Auditory Processing Disorder
Auditory processing describes the brain’s ability to recognize and interprets surrounding sounds. Humans hear when energy waves that we recognize as sound travels through the ear and is changed into electrical information that can be interpreted by the brain. The "disorder" part of auditory processing disorder (APD) means that something in the brain adversely affects the processing or interpretation of the incoming sound information.
Children with APD often do not recognize subtle differences between sounds in words, even though the sounds themselves are loud and clear. For example, the request "Tell me how a chair and a couch are alike" may sound to a child with APD like "Tell me how a couch and a chair are alike." It can even be understood by the child as "Tell me how a cow and a hair are alike." These kinds of problems are more likely to occur when a person with APD is in a noisy environment, or when he or she is listening to complex information.
APD goes by many other names:
- central auditory processing disorder (CAPD)
- auditory perception problem
- auditory comprehension deficit
- central auditory dysfunction
- central deafness
- and so-called "word deafness"
Children with auditory processing difficulty typically have normal hearing and intelligence. However, they have several signs of APD:
- trouble paying attention to and remembering information presented orally
- problems carrying out multistep directions
- poor listening skills
- Need more time to process information
- low academic performance
- behavior problems
- language difficulty (e.g., they confuse syllable sequences and have problems developing vocabulary and understanding language)
- difficulty with reading, comprehension, spelling, and vocabulary
The cause of APD is unclear. It is thought to be caused by either genes or the environment (such as infections). Human communication relies on taking in complicated perceptual information from the outside world through the senses, such as hearing, and interpreting that information in a meaningful way. Human communication also requires certain mental abilities, such as attention and memory. Scientists still do not understand exactly how all of these processes work and interact, or how they malfunction in cases of communication disorders. Even though a child seems to "hear normally," he or she may have difficulty using those sounds for speech and language.
In children, auditory processing difficulty may be associated with conditions such as dyslexia, attention deficit disorder, autism, autism spectrum disorder, specific language impairment, pervasive developmental disorder, or developmental delay. Sometimes this term has been misapplied to children who have no hearing or language disorder but have challenges in learning.
The parents, a teacher, or a day care provider may be the first person to notice symptoms of APD in a child. Teachers often notice signs of APD based on performance at school. Many health professionals can also diagnose APD in a child. Ongoing observation with these professionals may be necessary.
Much of what these professionals do is to rule out other problems. A pediatrician or a family doctor can help rule out possible diseases that can cause some of these same symptoms. He or she will also measure growth and development. If there is a disease or disorder related to hearing, an affected child may be referred to an otolaryngologist--a physician who specializes in diseases and disorders of the head and neck.
To determine whether a child has a hearing function problem, an audiologic evaluation is necessary. An audiologist gives tests that determine the softest sounds and words a person can hear and other tests that determine the ability to recognize sounds in words and sentences. For example, for one task, the audiologist might have a child listen to different numbers or words in the right and the left ear at the same time. Another common audiologic task involves giving the child two sentences, one louder than the other, at the same time. In these tests, the audiologist is trying to identify the processing problem.
A speech-language pathologist can determine how well a person understands and uses language. A mental health professional can provide information about cognitive and behavioral challenges that may contribute to problems in some cases. Because the audiologist can help with the functional problems of hearing and processing, and the speech-language pathologist is focused on language, they may work as a team.
- genetic counselling
- dopamine level
Much research is still needed to understand APD problems, related disorders, and the best intervention for each child or adult. Several strategies are available to help children with auditory processing difficulties. Some of these are commercially available, but have not been fully studied. Researchers are currently studying a variety of approaches to treatment:
- Auditory trainers are electronic devices that allow a person to focus attention on a speaker and reduce the interference of background noise. They are often used in classrooms, where the teacher wears a microphone to transmit sound and the child wears a headset to receive the sound. Children who wear hearing aids can use them in addition to the auditory trainer.
- Environmental modifications such as classroom acoustics, placement, and seating arrangements may improve auditory processing.
- Exercises to improve language-building skills can increase the ability to learn new words and increase a child's language base.
- Auditory memory enhancement, a procedure that reduces detailed information to a more basic representation, may help. Also, informal auditory training techniques can be used by teachers and therapists to address specific difficulties.
- Auditory integration training may be promoted by practitioners as a way to retrain the auditory system and decrease hearing distortion. However, current research has not proven the benefits of this treatment.
Piracetam may help the patients to some extent.
The prevalence of childhood APD has been estimated at 7%.
In recent years, scientists have developed new ways to study the human brain through imaging. Imaging is a powerful tool that allows the monitoring of brain activity without any surgery. Imaging studies are already giving scientists new insights into auditory processing. Some of these studies are directed at understanding APD. One of the values of imaging is that it provides an objective, measurable view of a process. Many of the symptoms described as related to APD are described differently by different people.
Imaging will help identify the source of these symptoms. Other scientists are studying the central auditory nervous system. Cognitive neuroscientists are helping to describe how the processes that mediate sound recognition and comprehension work in both normal and disordered systems.
- ↑ Bamiou DE, Musiek FE, Luxon LM. Aetiology and clinical presentations of auditory processing disorders. Arch Dis Child. 2001 Nov;85(5):361-5. Abstract