EFFECTS OF LEAD ON AUDITORY SYSTEM IN MONKEYS: HEARING

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OBJECTIVE: To examine auditory system function and attention in the rhesus monkey as a model of childhood lead exposure. Peripheral and higher order auditory processes are evaluated using behavioral and electrophysiological techniques. RESULTS We developed a new behavioral test to assess the effects of previous lead exposure on attention and we continue to test animals in this task. Our studies and others' have demonstrated the effects of early lead exposure on auditory processes in children and in animal models. We evaluated these effects, which occur at multiple levels of the audi-tory system, through behavioral and electrophysiologic techniques. Specific effects on the auditory system likely contribute to the more global cognitive abnormalities associated with childhood lead exposure. These include reduced IQ (especially verbal IQ), attentional deficits, impaired speech per-ception, impaired performance on language production tasks, reading disabilities and school prob-lems. A better understanding of auditory system contributions to the adverse consequences of early lead exposure would facilitate the design of therapeutic interventions and special education programs for children and adults known to have experienced early lead exposure. A broad range of behavioral and physiologic studies will examine auditory system integrity at multiple levels. Behavioral tests will measure absolute and difference thresholds, frequency selectivity, and temporal discriminations, all over a broad range of frequencies. These tasks also evaluate certain attentional processes and func-tions underlying speech and language processing. Physiologic evaluations will provide information on these same fundamental auditory processes. In addition, electrophysiologic studies of the somato-sensory system will evaluate effects of early lead exposure on this important pathway and determine the specificity to the auditory system of lead-induced abnormalities observed previously in the same monkeys. We will also examine the efficacy of phar-macological interventions and procedural changes to attenuate behavioral and physiological effects of lead on auditory processing. Subjects for the proposed studies are 17 adult (15 yr-old) monkeys exposed to lead during early development. We aim to ultimately evaluate enduring and possibly irre-versible effects of early lead exposure. FUTURE DIRECTIONS To clarify effects of lead exposure on attention. KEY WORDS lead, monkeys, hearing, electrophysiological, cognition, auditory processing