Autism Linked to Excessive Early Brain Growth
Autism is devilishly difficult to diagnose at an early age. Ambiguous symptoms—delayed language, poor attention, emotional withdrawal—generally appear between the ages of 2 and 3. Parents may seek the wrong treatment, or worse, the condition may go unrecognized. A study published in the July 16 issue of The Journal of the American Medical Association suggests that doctors may be able to anticipate the onset of autism much earlier by using a simple tool: a tape measure.
Researchers from the School of Medicine at the University of California at San Diego analyzed medical records of 48 autistic children and found that small head circumference at birth, coupled with a sudden excessive increase in head size during a child’s first year, appears to be linked with autism. The most severely autistic children were those whose heads grew the fastest.
Eric Courchesne, the principal author of the study, says that the “burst of extreme growth” is primarily in the frontal cortex—the center of complex cognitive functions—and typically lasts only a few months, ending somewhere between the sixth and 14th month of life. At that critical stage, brain cells begin developing in response (and in proportion) to the baby’s first experience of the outside world. Too-rapid growth, outpacing what Courchesne calls “the guidance of experience,” may produce so much “neural noise [that] the infant would lose the ability to make sense of its world and withdraw.”
The fact that the accelerated rate of brain growth occurs in an infant’s first year suggests that autism springs from a genetic or prenatal biological cause, not from later environmental factors such as vaccinations, adverse allergic reactions, or exposure to toxins. Perhaps most important, it opens the way to earlier diagnosis and treatment. And as Courchesne observes, “the earlier the intervention, the better the outcomes of therapy.”
—Michael W. Robbins
Scientists See Yet Another Reason to Go to the Gym
Everyone knows that aerobic exercise is usually good for your heart. Now it turns out to be good for your brain as well. From about age 30 onward, everyone loses brain cells—both gray matter, or neurons, where conscious thinking takes place, and white matter, or axons, which serve as a connective network. This cellular loss is matched by an overall decline in cognitive performance. But researchers have found that cardiovascular fitness helps keep brain cells alive and well.
Cognitive neuroscientists at the Beckman Institute of the University of Illinois at Urbana-Champaign and at Wayne State University in Detroit analyzed functional magnetic resonance images of the brains of 55 volunteers ranging in age from 55 to 79. “Essentially, it was like an epidemiological study,” says Stanley J. Colcombe, a Beckman Fellow and the team leader. “We took a big sample, held for variables, and looked at what was left. It was known from prior animal studies that cardiovascular health had effects on brain health. So we went looking for the impact of fitness on cortical density.”
The volunteers ranged from couch tubers to marathon runners. The researchers first established fitness levels by means of a one-mile walk and a treadmill stress test. Then they examined the density—the concentration of functioning cells—in the gray matter and the white matter of each subject’s brain. After factors such as diet, education, tobacco use, alcohol consumption, and hypertension were statistically controlled to isolate the effect of exercise, the team found a clear correlation between greater fitness and greater brain-tissue density.
Unfortunately, taking up cardiovascular exercise upon, say, retirement, won’t restore those brain cells you’ve already lost. But, says Colcombe, it certainly will improve the cognitive performance of what you have left.
—Michael W. Robbins