Middle Latency Auditory Evoked Potentials in Man

Woods, David

Abstract

During the 60 msec which follow the delivery of auditory signals, neural messages travel from the brainstem to auditory cortex and association areas. Coterminously, a series of electical deflections -- the middle-latency auditory evoked potentials (MAEPs) -- appear over the fronto-central scalp. Due to their great sensitivity to auditory processing of tones across the audiometric spectrum, MAEPs could play an important role in audiological diagnosis. They could also help to clarify the contribution of forebrain systems in normal hearing, and aid in diagnosing structural damage to these systems. However, the utilization of MAEPs remains hampered by a lack of understanding of their fundamental properties. Herein, we propose a series of experiments to clarify their functional properties and neuroanatomical generators, and to elucidate the stimulation and recording procedures necessary for further clinical and research applications. These experiments are designed to answer the following questions: 1) What stimulus features elicit MAEPs? Which MAEP components are produced by stimulus offset, changes in sutmulus frequency, or changes in the apparent spatial position of tones? Which components show binaural interaction? 2) What are the scalp distributions of MAEP components? Do the distributions change with changes in tone frequency and/or ear of stimulus delivery? 3) What are the characteristics of adaptation which occur when stimuli are repeated at very high rates? Do scalp distributions changes during adaptation? 4) What are the auditory processes indexed by different MAEP components? What specificity of adaptation is observed when certain attributes of the stimulus are repeated and others are varied? 5) What are the neuroanatomical generators of the MAEP? How are MAEPs affected by lesions of the neocortex or diencephalon?