child's level of autistic social impairment: the less activity in this region of the brain, the more severe the child's autistic social deficits.
Most surprising of all was that the "unaffected" siblings had a much different response to biological motion than typically developing children. Even though the siblings had been screened to make sure they had no ASD traits and had similar behavior to the completely typical children, their brain activity was like that of their brothers and sisters with ASD. In addition, when they were viewing biological motion their brains also "lit up" in completely unique areas that were not active in the children with ASD or the typical children. The researchers proposed that the siblings might somehow be compensating for abnormal brain circuitry that was similar to that of their affected brothers and sisters. "It's possible that the development of these regions was one of the things that helped them to avoid having autism, despite having the genetic risk," Dr. Pelphrey said. 8
The three brain activity patterns were so distinct that a computer program alone, if fed a random brain scan, could predict which category a child belonged to by the pattern. 9 Of course, as with any important study, other researchers will now attempt to confirm or disprove these findings, and build upon them. Dr. Pelphrey himself is conducting additional fMRI scans of children participating in the Simons Simplex Collection, an innovative project collecting DNA, behavioral profiles, and developmental histories from families with just one child on the autism spectrum.
Children with ASD, who can be very sensitive to sound and lights, often have a hard time coping with the booming noise and bright glow of an MRI machine. See how Dr. Pelphrey's empathetic team uses the "Statue Game" to make having an MRI a fun experience for children participating in fMRI studies.
The discovery of distinctive brain activity patterns for individuals with ASDs and their siblings has great potential to advance autism research and clinical practice. By looking at the functioning of socially- activated regions of the brain, we may be able to tell who does and does not have ASD. We may also be able to tell who seems fine but carries (and perhaps overcame) genetic risk for ASD. There may come a time when a diagnosis of ASD -- and even a measure of its severity -- is based not just on observation of external behavior but on this "neural signature." In addition, new treatments focused on social deficits may intentionally target activation of crucial brain regions, while the effectiveness of older treatments might be measured by how activation of the social brain changes over time.
- Children with Autism and Siblings Share Brain 'Signature' -- an article on the Simons Foundation Autism Research Initiative (SFARI) website.
- Kevin Pelphrey: Charting the Course of the Social Brain -- a profile of the researcher on the Simons Foundation Autism Research Initiative (SFARI) website.
- Kaiser, M. D., Hudac, C. M., Shultz, S., Lee, S. M., Cheung, C., Berken, A. M., et al. (2010). Neural signatures of autism. Proceedings of the National Academy of Sciences of the United States of America, 107(49), 21223-21228. View Abstract
- Simion, F., Regolin, L., & Bulf, H. (2008). A predisposition for biological motion in the newborn baby. Proceedings of the National Academy of Sciences of the United States of America, 105(2), 809-813. View Abstract
- Pinto, J., & Shiffrar, M. (2009). The visual perception of human and animal motion in point-light displays. Social Neuroscience, 4(4), 332-346. View Abstract
- Yoon, J. M., & Johnson, S. C. (2009). Biological motion displays elicit social behavior in 12-month-olds. Child Development, 80(4), 1069-1075. View Abstract
- Klin, A., Lin, D. J., Gorrindo, P., Ramsay, G., & Jones, W. (2009). Two-year-olds with autism orient to non-social contingencies rather than biological motion. Nature, 459(7244), 257-261. View Abstract
- Klin, A., Jones, W., Schultz, R., Volkmar, F., & Cohen, D. (2002). Visual fixation patterns during viewing of naturalistic social situations as predictors of social competence in individuals with autism. Archives of General Psychiatry, 59(9), 809-816. View Abstract
- Jones, W., Carr, K., & Klin, A. (2008). Absence of preferential looking to the eyes of approaching adults predicts level of social disability in 2-year-old toddlers with autism spectrum disorder. Archives of General Psychiatry, 65(8), 946-954. View Abstract
- Hughes, V. (2010a). Children with autism and siblings share brain 'signature'. Retrieved May 24, 2011.
- Hughes, V. (2010b). Kevin Pelphrey: Charting the course of the social brain. Retrieved May 24, 2011.