David M. Gómez

Language universals at birth

Significance It is well known that across languages, certain structures are preferred to others. For example, syllables like blif are preferred to syllables like bdif and lbif. But whether such regularities reflect strictly historical processes, production pressures, or universal linguistic principles is a matter of much debate. To address this question, we examined whether some precursors of these preferences are already present early in life. The brain responses of newborns show that, despite having little to no linguistic experience, they reacted to syllables like blif, bdif, and lbif in a manner consistent with adults’ patterns of preferences. We conjecture that this early—possibly universal—bias helps shaping language acquisition. The evolution of human languages is driven both by primitive biases present in the human sensorimotor systems and by cultural transmission among speakers. However, whether the design of the language faculty is further shaped by linguistic biological biases remains controversial. To address this question, we used near-infrared spectroscopy to examine whether the brain activity of neonates is sensitive to a putatively universal phonological constraint. Across languages, syllables like blif are preferred to both lbif and bdif. Newborn infants (2–5 d old) listening to these three types of syllables displayed distinct hemodynamic responses in temporal-perisylvian areas of their left hemisphere. Moreover, the oxyhemoglobin concentration changes elicited by a syllable type mirrored both the degree of its preference across languages and behavioral linguistic preferences documented experimentally in adulthood. These findings suggest that humans possess early, experience-independent, linguistic biases concerning syllable structure that shape language perception and acquisition.

Memory in the neonate brain

Background The capacity to memorize speech sounds is crucial for language acquisition. Newborn human infants can discriminate phonetic contrasts and extract rhythm, prosodic information, and simple regularities from speech. Yet, there is scarce evidence that infants can recognize common words from the surrounding language before four months of age. Methodology/Principal Findings We studied one hundred and twelve 1-5 day-old infants, using functional near-infrared spectroscopy (fNIRS). We found that newborns tested with a novel bisyllabic word show greater hemodynamic brain response than newborns tested with a familiar bisyllabic word. We showed that newborns recognize the familiar word after two minutes of silence or after hearing music, but not after hearing a different word. Conclusions/Significance The data show that retroactive interference is an important cause of forgetting in the early stages of language acquisition. Moreover, because neonates forget words in the presence of some –but not all– sounds, the results indicate that the interference phenomenon that causes forgetting is selective.

Studying neonates’ language and memory capacities with functional near-infrared spectroscopy

The measurement of newborns’ brain hemodynamic activity has improved our understanding of early cognitive processes, in particular of language acquisition. In this paper, we describe two experimental protocols adapted to study neonates’ speech-processing capacities using functional near-infrared spectroscopy (fNIRS): the block design and the familiarization-recognition design. We review some of their benefits and disadvantages, and refer to research issues that can be explored by means of these protocols. We also illustrate the use of the two experimental designs through representative fNIRS studies that reveal specific patterns of activation of the newborn brain during speech perception, learning of repetition structures, and word recognition.

The word segmentation process as revealed by click detection

The click detection paradigm was once conceived as a method to study online syntactic processing, but well-controlled empirical investigations casted many doubts on the early findings based on it. In this paper, we show that click methods can still prove valid and useful. We asked adult participants to listen to an artificial speech stream composed of statistically defined trisyllabic nonce words, while having to detect clicks superposed on the stream. The clicks were presented either within or between consecutive words. After 2 minutes of exposure to the stream, participants were slower to detect clicks located within words than clicks located between words. This result suggests that methods like click detection are sensitive to online statistical computations, opening new possibilities to obtain a richer picture of the segmentation process than what was hitherto possible.

Long-distance neural synchrony correlates with processing strategies to compare fractions

Adults use different processing strategies to work with fractions. Depending on task requirements, they may analyze the fraction components separately (componential processing strategy, CPS) or consider the fraction as a whole (holistic processing strategy, HPS). It is so far unknown what is the brain coordination dynamics underlying these types of fraction processing strategies. To elucidate this issue, we analyzed oscillatory brain activity during a fraction comparison task, presenting pairs of fractions either with or without common components. Results show that CPS induces a left frontal-parietal alpha phase desynchronization after the onset of fraction pairs, while HPS induces an increase of phase synchrony on theta and gamma bands, over frontal and central-parietal sites, respectively. Additionally, the HPS evokes more negative ERPs around 400 ms over the right frontal scalp than the CPS. This ERP activity correlates with the increase of Theta phase synchrony. Our results reveal the emergence of different functional neural networks depending on the kind of cognitive strategy used for processing fractions.

A critical assessment of the consciousness by synchrony hypothesis.

The understanding of consciousness hasbeen one of the biggest challenges forcognitive science (e.g. Cosmelli et al.,2007; Crick and Koch, 2003; Seth et al.,2006), and the study of the visual systemhas been its theoretical and empiricalstarting point. For instance, theconsciousness by synchrony hypothesispostulates neuronal synchronization as theputative mechanism of visualconsciousness. In this article, we criticizethis idea and the traditional argumentssupporting it. First, we present the relationbetween the consciousness by synchronyhypothesis and the visual binding problem.Then, based on empirical evidence, weanalyze the limitations of neuronalsynchrony to solve both this specificproblem and the more general visualconsciousness issue. We end by consideringa number of additional problems for theconsciousness by synchrony hypothesis.

Brain regions and functional interactions supporting early word recognition in the face of input variability

Significance Since birth, infants begin to learn a myriad of sounds. Yet our knowledge of their abilities to remember specific sounds is primarily based on habituation studies that presented them with massive repetitions of single sounds. The present work opens vistas on the study of language acquisition and memory development by suggesting that the presence of various sounds during encoding does not impair recognition in newborns. Results also indicate that a coordinated interplay between temporal and frontal regions of the brain supports newborns’ ability to memorize specific words in this—previously thought—disruptive context. Perception and cognition in infants have been traditionally investigated using habituation paradigms, assuming that babies’ memories in laboratory contexts are best constructed after numerous repetitions of the very same stimulus in the absence of interference. A crucial, yet open, question regards how babies deal with stimuli experienced in a fashion similar to everyday learning situations—namely, in the presence of interfering stimuli. To address this question, we used functional near-infrared spectroscopy to test 40 healthy newborns on their ability to encode words presented in concomitance with other words. The results evidenced a habituation-like hemodynamic response during encoding in the left-frontal region, which was associated with a progressive decrement of the functional connections between this region and the left-temporal, right-temporal, and right-parietal regions. In a recognition test phase, a characteristic neural signature of recognition recruited first the right-frontal region and subsequently the right-parietal ones. Connections originating from the right-temporal regions to these areas emerged when newborns listened to the familiar word in the test phase. These findings suggest a neural specialization at birth characterized by the lateralization of memory functions: the interplay between temporal and left-frontal regions during encoding and between temporo-parietal and right-frontal regions during recognition of speech sounds. Most critically, the results show that newborns are capable of retaining the sound of specific words despite hearing other stimuli during encoding. Thus, habituation designs that include various items may be as effective for studying early memory as repeated presentation of a single word.

On Two Mechanisms Associated To Learning: A Mathematical Point Of View

We study two important features of the mechanisms living organisms seem to use to solve recurrent problems when able to choose strategies from a known set. The first one is forgetting and its influence on the ability of the organism to learn the chance of success of the known strategies. The other feature is selection of strategies according to their relative strengths. Specifically, we compare exponential and hyperbolic forgetting models, and we prove that when the agent has only one strategy available, the estimates for the strategy success rate using the exponential model never converge (in probabilistic terms), whereas the ones using the hyperbolic model converge almost surely. When more strategies are available and proportional selection is used, we prove several results that generalize the one strategy case.