Paintings of trees with spindly brown branches and plump green leaves cover the walls. Books, plastic cars and coloring books spill out across the carpeted floor and fill several plastic bins.
The children who come here are as young as 3 months on their first visit, and return every few months to participate in a battery of tests of their social behavior and perceptual processing — the brain’s response to non-social stimuli, such as looking at an ordinary object.
About one in four of these children is particularly interesting to the researchers: They are the younger siblings of children with autism, and are much more likely to develop the disorder than are those without a family history of it. Over the past few years, scientists have gathered heaps of behavioral data from these so-called ‘baby sibs’, but the Baby Lab is among the first to look for distinct signatures of brain activity.
The lab’s studies are ongoing, but two published reports have uncovered surprising differences between baby sibs and age-matched controls. Previous imaging work on face processing in people with autism had found abnormalities, suggesting to many researchers that their brains are slow to process social information. But the Baby Lab team is finding that during tests of sensory or perceptual processing, baby sibs show abnormally fast brain responses, rather than a delay.
Lead investigator Karen Dobkins says these data suggest an alternate interpretation of autism’s origins. Instead of resulting from a disruption of the brain’s social behavior circuits, she says, the disorder could arise from early upsets in perceptual processing, which eventually cause more noticeable social problems.
“We know that the hallmarks of autism are social in nature, but social systems develop later than sensory systems,” says Dobkins, professor of psychology at UCSD. “How on earth are you supposed to respond appropriately, behave appropriately, if you don’t perceive your world properly?”
This hypothesis agrees with previous reports from other labs conducting baby sib research, which converge on the idea that there is no fundamental social problem in autism, but rather gradual deficits in several different perceptual and sensory systems, according to a review of these studies published in June.
Chicken or egg?
The Baby Lab tests children for different abilities as they grow up. At 3 and 6 months of age, for instance, the infants sit on their mothers’ laps and watch gray lines flash on a computer screen — allowing researchers to assess how well they detect visual contrast. At 10 and 18 months, the toddlers wear electrodes on their scalp, allowing researchers to record brain activity during perceptual tasks, such as looking at pictures of faces or objects, and social ones, such as playing with a new toy along with their mothers.
The lab’s newest study, to be published in the 15 November issue of Biological Psychiatry, found that 10-month-old baby sibs produce brain-wave responses to pictures of toys significantly faster than do controls.
The findings support a 2007 report from the researchers in which they found that, compared with healthy controls, 6-month-old baby sibs show twice as much sensitivity to black-and-white visual contrast. The researchers say this heightened ability stems from unusual robustness in an early visual brain pathway — one that feeds into brain areas responsible for processing emotions and facial expressions.
But others are skeptical, saying the heightened processing does not necessarily indicate that perceptual glitches are the root cause of the disorder.
“If that were true, then you wouldn’t have something so specific happening in the social domain. They would have visual problems, and more global forms of intellectual disability,” notes Ami Klin, director of the Autism Program at the Yale Child Study Center.
A fundamental social deficit also makes more sense from an evolutionary perspective, Klin adds. “The things in the world that are important to an infant’s survival are people, not objects. Why should they pay more attention to objects?”
In his own studies, Klin has found that, unlike healthy controls, toddlers with autism show no preference for human motion, and tend to look at other people’s mouths instead of their eyes.
The question of which deficits come first “is very much a ‘chicken or egg’ problem,” says Mayada Elsabbagh, scientific coordinator of the British Autism Study of Infant Siblings. “What’s going on is actually affecting multiple systems at the same time, in a way that we don’t see very clearly within the first year.”
…read the rest of my latest feature at SFARI
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