What Is Auditory Processing?
Auditory processing is the way your brain makes sense of the sound that it hears. Your ear doesn’t just send whole words up to the brain and instantly understand them. Your ear actually breaks sound up into its fundamental parts – pitch and loudness – and sends those along the auditory nerve up to the brain as it perceives them. And since pitch and loudness change very rapidly in speech, your brain has a lot that it needs to do. It has to recognize each syllable and put all of them back into the right order to create whole words. And it has to attach meaning to the words and sentence. It has to access situational and emotional context to formulate a response. And it has to do all of that very quickly.
You can think of it like playing a real-time game of Wheel Of Fortune but on the order of milliseconds instead of whole minutes. So as you can see, auditory processing is a complex process involving many different skills. And a breakdown in any of those skills can lead to communication problems.
What Structures Are Needed For Auditory Processing?
As I started to describe above, your ear breaks sound down based on pitch and loudness. Because sound is constantly changing, it’s also broken up by time as a function of that presentation. I’m not going to go into the specifics of the parts of the ear and the way it does that because this article is focused on auditory processing specifically. But the important thing to know is that the ear breaks those sounds up as it hears them. It then converts them to a neural signal and sends that signal along the auditory nerve to the brainstem. During these lower-level processes, the nerves enhance the signal a little to aid in understanding. At the brainstem, the two ears also communicate with one another to localize sounds.
Your ears send those signals up through the brainstem to each hemisphere of the brain. There are various other crossings and nuclei involved in signal enhancement as the signal moves up to the cortex. But for the sake of simplicity, let’s discuss in more general terms: the left ear goes to the left hemisphere and the right ear to the right hemisphere. When you have competing noise, the signals prefer to cross (left to right and right to left) in a process called Kimura’s Theory.
Auditory processing relies on each hemisphere to perform specific functions. The right hemisphere listens for patterns in pitch and timing, with cells built and organized for that purpose. The left hemisphere contains Wernicke’s area (where meaning is attached to the speech you hear) and Broca’s area (where your brain plans what you will say). So all the speech you hear has to be filtered through the left hemisphere to produce a response. The two hemispheres communicate with each other across the corpus callosum.
How Do We Test For Auditory Processing Disorders?
We use a series of different tests that look at each of the skills needed to understand speech. Using this battery of tests helps us assess whether a pattern exists so that we can identify a specific auditory processing deficit. That’s necessary because the tests are supposed to be hard, so any person can fail one of the tests and not really have an auditory processing disorder. But if you have trouble with multiple tests that look at the same skill, then there might be a problem. As students of Dr. Jeanane Ferre, We base our approach on the Bellis-Ferre model.
Monaural Low-Redundancy Tests
You’ll hear a recording of a man asking you to repeat some words. Only he’ll sound muffled, like he has his hand over his mouth. This test looks at those skills housed in the left hemisphere of the brain – specifically, can your brain fill in the gaps when you don’t have the full word available? You’ll also hear a recording of a man speaking very quickly and with an echo (time-compressed speech), which looks at the same skills.
You’ll hear a recording of two different sentences, one in each ear, presented at the same time. You’ll ignore the louder one and repeat the softer one. This tells us whether you’re able to separate the sounds heard in each ear independently. This is one aspect of binaural interaction, the way your ears communicate with each other.
You’ll hear a recording of words (numbers or two-syllable words) which will overlap with each other so that you are hearing different things in both ears at the same time. Unlike binaural separation, you’ll have to repeat everything you hear in both ears. Auditory processing relies on binaural integration and interhemispheric transfer to hear in noisy environments in particular. This is the other aspect of binaural interaction (see above).
You’ll hear three sounds which will vary either in pitch or duration and have to repeat the pattern that you hear (ex: “Low, High, Low” or “Short, Short, Long”). This tells us whether you can recognize the pattern in the right hemisphere, transfer it to the left hemisphere, and label it properly. Some people who are unable to complete the labeled task might be able to hum the pattern instead, indicating a problem transferring data between hemispheres.
What Are The Types of Auditory Processing Disorders?
We group auditory processing disorders into two main categories: Primary and Secondary. Primary auditory processing disorders arise from a problem in the central auditory system. Those include Decoding, Integration, and Prosodic deficits. Secondary disorders are an auditory manifestation of some other problem like a language disorder or executive function problem. Those include Associative and Output-Organization deficits.
Primary Auditory Processing Disorders
An Auditory Decoding deficit is a problem in the left hemisphere that makes it difficult to understand words. These are the people who say “What?” all the time, even though they have normal hearing tests. People with this auditory processing issue tend to report difficulty in background noise, mishearing information, and fatigue while listening. They might have slow or inaccurate responses to speech.
An Integration deficit is essentially a problem transferring data between hemispheres. These are people who feel overwhelmed in noise or get easily distracted by other stimuli. It’s characterized by poor manipulation of multiple incoming signals, leading to difficulty in hearing in noise and concentrating on tasks that require the use of both hemispheres. People with this auditory processing issue tend to report problems multitasking or transitioning to new tasks, and understanding verbal information in large chunks.
A Prosodic deficit is a problem in the right hemisphere with detecting patterns. These are people who have difficulty understanding sarcasm and music. It’s characterized by an inability to detect patterns in pitch or timing, leading to difficulty understanding changes in speech pitch and timing to indicate questions or sarcasm. People with this auditory processing issue tend to report they don’t like or understand music, and say they misunderstand the intent of what people say even though they heard all the words correctly.
Secondary Auditory Processing Disorders
An Associative deficit is due to a problem in the left hemisphere either in Broca’s area or in its connection with Wernicke’s area. It’s essentially a problem applying the rules of language. Think of it like a big factory. Your parts come in, they’re put together, everything’s packaged and set on a conveyor belt up to the shipping trucks, and out it goes to the customers. An Associative deficit would be like the conveyor belts breaking down. Things are not getting out properly, and that has a cascading effect which slows everything else down too.
As Output-Organization deficit is likened to an executive function issue. In the same factory analogy, think of what would happen if everything was assembled properly but the labelling system to send the packages out wasn’t working right. Things would end up on the wrong trucks, go out to the wrong customers, and it would be a big mess. Your customers would all think you weren’t paying attention to them, or that you were just too disorganized.
Patient’s with this secondary auditory processing issue tend to report problems formulating and executing responses to what they hear. Planning, direction following, spelling, writing, expressive language, and initializing long tasks might be affected.
How Are Auditory Processing Disorders Treated?
We advocate for the use of both management and intervention when addressing auditory processing issues. Management is the use of behavioral or environmental modifications to minimize the impact of the disorder. Intervention is the use of activities like training techniques to improve the deficient skills. The reason we use the model that we do is that it provides for specific management and intervention tailored to meet the needs of each specific auditory processing deficit profile. For example, children with a decoding deficit sometimes benefit from using hearing aids to improve the acoustic signal. However, you wouldn’t want to give hearing aids to a child with an integration deficit because they have trouble when there’s too much stimulation. Our recommendations for management and intervention are included in a report which you’ll receive after your evaluation, and which can be used by your Speech-Language Pathologist to direct treatment.