CAPD

Central auditory processing disorders

Because of the extensive bilateral connections of the auditory system,

the only way to have an ipsilateral hearing loss is to have a peripheral lesion i.e., at the cochlea, auditory nerve or cochlear nucleus
bilateral hearing loss from a single lesion is invariably due to a lesion located centrally

N.B. Noise exposure, ototoxic drugs and congenital malformations can cause simultaneous damage bilaterally (considered to be multiple lesions).

central auditory processing involves:
- sound localization and lateralization
- discrimination
- pattern recognition
- the temporal aspects of sounds
- the ability to deal with degraded and competing acoustic signals
  - one classic example of this is the "cocktail party effect". Normally, the central components of the auditory system have little difficulty separating signal from noise (e.g., selectively paying attention to one voice, in a complicated acoustic environment consisting of multiple conversations, sound sources, etc.). However, if components of the central inhibitory pathways are degraded, the person cannot filter out "extra" noise, and therefore cannot hear.
a deficiency in one or more of the above listed behaviors may constitute a Central Auditory Processing Disorder (CAPD)
CAPD occurs when auditory centers of the brain are affected by injury, disease, tumor, heredity or unknown causes
increases in incidence with age
- sensorineural hearing loss tends to synergize with CAPD in the elderly, causing problems regarding hearing aids. Amplification may help combat SNHL, but it can make CAPD worse (think of the cocktail party effect described above; hearing aids amplifying all sounds would make it more difficult to filter unwanted sounds).