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BEHAVIORAL
A variety of commercially available behavioral tests measure central auditory nervous system (CANS) function. Various tests assess different levels of function in the CANS and use different protocols. Tests for children and adults are fairly similar in design, but measures for young children have been adapted for language age and mode of responses. For example, one test uses a picture-pointing response format for children with a receptive language of 3 years, and another, for children 6 years of age and older, requires verbatim repetition of sentences.
There are basically three distinct classifications of behavioral tests for central auditory processing (CAP), which involve:
- Presenting different speech stimuli to the two ears at the same time
- Presenting speech or frequency-specific signals to one ear at a time
- Fusing, blending, or sequencing complementary speech stimuli presented to the two ears at different times or with a specified time-onset format
Because a number of CAP tests have been shown to primarily assess specific areas of the CANS, use of a comprehensive test battery is the method of choice for CAP assessment. A battery should include tests shown to be sensitive to several areas of the CANS, including those that target both brainstem and cerebral cortex involvement. Although screening tools have been used as sole indicators of CAPD, their use should be limited to identifying a need for more in-depth CANS assessment.
ELECTROPHYSIOLOGICAL
Although behavioral tests rely chiefly on methods in which recognition of speech stimuli can be made more challenging to the CANS, electrophysiological measures typically use methods by which evoked potential responses are obtained at the brainstem or cortical levels (or both). Electrophysiological tests such as evoked potentials require more time for administration than do more expensive equipment, and more time for administration that do behavioral tests of CAP function. However, current investigations using electrophysiological assessment for CAPD are intriguing as a potential alternative or additional to behavioral measures for identifying CAP inefficiency.
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