Nashville, Tennessee (CNN) -- When Ryan Wallace got a diagnosis of autism at age 2, his parents never thought they'd hear him speak.
"He used to make noises. When he wanted something he would just point," says Ryan's father, Gerald David Wallace. "Or he would scream."
Therapists say that's not unusual for someone with Ryan's condition. According to doctors, many children with autism have difficulty understanding information from the outside world.
"The brain's ability to process information comes in from the eyes, ears and other senses during infancy," says Dr. Mark Wallace, an expert on sensory processing who directs the Vanderbilt Brain Institute who is not related to Ryan."If that [ability] is compromised during the early developmental period, you will never be able to really gain full function in these systems."
Because these children lack the ability to understand this auditory information, it can prevent them from developing any form of language and therefore their ability to communicate. Some stages of autism make it hard for children to comprehend sounds, words, expressions and even inflections.
"That's the thing that parents often notice first in their children [who have autism]. They can't talk," says Dr. Stephen Camarata, a professor of hearing and speech science at Vanderbilt's Wilkerson Center for Otolaryngology and Communication Sciences.
"But the hidden side of this is that they also have a lot of difficulty understanding, comprehending, auditory comprehension, listening. And so when a child's autism is experiencing somebody talking to them, it's a lot like somebody's talking to them in a foreign language," he says.
That can be frustrating for their parents, because at a time when most little ones should be learning to speak, their children can't form words. Many of these parents seek out programs that claim they can help children with autism speak. Doctors warn that can be risky.
"Families who have a child with autism face daunting challenges, says Camarata. "Because of this, they are often going to leave no stone unturned in their searches for solution. Unfortunately, there are a lot of fringe treatments out there, they aren't effective and haven't been scientifically validated."
In the case of Ryan Wallace, now 7, his parents knew at an early age that something was wrong and they needed to intervene.
"He was a healthy baby boy, but then things started to change," says Amy Wallace, Ryan's mom.
"It was around 18 or 20 months we noticed, he was really happy and then he wasn't" according to his dad. "You could see it in his pictures, as he goes from infant into toddlerhood the smile kind of fades away. And then he wouldn't look at you. He would just stare into space. And we had no clue what was going on."
Ryan wouldn't talk. He'd grunt or if he became emotionally upset, he'd have what his parents called "meltdowns" and would start screeching. His parents didn't know what to do or how to handle him. Fortunately, when doctors told them Ryan had autism, they immediately got him into speech and occupational therapy.
"We looked everywhere to find him help," says Amy Wallace. "We finally got him into the Susan Gray School, which is for special-needs kids at Vanderbilt."
While at Susan Gray, Ryan's therapists and parents decided to enroll him in a new research project that was scientifically evaluating programs designed to help kids with autism learn to speak, including sensory integration therapy. Sensory integration is an occupational therapy designed to improve communication skills by placing a child in a room specifically designed to challenge all his or her senses. In the study, Ryan is shown pictures on a computer screen and asked to name and identify the items. The procedure is repeated over and over. He also is given a story that includes all the words he has seen on the computer and at the same time works with a therapist.
"So, children learn how to comprehend through interacting with toys, interacting with pictures, and then an adult or another person is talking to them and giving them information about what they're seeing and experiencing," explains Camarata. "It's very repetitive so that the child has lots of opportunities to learn the meaning of each of these things they're interacting with."
The study is twofold. Once Ryan has gone through his therapy, he's fitted with special headgear that records his brain language sensors while he watches a video that incorporates the words he's just learned. By getting a picture of the brain, it gives doctors an insight into how the autistic brain works.
"The idea is that when you learn a new word you see it and then somebody tells you the name of it and then you link these things in your long-term memory," says Camarata. "People with autism have a very hard time doing that."
Sensory integration therapy advocates say the widely used program's constant stimulation helps children with autism learn to speak. But sensory integration therapy is controversial because there's very little scientific data on its effectiveness. That's why, Camarata says, it's important researchers investigate sensory integration therapy and other therapies to see whether they are effective.
"When these parents are seeking answers," Camarata says, "we as researchers can come to them with answers that have been tested and validated scientifically."
Since Ryan has been working with sensory integration therapy, his parents say, his progress has been remarkable. "He's initiating more. He talks and engages in conversations. He isn't afraid and comes up to people and says, 'Hi!' " Amy Wallace says with a smile. Ryan's father, Gerald, agrees. "That's huge for us. And he says, 'Love you,' and now he says, 'I love you.' You can't ask for more."
The project, which was funded through a two-year, $670,000 federal stimulus grant, is still enrolling children. Sensory integration therapy is just one of many therapies that Camarata, Wallace and their staff hope to investigate in order to prove their worth.
Camarata wants to provide scientifically proven help to families touched by autism.
"I see so many therapies and programs out there that don't work, and they prey on the desperate needs of families. That's wrong," he says. "We are finally starting to get to the point where we can test different interventions and see what works and what doesn't work. If it helps these children, than we need to let parents know. If the therapy doesn't help, than it needs to be exposed for what it is."