ELECTROPHYSIOLOGICAL RESPONSES FROM A TEMPORAL-ORDER CONTINUUM IN THENEWBORN-INFANT

Auditory Evoked Responses (AERs) were used to investigate discriminati on of temporal order differences in eight male and eight female newbor n infants. The temporal lags in two-tone non-speech stimuli-known as t one-onset time (TOT)-modeled the temporal delay of voicing-onset time (VOT), an important cue for voicing contrasts. Analyses on peak amplit ude measures and principal component scores indicated that the amplitu de of the second negative AER deflection (N530) recorded from the left and right parietal leads changed abruptly as TOT values increased fro m + 20 to + 40 msec. However, no differences were noted between tokens that belonged in the same adult perceptual categories. A similar patt ern of variability was observed for the amplitude of the first major n egative peak (N200). Our findings indicate that the neurophysiological mechanisms underlying categorical-like distinctions of a temporal voi cing cue used in speech perception may have an innate basis. Since bot h hemispheres produced similar responses at birth, the present data su ggest that brain mechanisms involved in temporal order processing unde rgo significant reorganization during the first years of life. Copyrig ht (C) 1996 Elsevier Science Ltd.