Early tone-evoked responses in normal and hearing-impaired subjects.

Early evoked responses to 500-Hz tone bursts were recorded from normal and hearing-impaired children and adults. The threshold values of the early evoked responses provide useful estimates of auditory functioning, even among difficult-to-test populations, such as deaf-blind children. Latency measures indicate that the early response is generated at the brain stem. Latency measures from hearing-impaired subjects show that the response can identify recruitment. Several subjects having a history of nonspecific communication disorders, e.g., dyslexia, exhibited aberrant early evoked response waveforms. The early-evoked response measures, therefore, amy be useful in detecting and assessing communication disorders which are believed to be of cortical origin, but now should be considered to have a basis in brain stem dysfunction.