What is the difference between APD and CAPD?
The terms APD and CAPD are often used interchangeably. However, the two terms reflect the controversy of whether the auditory processing disorder lies within the central auditory system or results from a breakdown in the entire auditory mechanism. Once the auditory stimulus enters the ear, it transforms from an acoustic signal to a lexical and then a linguistic signal to be interpreted by the brain. This process is a bottom-up process; thus, there is a need for a multimodality function and the involvement of the entire auditory system. Other audiologists restrict the term to the central auditory system only - that is the system beyond the peripheral one since an auditory processing disorder does not involve the outer, middle, or inner ear or the lower brain stem. The position used by ASHA (2005a) is that APD is not a hearing loss, but instead, it is a loss of hearing perception. For this disorder to be totally limited to the central auditory channel is not tenable, neurophysiologically (ASHA, 2005a). Further, a disorder could be due to damage to the auditory nerves from head trauma, complications or middle ear infections, lead poisoning, long-standing OME, and other causes. How auditory processing takes place in the central nervous system is an integrative process and involves several modalities and systems.
This Ask the Expert is an excerpt from the course, 20Q: Auditory Processing - What You Always Wanted to Know