Browsing by Author "Pena, Marcela"

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    Investigating the neural correlates of continuous speech computation with frequency-tagged neuroelectric responses
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2009) Buiatti, Marco; Pena, Marcela; Dehaene Lambertz, Ghislaine
    In order to learn an oral language, humans have to discover words from a continuous signal. Streams of artificial monotonous speech can be readily segmented based on the statistical analysis of the syllables' distribution. This parsing is considerably improved when acoustic cues, such as subliminal pauses, are added suggesting that a different mechanism is involved. Here we used a frequency-tagging approach to explore the neural mechanisms underlying word learning while listening to continuous speech. High-density EEG was recorded in adults listening to a concatenation of either random syllables or tri-syllabic artificial words, with or without subliminal pauses added every three syllables. Peaks in the EEG power spectrum at the frequencies of one and three syllables occurrence were used to tag the perception of a monosyllabic or trisyllabic structure, respectively. Word streams elicited the suppression of a one-syllable frequency peak, steadily present during random streams, suggesting that syllables are no more perceived as isolated segments but bounded to adjacent syllables. Crucially, three-syllable frequency peaks were only observed during word streams with pauses, and were positively correlated to the explicit recall of the detected words. This result shows that pauses facilitate a fast, explicit and successful extraction of words from continuous speech, and that the frequency-tagging approach is a powerful tool to track brain responses to different hierarchical units of the speech structure. (C) 2008 Elsevier Inc. All rights reserved.
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    Language acquisition in premature and full-term infants
    (NATL ACAD SCIENCES, 2010) Pena, Marcela; Pittaluga, Enrica; Mehler, Jacques
    We tested healthy preterm (born near 28 +/- 2 weeks of gestational age) and full-term infants at various different ages. We compared the two populations on the development of a language acquisition landmark, namely, the ability to distinguish the native language from a rhythmically similar one. This ability is attained 4 months after birth in healthy full-term infants. We measured the induced gamma-band power associated with passive listening to (i) the infants' native language (Spanish), (ii) a rhythmically close language (Italian), and (iii) a rhythmically distant language (Japanese) as a marker of gains in language discrimination. Preterm and full-term infants were matched for neural maturation and duration of exposure to broadcast speech. We found that both full-term and preterm infants only display a response to native speech near 6 months after their term age. Neural maturation seems to constrain advances in speech discrimination at early stages of language acquisition.
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    Phonological acquisition in preterm infants
    (REVISTA DE NEUROLOGIA, 2010) Pena, Marcela; Pittaluga, Enrica; Farkas, Chamarrita
    Introduction. The stock of phonemes used in the mother tongue is mostly acquired towards the end of the first year of life. Systematic exposure to speech begins, maintains and enhances the learning of native phonemes and lowers sensitivity to non-native ones. Speech deprival gives rise to serious problems in the infant's phonological development, yet little is known about the effects that premature exposure to speech can have on this learning. This study explores this issue by comparing the phonological discrimination of full-term and preterm infants at 12 months of age (corrected age in the preterm infants).
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    Synchronization of neural activity across cortical areas correlates with conscious perception
    (SOC NEUROSCIENCE, 2007) Melloni, Lucia; Molina, Carlos; Pena, Marcela; Torres, David; Singer, Wolf; Rodriguez, Eugenio
    Subliminal stimuli can be deeply processed and activate similar brain areas as consciously perceived stimuli. This raises the question which signatures of neural activity critically differentiate conscious from unconscious processing. Transient synchronization of neural activity has been proposed as a neural correlate of conscious perception. Here we test this proposal by comparing the electrophysiological responses related to the processing of visible and invisible words in a delayed matching to sample task. Both perceived and nonperceived words caused a similar increase of local (gamma) oscillations in the EEG, but only perceived words induced a transient long-distance synchronization of gamma oscillations across widely separated regions of the brain. After this transient period of temporal coordination, the electrographic signatures of conscious and unconscious processes continue to diverge. Only words reported as perceived induced (1) enhanced theta oscillations over frontal regions during the maintenance interval, (2) an increase of the P300 component of the event-related potential, and (3) an increase in power and phase synchrony of gamma oscillations before the anticipated presentation of the test word. We propose that the critical process mediating the access to conscious perception is the early transient global increase of phase synchrony of oscillatory activity in the gamma frequency range.
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    The "soul" of language does not use statistics: Reflections on vowels and consonants
    (ELSEVIER MASSON, CORP OFF, 2006) Mehler, Jacques; Pena, Marcela; Nespor, Marina; Bonatti, Luca
    This paper reviews studies of language processing with the aim of establishing whether any type of statistical information embedded in linguistic signals can be exploited by the language learner. The constraints as to the information that can be so used, we will argue, should be used to inform theories of language acquisition.