单选题 Whether the cause is maternal anti-bodies, heavy metals or something else, there is no question that the brains of young children with autism have unusual features. To begin with, they tend to be too big. In studies based on magnetic resonance imaging (MRI) and basic tape-measure readings, neuroscientist Eric Courchesne at Children"s Hospital of San Diego showed that while children with autism are born with ordinary-size brains, they experience a rapid expansion by age 2—particularly in the frontal lobes. By age 4, says Courchesne, autistic children tend to have brains the size of a normal 13-year-old. More recent studies by Admiral and others have found that the amygdale, an area associated with social behavior, is also oversize, a finding Admiral believes is related to the high levels of anxiety seen in as many as 80% of people with autism.
Harvard pediatric neurologist Dr. Martha Herbert reported last year that the excess white matter in autistic brains has a specific distribution: local areas tend to be overconnected, while links between more distant regions of the brain are weak. The brain"s right and left hemispheres are also poorly connected. It"s as if there are too many competing local services but no long distance.
This observation jibes neatly with imagining studies that look at live brain activity in autistic people. Studies using functional MRI show a lack of coordination among brain regions, says Marcel Just, director of Carnegie Mellon"s Center for Cognitive Brain Imaging in Pittsburgh, Pa. Just has scanned dozens of 15-to 35-year-old autistic people with IQs in the normal range, giving them thinking tasks as he monitors their brain activity. "One thing you see," says Just, "is that activity in different areas is not going up and down at the same time. There"s a lack of synchronization, sort of like a difference between a jam session and a string quartet. In autism, each area does its own thing."
What remains unclear is whether the interconnectivity problem is the result of autism or its cause. "It"s impossible to tell the chicken from the egg at this point," Just says. Autistic people have been shown to use their brains in unusual ways: they memorize alphabet characters in a part of the brain that ordinarily processes shapes. They tend to use the visual centers in the back of the brain for tasks usually handled by the prefrontal cortex. They often look at the mouth instead of the eyes of someone who is speaking. Their focus, says psychologist Ami Klin of Yale"s Child Study Center, is "not on the social allegiances—for example, the longing gaze of a mother—but physical allegiances—a mouth that moves."

单选题 The best title for the passage is ______.

单选题 Which part is related to human anxiety?

单选题 Which is one of the characteristics of the autistic brain?

单选题 According to Marcel Just, autistic people have been shown to use their brains in unusual ways EXCEPT that ______.

单选题 The underlined "jibes" in Para. 3 means ______.