What is it about the brains of people with autism that makes them so different from people with other types of mental retardation, such as Down Syndrome, or other types of mental illness, such as schizophrenia? We still don’t know what’s driving the autism epidemic that began in the 1980’s, but the study of autism has taught us a lot about the social brain. The new concept of autism spectrum disorders describes the many ways our social brains can fail.
Our social brain is built on at least five areas and capacities, according to neuroscientist Eric Kandel in Age of Insight (p 411 fig 25-2). Most infants demonstrate in the first days of life the capacity to recognize a face. This capacity is located in the inferotemporal cortex and the amygdala. Equally important is the capacity to recognize and attend to human bodies and to analyze their motions, located in the extrastriate body of the occipital lobe and the superior temporal sulcus. Most infants can distinguish a mother’s outreaching hand from a doll’s hand or Mr Rogers’ wave on TV.
The capacity to simulate the motions of others through mirror neurons gives the infant an internal representation of the gestures of others. Mirror neurons for movements, which fire during a gesture and during the observation of a similar gesture in another person (the outreaching hand, the smile), are concentrated in the inferior parietal cortex and inferior frontal cortex. Mirror neurons help babies (and big people) to learn by imitation. Overlying these capacities is the capacity to infer intentions, based on memories, and to imagine what another person is thinking (“Here comes the breast. Usually warm milk comes next. She wants to feed me.”)—the beginnings of empathy.
The social brain is a complex set of systems, with many opportunities for failure. Some autistic children seem unaware of the presence of another person in the room, suggesting an inability to attend to human bodies or analyze their motions. Others may notice another person but appear indifferent. Among those who glance at a face, many autistic children miss the important cues about the other person’s state of mind.
Why? Eye tracking studies of autistic infants looking at faces found that, unlike most infants who concentrate their attention on the eyes as well as the mouth, autistic infants focus on the mouth. At an early age they miss the eyes and all the information about the mind of the other person that comes through the eyes. They may miss that critical period when children learn that people can be understood in this way. The areas of the brain that respond to eye, hand, and arm movements are relatively quiet when the infant is tracking the motion of a truck or a rubber duck. It’s possible to be quite talented at observing things and quite impaired at observing and making sense of human behavior.
The payoff for all this new understanding of the social brain may come through intensive efforts to identify as early in life as possible those children who will later show forms of autism. Some promising early studies, such as the Early Start Denver Model suggest it may be possible with well-timed interventions to train autistic toddlers to improve their IQ’s as well as their adaptive behaviors, such as eye tracking, their reading of facial expressions, and their capacities to think about what others might be thinking. For most of us, the capacity for empathy is innate. For some it must be learned.