Hemispheric asymmetry of auditory evoked potentials to comparisons within and across phonetic categories

In 10 right-handed Ss, auditory evoked responses (AERs) were recorded from left and right temporal and parietal scalp regions during simple discrimination responses to binaurally presented pairs of synthetic speech sounds ranging perceptually from /ba/ to /da/. A late positive component (P3) in the AER was found to reflect the categorical or phonetic analysis of the stop consonants, with only left scalp sites averaging significantly different responses between acoustic and phonetic comparisons. The result is interpreted as evidence of hemispheric differences in the processing of speech in respect of the level of processing accessed by the particular information processing task.