本文发表于P NATL ACAD SCI USA（刚开始我还以为本杂志是个三流甚至不入流杂志，没想到一查影响因子竟达9.737），作者Minna Huotilainen声称：「新生儿大脑并非一张白纸，实际上他们已经了解了他们父母或者家庭其他成员如何说话的。」
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.
We know that newborn infants can recognize their mother's voice (1), but can they distinguish their mother's voice in the presence of other sound? In general, can neonates organize sounds by their source? Segregating concurrent streams of sound is a crucial moment of sound organization (2), a prerequisite of perceiving objects and, thus, also of forming conceptual objects (3). The processes separating concurrent sound sequences use the temporal behavior of various acoustic parameters, of which spectral pitch is the most effective. In adults, fast presentation of sounds selected from two separated frequency ranges results in an unambiguous perception of two different sound streams, one for the lower- and the other for the higher-pitched sounds (2). Few studies tested whether young (although not newborn) infants can segregate concurrent streams of sound by using behavioral indicators such as the head-turning or the nonnutritive sucking response (4, 5). The results of these studies have suggested that the mechanisms of auditory-stream segregation may be present in young infants.
Our objective test of auditory-stream segregation is based on the fact that the detection of an auditory regularity often depends on how one organizes the incoming sounds. For example, when a familiar melody is interleaved with other sounds, the perception of the original tune is lost. However, if the sounds of the melody are taken from a pitch range that is distinctly different from that of the interleaved sounds, perception of the melody returns (6), because the two sets of sounds are treated as two independent sound sequences (i.e., the two sound streams have been segregated).
To determine whether newborn infants segregate two inter-leaved sound sequences of different frequency ranges, we measured electric brain responses elicited by infrequent deviant tones embedded in the sequence of a repetitive standard tone (the “oddball” sequence; see Fig. 1A, control condition). In this tone sequence, deviants elicit a brain response that is not present in the standard-stimulus response, the mismatch negativity (MMN) event-related brain potential (7). MMN is often followed by another deviation-related electric brain potential, the P3a component (8). These deviation-related brain responses are elicited irrespective of whether the subject performs some task with or ignores the sounds. However, the MMN response is only elicited if the frequent repetition of the standard tone has been detected by the brain. When randomly varying intervening tones are mixed together with the original oddball tone sequence, the intervening tones prevent the brain from detecting the repetition of the standard tone (Fig. 1C, one-stream condition). Therefore it is predicted that the brain responses elicited by the standard and deviant tones will not differ from each other in this condition. Transposing the intervening tones to a frequency range that differs from that of the original tone sequence (Fig. 1E, two-stream condition) while keeping the amount of variation of these tones constant allows the brain to segregate the two sets of tones into separate sound streams. If and only if segregation takes place will the deviation-related brain responses reemerge. Therefore, the elicitation of these brain responses indicates segregation of the original and intervening tones.
This test of auditory-stream segregation, which does not require subjects to perform some task with or report their perception of the sounds, has already been tested successfully in adults (9, 10) and school-age children (11), and the results were found to be fully compatible with the subjects perception of the sound streams (10, 11). Because deviation-related electric brain responses can be measured in newborn and older infants (12–18), auditory-stream segregation could be tested in newborns.