Categorical Perception for Voicing Contrasts in Normal and Lead-Treated Rhesus Monkeys: Electrophysiological Indices

摘要

Categorical perception of voicing contrasts was evaluated in rhesus monkeys. The monkeys had been chronically exposed to subclinical levels of lead either from conception to birth, or for approximately six months postnatally beginning at birth, or were never exposed to lead. Auditory evoked responses were recorded at one year of age from scalp electrodes placed over the left and right hemispheres during stimulus presentation. A late component of the brain responses recorded from the right temporal region of all monkeys discriminated between stimuli in a categorical-like manner. The pattern of responses was noted to be similar to that prreviously reported for humans. Categorical discriminations were also noted earlier in the waveforms for control monkeys and for monkeys exposed to lead prenatally. No such effects were noted for monkeys exposed to lead postnatally. These results suggest that the neurocortical mechanisms associated with categorical perception for voicing information may be similar across human and nonhuman primates. However, early exposure to lead appears to alter these processes. (Copyright (c) 1987 by Academic Press, Inc.)