This study examined the maturation of cortical auditory event-related potentials (ERPs) from birth until 12 months of age. In the 15 infants studied, all ERP peaks observable at 12 months of age, the P150, N250, P350, and N450 were identifiable already at birth, As in previous studies, the amplitudes of the ERP peaks increased and latencies shortened with increasing age. In addition, the time courses of the amplitude growth of these peaks differed from each other. It was concluded, that the generators of all the infantile ERP peaks are functional already at birth, and that the maturational changes in the waveform morphology can mostly be accounted for by the changing relative strengths of the different generators.

Mismatch negativity (MMN) is a negative component of auditory event-related potential (ERP), reflecting the brain's automatic change detection process. In the present study we investigated the development of the pitch change detection, as indexed by the MMN, in the same infants from birth until 12 months of age. The MMN was identified in approximately 75% of infants at each age, being relatively stable in latency and amplitude at the group level across the ages studied. However, within the same subjects the MMN substantially varied from age to age. The inspection of individual data revealed a possible source of this variability: in a portion of 3- to 9-month-old infants, a large-amplitude positive component commenced at the latency of the MMN and thus might have masked it. The results of the additional experiment, employing distracting novel sounds in 2-year-old infants and newborns, suggested that the observed positive component could represent an infant analogue of the adult P3a response, indexing an involuntary orienting of attention. Therefore, the variability from age to age might be, at least partially, caused by the differences in degree of infants' orienting, resulting in the reduction of the scalp recorded mismatch negativity in recordings when the orienting P3a positivity was elicited.

No abstract

The perceptual world of neonates is usually regarded as not yet being fully organized in terms of objects in the same way as it is for adults. Using a recently developed method based on electric brain responses, we found that, similarly to adults, newborn infants segregate concurrent streams of sound, allowing them to organize the auditory input according to the existing sound source. The segregation of concurrent sound streams is a crucial step in the path leading to the identification of objects in the environment. Its presence in newborn infants shows that the basic abilities required for the development of conceptual objects are available already at the time of birth.

audiovisual integration ͉ event-related potentials (ERP) ͉ mismatch negativity (MMN) ͉ speech perception