CHARLOTTE, N.C. -- The photos in Dylan Mask's scrapbook show the 4-year-old smiling as he brushes his teeth, sitting stoically as a barber clips his hair. They don't seem particularly unusual, unless you know the story behind them.

A year ago, attempts to cut the Charlotte boy's hair, trim his nails or brush his teeth would send him into crying fits. His coordination was poor. He couldn't differentiate a light touch from a heavy blow. Tap him, and he'd react as if you'd just smacked him.

Dylan is among the growing number of children nationally receiving therapy for sensory integration dysfunction, called DSI, the inability of the brain to correctly process information brought in by the senses.

First described in the 1960s, sensory integration dysfunction and the occupational therapy used to treat it remain controversial. Some doctors and other experts don't believe DSI is a distinct disorder. They say sensory processing difficulties are seen in other disorders, such as autism or attention deficit disorder. Or children with sensory difficulties may just be on the far edge of normal, and they'll eventually learn to cope. Some experts also question whether the therapy works.

But many parents, including Dylan's mom, Lisa Mask, swear by the results.

Children with these difficulties can exhibit a wide variety of symptoms. They might be picky eaters or overly sensitive to sounds. They might be unsure of their body's location in space, so they're clumsy, afraid to ride a bike or attempt activities requiring balance. The same kids overly sensitive to some stimuli might not feel other sensations sufficiently. They could be oblivious to pain, or they might seek out sensation by whirling their body or crashing into things.

To imagine how such children feel, experts suggest you think of a sensory experience that would drive you crazy. The feel of a bug crunching between your teeth, perhaps. Or a blaring television whose volume won't go down. Or the sensation of repeatedly bumping up against people in a packed shopping mall.

Now, imagine those feelings magnified, and constant. "It's like living in a rock concert," says Mask, a grief counselor in Charlotte. "You can't filter out stuff."

Researchers don't know what causes sensory processing difficulties, though many believe these children's brains register sensation differently. The condition affects 5 to 10 percent of U.S. children, estimates Lucy Miller, a professor and occupational therapist who directs the Sensory Integration Dysfunction Treatment and Research Center at The Children's Hospital in Denver.

Experts say they see the condition disproportionately in children who've had birth complications or premature births, who've been abused or deprived of physical contact and children whose parents also have sensory difficulties.

While a link hasn't been proven, some parents, including Mask, attribute their children's difficulties to poisoning from mercury contained in thimerosal, a drug used until recently as a preservative in some childhood vaccines. Dylan may have been exposed to more thimerosal than most children because his mother, who is Rh negative, also received a dose of thimerosal-containing Rhogam while pregnant. The drug is used to protect babies of Rh-negative women from disabilities or death.

DSI was first described at the University of California at Los Angeles by Jean Ayres, an occupational therapist who believed some learning and behavior problems stemmed from the way the children's brains processed sensory information.

Ayres pioneered the sensory integration therapy now widely used by occupational therapists. The treatment involves no drugs. Occupational therapists engage the children in physical activities such as walking a balance beam, climbing up a padded wall, pushing themselves on a scooter board. Parents are also taught to regularly perform sensory activities with their children.

At a recent session at Pathways for Learning -- a pediatric occupational therapy group in Charlotte, which recently opened a small preschool serving children with sensory integration problems - - Dylan swung and spun on a tire swing, an exercise designed to stimulate his vestibular system, which allows the body to regulate focus and coordinate and plan movements. Dylan says the tire swing is his favorite part of therapy. "It's just fun," he says.

Practitioners believe therapy actually changes the brain's neural organization, though they concede more research is needed to prove this. They also agree many children with sensory integration difficulties have other conditions, such as autism. But they say some children have DSI alone.

Critics, however, say there's no evidence the therapy works. Steven Shaw, a psychologist at The Children's Hospital in Greenville, S.C., suspects parents ascribe any improvements to the therapy, when they may have been the result of normal development.

Still, many parents, including Mask, report dramatic therapy results. They say their children are calmer and more focused after a therapy session.

Until Dylan started occupational therapy a year ago, he'd never slept more than a couple hours at a time in his nearly 4 years of life. Within a few weeks of therapy, he was sleeping eight hours straight and now sleeps 11 hours a night. Mask thinks her son couldn't stay asleep because his inability to process his environment kept him in a constant state of "fight or flight."

Colleen Jenny, who organized a support group, Charlotte DSI Parent Connections, about 18 months ago, says sensory integration therapy has also transformed her 5-year-old son, Ryan.

Ryan was so sensitive to sensory stimulation that he couldn't tolerate being in a movie theater, a grocery store, a mall. Today, he attends regular kindergarten. Occupational therapy "is parent- tested," she says. "We come back."

Jenny organized the Charlotte group to provide support and information to parents struggling to understand their children's difficult behaviors, "to say listen, we know what you're talking about about screaming at lights," she says. Some children can't tolerate the sound fluorescent lights make.

"A lot of kids who have sensory integration get kicked out of preschool--boys more than girls," Jenny says. "These are kids that no one wants to baby-sit, no one wants to come over."

Often, teachers or acquaintances have told these parents that their children simply need more discipline. Jenny tries to reassure parents that it's not their parenting that's causing the problems, and that life can eventually return to normal.

Dylan continues therapy for some behaviors, such as his defensiveness to sounds. He still refuses to wear most socks, which he finds "itchy."

But in December, Dylan was able to don a shepherd's costume and participate in his church Christmas play with dozens of other children. To keep sensory stimulation to a manageable level, he wore ear protectors that muffled sounds.

His mother recalls the image of the smiling little shepherd with ear protectors, and tears fill her eyes. "I never thought he'd be able to do that," she says.

Mask says sensory integration may be incorrectly diagnosed sometimes, and sensory integration therapy isn't right for everyone. "But there's a reason for every behavior," she says. "Find the answers for you and your child."

This Article has been submitted by the Jeremy's Prophecy Dot Com team for informational and educational purposes. Jeremy's Prophecy Dot Com is a website dedicated to telling the story of Jeremy Jacobs, a character in the novel, Jeremy's Prophecy Dot Com.