An APD evaluation starts with a comprehensive peripheral hearing evaluation.  I want to make sure that the ear and auditory nerve are working properly and sending complete auditory information to the brain. If there is hearing loss, it needs to be accounted for during the auditory processing testing. A complete peripheral hearing test includes the following:

Pure tone air and bone conduction testing:

This measures the softest sounds you can hear when sound is delivered through the air via headphones and through your bone via a headband.  This is the foundation of a basic audiogram or hearing test. 

Speech in quiet:

This measures your ability to understand speech in a quiet environment.  I am looking at your ability to discriminate speech sounds when no other noise is present. 

Acoustic Reflexes:

The stapedius muscle in the middle ear should contract when a loud sound is heard.  This is called an acoustic reflex and it is your brain's way of protecting your inner ear from loud sounds.  When this muscle is contracted, less sound enters your cochlea.  Measuring acoustic reflexes allows us to look at the integrity of the pathway that the sound takes from the ear to the brainstem and the path from the brainstem back to the ear.      

Otoacoustic Emissions (OAEs):

When sound enters your inner ear (cochlea) the outer hair cells vibrate and generate an electrical signal that travels through the cochlear nerve to the brainstem and up to the cortex.  This hair cell vibration produces a very soft sound that can be measured and it is called an OAE.  When OAEs are present and robust we infer that the hair cells in the cochlea are functioning well.

APD Testing

Seattle Auditory Processing Services primarily uses the Buffalo Model to test for APD, which was developed by Jack Katz, PhD during his time in Buffalo, NY.  This model is very efficient and effective; it uses 3 tests and takes about 45 minutes to complete. The Buffalo model is able to provide up to 30 indicators of APD when the tests are assessed together.  The results will categorize APDs into the 4 categories listed below.  These 4 categories are associated with various sites of lesion.  This classification system helps make sense of the complexity of APD and leads to developing a correct treatment plan.  A thorough diagnosis of APD will lead to an effective treatment plan which makes a world of difference to those with APD!

Decoding:

The ability to quickly and accurately understand speech information.  Can the listener separate words into sounds and can they blend sounds together to form words?  Someone with decoding deficits will have slower processing.  Decoding takes place in the auditory cortex of your brain which is located in the Temporal lobe of the left hemisphere. ‍

Tolerance Fading Memory:

This category refers to 2 skills that are often found together.  Tolerance is the ability to understand speech in the presence of background noise.  Fading memory refers to short term auditory memory, or working memory.  Someone who has working memory deficits will likely have difficulty understanding speech while in the presence of background noise.  These skills take place in the anterior portion of the brain. 

Organization:

The ability to to maintain the proper sequence of information.  People with organizational problems may have reduced spelling skills and difficulty organizing their thoughts and ideas.  They may have difficulty following directions sequentially and they may just be disorganized in general.  The ability to sequence information takes place in the fronto-temporal or frontal-temporal-parietal regions of the brain.‍

Integration:

The ability to bring information together between the right and left brain hemispheres.  This is a challenging category of APD and involves the flow of information from the right hemisphere across the corpus callosum to the left hemisphere. People with an integration deficit may have long response delays or severe reading and spelling difficulties, including dyslexia. The deficit is in the corpus callosum, which is a band of fibers that connects the left and right hemispheres of the brain. 

These categories of APD are not mutually exclusive and most people with APD have deficits in 2 or more categories.  A small percentage of people who struggle with APD will have deficits in all 4 categories.  Someone with a deficit in only one category will experience a mild case of APD and will likely compensate well. Due to the categorization of APD, therapies are effectively targeted to the individual’s unique deficits.