What is It? (Hearing vs. Processing)
“Auditory processing”—We are hearing this term be referenced more and more, and an increasing number of children are being identified as having an ” auditory processing disorder.” But what does it actually mean? How can you have normal hearing and have an auditory processing disorder?
First, let’s define “hearing.” The “peripheral hearing mechanism,” as it is referred to, includes the outer ear—where sound waves are collected, the middle ear—where sound is converted to mechanical energy, and the inner ear—containing the cochlea. Traditional hearing tests (audiograms) and tympanograms assess the integrity of this system. If this system is intact and functioning well, then your hearing should test normal.
But what happens when the signal leaves the inner ear? Basically it travels along the auditory nerve, through the brainstem, and eventually reaches the brain. Auditory processing, simply defined, is what happens along this pathway and what the brain does with the auditory signal from the ears. It has a number of different aspects, listed and enumerated differently by different authors. Below we list and define aspects of auditory processing that we have found to be relevant to the children with whom we work. Also listed are additional functions that are closely tied to auditory processing.
Aspects of Auditory Processing
- Auditory attention—being able to “tune in” to auditory input.
- Auditory discrimination—the ability to distinguish between different sounds or words.
- Auditory sequential processing—how many pieces of information one can listen to (receive), store, recall, and utilize. Related to auditory memory. Often tested in terms of digit spans.
- Auditory tonal processing—the correct processing of sounds or tones; related somewhat to auditory discrimination, but takes it a step further; has a significant impact on language processing.
- Auditory memory—ability to store and recall auditory information.
- Auditory sensitivity—perception of sound loudness; hypo-sensitive individuals have a reduced response to sound in their environment, even when hearing is “normal.” Hypersensitive individuals over-respond to “normal” sounds, often perceiving typical environmental sounds as bothersome or too loud.
- Auditory figure-ground processing—ability to attend to and process an auditory stimulus in the presence of background sound.
- Language processing—processing the meaning of verbal input. This is not true auditory processing. It is the next step after auditory processing occurs.
- Temporal processing—related to the “time” aspect of the auditory signal; rate of processing.
Additional Functions Related to Auditory Processing:
- Short-term memory
- Working memory
- Executive function/conceptual thought
- Language development
Factors Affecting Auditory Processing
Hearing—After a number of studies which scientists claimed showed no correlation between ear infections and delayed language development, recent studies have finally confirmed what we have observed all along: the reduction in hearing that is associated with chronic ear fluid or middle ear infections affects how the auditory cortex (that is, the brain) develops. Short-term hearing loss, such as from an ear infection, causes a “weakening” in how the brain learned to process sound. The analogy used was that it is ear-equivalent to a “lazy eye.”
Neurological organization—The organization of the brain determines the efficiency with which the brain carries out its operations. As stated by the terms, the brain is organized or disorganized by degrees. All infants begin life with very disorganized brains, which develop and become organized as a reflection of the input and specific stimulation that the brain receives. The more appropriate and specific the input, the more efficiently the brain/child functions, and the better the neurological organization. This organization, or lack of such, affects all aspects of brain function, including the ability of the brain to process and interpret sound and language.
Developmental issues—Developmental issues, such as Down Syndrome, brain injuries, and autism, to name just a few, impact the brain’s ability to receive and process input to differing and varying degrees. This in turn negatively impacts neurological organization. Any child who has not received the necessary stimulation and opportunities that permit the brain to organize appropriately will remain neurologically disorganized. This will affect function in some significant developmental areas and thus create developmental issues. “Developmental issues” as a category includes problems such as learning disabilities, ADD, ADHD, and dyslexia. Developmental issues affecting the neurological organization can adversely affect the ability of the brain to process and interpret sound and language. Fortunately neuroplasticity is such that at any point in the child’s development TDI-Targeted Developmental Intervention-can reorganize and accelerate the development and organization of the brain.
Sound sensitivity—Both hypo-sensitivity and hyper-sensitivity to sound can have detrimental effects on the developmental of auditory processing skills. For children who have a decreased awareness of sound, they have great difficulty “tuning in” and attending to language. At the opposite extreme, many hyperauditory children tune out in an effort to cope with being overwhelmed by too much auditory input. They also tend to avoid situations and interactions that they know could cause them difficulty.