THE EFFECTS OF LEAD ON OTOACOUSTIC EMISSIONS AND AUDITORY-EVOKED POTENTIALS IN MONKEYS

Auditory functioning was assessed in two groups of adult rhesus monkey s (11 years of age). One (n = 11) received modest exposure to lead ear ly in life and the other (n = 8) served as controls and did not receiv e any lead supplementation. Two lead-exposed monkeys had abnormal dist ortion product otoacoustic emissions (DPEs) and smaller amplitude or a bsent evoked potentials. These monkeys had the highest blood levels re corded in their respective groups. For the remaining lead-exposed monk eys there was little difference between their DPEs and the DPEs of the control monkeys with one exception. DPE amplitudes of the control mon keys increased more rapidly as a function of stimulus level than those of the lead-exposed monkeys at most frequencies. There was also a sig nificant but modest effect of lead exposure on the auditory brain stem evoked responses (ABRs) of these lead-exposed monkeys. There was no a pparent effect on the middle latency evoked responses (MLRs), although that result could be due to the relatively greater variability of the MLR.