A “Bat” Is Easier to Learn than a “Tab”: Effects of Relative Phonotactic Frequency on Infant Word Learning

Many studies have shown that during the first year of life infants start learning the prosodic, phonetic and phonotactic properties of their native language. In parallel, infants start associating sound sequences with semantic representations. However, the question of how these two processes interact remains largely unknown. The current study explores whether (and when) the relative phonotactic probability of a sound sequence in the native language has an impact on infants’ word learning. We exploit the fact that Labial-Coronal (LC) words are more frequent than Coronal-Labial (CL) words in French, and that French-learning infants prefer LC over CL sequences at 10 months of age, to explore the possibility that LC structures might be learned more easily and thus at an earlier age than CL structures. Eye movements of French-learning 14- and 16-month-olds were recorded while they watched animated cartoons in a word learning task. The experiment involved four trials testing LC sequences and four trials testing CL sequences. Our data reveal that 16-month-olds were able to learn the LC and CL words, while14-month-olds were only able to learn the LC words, which are the words with the more frequent phonotactic pattern. The present results provide evidence that infants’ knowledge of their native language phonotactic patterns influences their word learning: Words with a frequent phonotactic structure could be acquired at an earlier age than those with a lower probability. Developmental changes are discussed and integrated with previous findings.     

Precursors to natural grammar learning: preliminary evidence from 4-month-old infants

When learning a new language, grammar--although difficult--is very important, as grammatical rules determine the relations between the words in a sentence. There is evidence that very young infants can detect rules determining the relation between neighbouring syllables in short syllable sequences. A critical feature of all natural languages, however, is that many grammatical rules concern the dependency relation between non-neighbouring words or elements in a sentence i.e. between an auxiliary and verb inflection as in is singing. Thus, the issue of when and how children begin to recognize such non-adjacent dependencies is fundamental to our understanding of language acquisition. Here, we use brain potential measures to demonstrate that the ability to recognize dependencies between non-adjacent elements in a novel natural language is observable by the age of 4 months. Brain responses indicate that 4-month-old German infants discriminate between grammatical and ungrammatical dependencies in auditorily presented Italian sentences after only brief exposure to correct sentences of the same type. As the grammatical dependencies are realized by phonologically distinct syllables the present data most likely reflect phonologically based implicit learning mechanisms which can serve as a precursor to later grammar learning.     

Vocal-auditory functions of the chimpanzee: consonant perception

The perception of consonants which were followed by the vowel [a] was studied in chimpanzees and humans, using a reaction time task in which reaction times for discrimination of syllables were taken as an index of similarity between consonants. Consonants used were 20 natural French consonants and six natural and synthetic Japanese stop consonants. Cluster and MDSCAL analyses of reaction times for discrimination of the French consonants suggested that the manner of articulation is the major determinant of the structure of the perception of consonants by the chimpanzees. Discrimination of stop consonants suggested that the major grouping in the chimpanzees was by voicing. The place of articulation from the lips to the velum was reproduced only in the perception of the synthetic unvoiced stop consonants in the two dimensional MDSCAL space. The phoneme-boundary effect (categorical perception) for the voicing and place-of-articulation features was also examined by a chimpanzee using synthetic [ga]-[ka] and [ba]-[da] continua, respectively. The chimpanzee showed enhanced discriminability at or near the phonetic boundaries between the velar voiced and unvoiced and also between the voiced bilabial and alveolar stops. These results suggest that the basic mechanism for the identification of consonants in chimpanzees is similar to that in humans, although chimpanzees are less accurate than humans in discrimination of consonants.     

The mismatch negativity as an index of the perception of speech sounds by the human brain

The present article outlines the contribution of the mismatch negativity (MMN), and its magnetic equivalent MMNm, to our understanding of the perception of speech sounds in the human brain. MMN data indicate that each sound, both speech and non-speech, develops its neural representation corresponding to the percept of this sound in the neurophysiological substrate of auditory sensory memory. The accuracy of this representation, determining the accuracy of the discrimination between different sounds, can be probed with MMN separately for any auditory feature or stimulus type such as phonemes. Furthermore, MMN data show that the perception of phonemes, and probably also of larger linguistic units (syllables and words), is based on language-specific phonetic traces developed in the posterior part of the left-hemisphere auditory cortex. These traces serve as recognition models for the corresponding speech sounds in listening to speech.     

Effect of bilingualism on lexical stress pattern discrimination in French-learning infants

Monolingual infants start learning the prosodic properties of their native language around 6 to 9 months of age, a fact marked by the development of preferences for predominant prosodic patterns and a decrease in sensitivity to non-native prosodic properties. The present study evaluates the effects of bilingual acquisition on speech perception by exploring how stress pattern perception may differ in French-learning 10-month-olds raised in bilingual as opposed to monolingual environments. Experiment 1 shows that monolinguals can discriminate stress patterns following a long familiarization to one of two patterns, but not after a short familiarization. In Experiment 2, two subgroups of bilingual infants growing up learning both French and another language (varying across infants) in which stress is used lexically were tested under the more difficult short familiarization condition: one with balanced input, and one receiving more input in the language other than French. Discrimination was clearly found for the other-language-dominant subgroup, establishing heightened sensitivity to stress pattern contrasts in these bilinguals as compared to monolinguals. However, the balanced bilinguals' performance was not better than that of monolinguals, establishing an effect of the relative balance of the language input. This pattern of results is compatible with the proposal that sensitivity to prosodic contrasts is maintained or enhanced in a bilingual population compared to a monolingual population in which these contrasts are non-native, provided that this dimension is used in one of the two languages in acquisition, and that infants receive enough input from that language.     

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.     

A locus for an auditory processing deficit and language impairment in an extended pedigree maps to 12p13.31‐q14.3

Despite the apparent robustness of language learning in humans, a large number of children still fail to develop appropriate language skills despite adequate means and opportunity. Most cases of language impairment have a complex etiology, with genetic and environmental influences. In contrast, we describe a three‐generation German family who present with an apparently simple segregation of language impairment. Investigations of the family indicate auditory processing difficulties as a core deficit. Affected members performed poorly on a nonword repetition task and present with communication impairments. The brain activation pattern for syllable duration as measured by event‐related brain potentials showed clear differences between affected family members and controls, with only affected members displaying a late discrimination negativity. In conjunction with psychoacoustic data showing deficiencies in auditory duration discrimination, the present results indicate increased processing demands in discriminating syllables of different duration. This, we argue, forms the cognitive basis of the observed language impairment in this family. Genome‐wide linkage analysis showed a haplotype in the central region of chromosome 12 which reaches the maximum possible logarithm of odds ratio (LOD) score and fully co‐segregates with the language impairment, consistent with an autosomal dominant, fully penetrant mode of inheritance. Whole genome analysis yielded no novel inherited copy number variants strengthening the case for a simple inheritance pattern. Several genes in this region of chromosome 12 which are potentially implicated in language impairment did not contain polymorphisms likely to be the causative mutation, which is as yet unknown.     

Evaluation of Potential Effectors of Agonal Glycolytic Rate in Developing Brain Measured In Vivo by 31P and 1H Nuclear Magnetic Resonance Spectroscopy

Abstract: Previously we have shown that hypercarbia produces a larger decrease in agonal glycolytic rate in 1-month-old swine than in newborns. In an effort to understand the mechanism responsible for this difference, we tested the hypothesis that hypercarbia produces age-related changes in the concentration of one or more effectors of phosphofructokinase activity. Specifically, in vivo ³¹P and ¹H NMR spectroscopy was used to compare changes in lactate levels, intracellular pH, free magnesium concentration, and content of phosphorylated metabolites for these two age groups at three intervals during the first 1.5 min of complete ischemia in the presence or absence of hypercarbia (P_aco ₂ = 102–106 mm Hg). Hypercarbia produced the same drop in intracellular brain pH for both age groups, but the decrease in phosphocreatine level and increase in inorganic phosphate content were greater in 1-month-olds compared with newborns. During ischemia there was no difference between the magnitude of change in intracellular pH and levels of phosphocreatine and inorganic phosphate in hypercarbic 1-month-olds versus newborns. Under control conditions, i.e., normocarbia and normoxia, the free Mg²⁺ concentration was lower and the fraction of magnesium-free ATP was higher for newborns than 1-month-olds. However, there was no change in these variables for either age group during hypercarbia and early during ischemia. Thus, age-related differences in the relative decrease in agonal glycolytic rate during hypercarbia could not be explained by differences in intracellular pH, inorganic phosphate content, or free magnesium concentration. The [ADP]_free at control was higher in newborns compared with 1-month-olds, and there was no age-related difference in [AMP]_free. These variables did not change for newborns when exposed to hypercarbia, but for 1-month-olds [ADP]_free and [AMP]_free increased during hypercarbia relative to control values. High-energy phosphate utilization during ischemia for hypercarbic 1-month-olds was reduced by 74% compared with normocarbic 1-month-olds during ischemia, whereas the reduction in energy utilization (14%) was not significant for hypercarbic versus normocarbic newborns during ischemia. Because hypercarbia reduces the rate of ATP depletion during ischemia in 1-month-olds to a greater extent than in newborns, the increase in [ADP]_free and [AMP]_free will be slower in the former age group. It follows therefore that for 1-month-olds, the agonal glycolytic rate would not be accelerated by ADP and AMP to the same degree during hypercarbia plus ischemia compared with normocarbic plus ischemia, whereas for newborns hypercarbia has relatively little impact on agonal glycolytic rate.     

Bilingual beginnings to learning words

At the macrostructure level of language milestones, language acquisition follows a nearly identical course whether children grow up with one or with two languages. However, at the microstructure level, experimental research is revealing that the same proclivities and learning mechanisms that support language acquisition unfold somewhat differently in bilingual versus monolingual environments. This paper synthesizes recent findings in the area of early bilingualism by focusing on the question of how bilingual infants come to apply their phonetic sensitivities to word learning, as they must to learn minimal pair words (e.g. ‘cat’ and ‘mat’). To this end, the paper reviews antecedent achievements by bilinguals throughout infancy and early childhood in the following areas: language discrimination and separation, speech perception, phonetic and phonotactic development, word recognition, word learning and aspects of conceptual development that underlie word learning. Special consideration is given to the role of language dominance, and to the unique challenges to language acquisition posed by a bilingual environment.     

Connectivity,Not Frequency,Determines the Fate of a Morpheme

Morphemes are the smallest meaningful parts of words and therefore represent a natural unit to study the evolution of words. To analyze the influence of language change on morphemes, we performed a large scale analysis of German and English vocabulary covering the last 200 years. Using a network approach from bioinformatics, we examined the historical dynamics of morphemes, the fixation of new morphemes and the emergence of words containing existing morphemes. We found that these processes are driven mainly by the number of different direct neighbors of a morpheme in words (connectivity, an equivalent to family size or type frequency) and not its frequency of usage (equivalent to token frequency). This contrasts words, whose survival is determined by their frequency of usage. We therefore identified features of morphemes which are not dictated by the statistical properties of words. As morphemes are also relevant for the mental representation of words, this result might enable establishing a link between an individual’s perception of language and historical language change.     

Mechanisms of Reading in Persons with Different Levels of Written Text Comprehension

The aim of the present study was to investigate the reading mechanisms in adults (27 subjects; mean age, 19.5 ± 0.8 [SD] years) with different levels of written text comprehension using fMRI. The main objective was to analyze the basic brain mechanisms of verbal stimuli perception with and without semantic component during reading discrimination tasks. The BOLD signal changes during WORD and PSEUDOWORD reading comparing to GAZE FIXATION state were estimated using both analysis of whole brain activation and ROIs (structures connected with the brain system providing reading) in two groups of subjects, “good” and “poor” readers. It was revealed that activations were higher in “poor” readers in lingual gyrus, SMG, STG compared to “good” readers during PSEUDOWORD reading. It was supposed, that the strategies of words and pseudowords recognition differed in two groups of readers: “good” readers identified words or pseudowords already at the stage of visual analysis of “word” structure and demonstrated attempts to decode pseudowords (i.e., language lexical zones were not activated); “poor” readers, apparently, tried to read pseudowords using the same strategy as for the words reading referring to the lexicon, and after failure identified pseudowords as meaningless concepts. In that case, activations of both lexical “language” zones and visual word form area (VWFA) were observed.     

Utilization of Plasma Fatty Acid in Rat Brain: Distribution of [14C]Palmitate Between Oxidative and Synthetic Pathways

Radioactivity within individual brain compartments was determined from 5 min to 44 h after intravenous injection of [14C]palmitate into awake Fischer-344 rats, aged 21 days or 3 months. Total radioactivity peaked broadly between 15 min and 1 h after injection, declined rapidly between 1 and 2 h, and then more slowly. In 3-month-old rats, the lipid and protein brain fractions were maximally labeled within 15 min after [14C]palmitate injection, then retained approximately constant label for up to 2 days. Radioactivity in the aqueous brain fraction comprised mainly radioactive glutamate and glutamine, and peaked at 45 min, when it comprised 48% of total brain radioactivity, then decreased to 27% of the total at 4 h, 15% at 20 h, and 10% at 44 h. Percent distribution of radioactivity within the different brain compartments, 4 h after intravenous injection of [14C]palmitate, was similar in 21-day-old and 3-month-old rats, despite higher net brain uptake in the younger animals. The results indicate that about 50% of plasma [14C]palmitate that enters the brain of adult rats is incorporated rapidly into stable protein and lipid compartments. The remaining [14C]palmitate enters the aqueous fraction after beta-oxidation, and is slowly lost. At 4 h after injection, 73% of brain radioactivity is within the stable brain compartments; this fraction increases to 86% by 20 h.     

Phonological representations are unconsciously used when processing complex, non-speech signals

Neuroimaging studies of speech processing increasingly rely on artificial speech-like sounds whose perceptual status as speech or non-speech is assigned by simple subjective judgments; brain activation patterns are interpreted according to these status assignments. The naïve perceptual status of one such stimulus, spectrally-rotated speech (not consciously perceived as speech by naïve subjects), was evaluated in discrimination and forced identification experiments. Discrimination of variation in spectrally-rotated syllables in one group of naïve subjects was strongly related to the pattern of similarities in phonological identification of the same stimuli provided by a second, independent group of naïve subjects, suggesting either that (1) naïve rotated syllable perception involves phonetic-like processing, or (2) that perception is solely based on physical acoustic similarity, and similar sounds are provided with similar phonetic identities. Analysis of acoustic (Euclidean distances of center frequency values of formants) and phonetic similarities in the perception of the vowel portions of the rotated syllables revealed that discrimination was significantly and independently influenced by both acoustic and phonological information. We conclude that simple subjective assessments of artificial speech-like sounds can be misleading, as perception of such sounds may initially and unconsciously utilize speech-like, phonological processing.     

Rhythmic processing in children with developmental dyslexia: auditory and motor rhythms link to reading and spelling.

Potential links between the language and motor systems in the brain have long attracted the interest of developmental psychologists. In this paper, we investigate a link often observed (e.g., [Wolff, P.H., 2002. Timing precision and rhythm in developmental dyslexia. Reading and Writing, 15 (1), 179-206.] between motor tapping and written language skills. We measure rhythmic finger tapping (paced by a metronome beat versus unpaced) and motor dexterity, phonological and auditory processing in 10-year old children, some of whom had a diagnosis of developmental dyslexia. We report links between paced motor tapping, auditory rhythmic processing and written language development. Motor dexterity does not explain these relationships. In regression analyses, paced finger tapping explained unique variance in reading and spelling. An interpretation based on the importance of rhythmic timing for both motor skills and language development is proposed.     

Age-dependent changes of nucleic acid labeling in different rat brain regions

The effects of aging on in vivo DNA and RNA labeling and on RNA content in various brain regions of 4-, 12-, and 24-month-old rats were investigated. No difference in [methyl-¹⁴C]thymidine incorporation into DNA of cerebral cortex and cerebelllum during aging was observed.The ratio of RNA/DNA content significantly decreased from 4 to 24 months of age in cerebral cortex, cerebellum and striatum. RNA labeling decreased by 15% in cerebral cortex of 24-month-old animals while in the other brain areas examined (cerebellum, hippocampus, hypothalamus, brainstem, striatum) did not change during aging.In the cerebral cortex, the ratio of the specific radioactivity of microsomal RNA to that of nuclear RNA, determined by in vivo experiments, was not affected by the aging process. A significant decrease of total, poly(A)+ RNA and poly(A)- RNA content was observed in the same brain area of 24-month-old rats compared to 4-month-old ones. Moreover, densitometric and radioactivity patterns obtained by gel electrophoresis of labeled RNA after in vitro experiments (tissue slices of cerebral cortex) showed a different ribosomal RNA processing during aging. In vivo chronic treatment with CDP-choline was able to increase RNA labeling in corpus striatum of 24-month-old animals.     

Vocal-auditory functions in the chimpanzee: Vowel perception

The perception of vowels was studied in chimpanzees and humans, using a reaction time task in which reaction times for discrimination of vowels were taken as an index of similarity between vowels. Vowels used were five synthetic and natural Japanese vowels and eight natural French vowels. The chimpanzees required long reaction times for discrimination of synthetic [i] from [u] and [e] from [o], that is, they need long latencies for discrimination between vowels based on differences in frequency of the second formant. A similar tendency was observed for discrimination of natural [i] from [u]. The human subject required long reaction times for discrimination between vowels along the first formant axis. These differences can be explained by differences in auditory sensitivity between the two species and the motor theory of speech perception. A vowel, which is pronounced by different speakers, has different acoustic properties. However, humans can perceive these speech sounds as the same vowel. The phenomenon of perceptual constancy in speech perception was studied in chimpanzees using natural vowels and a synthetic [o]- [a] continuum. The chimpanzees ignored the difference in the sex of the speakers and showed a capacity for vocal tract normalization.     

Evaluation of 18F-labeled acetylcholinesterase substrates as PET radiotracers

Four 18F-labeled acetylcholinesterase (AChE) substrates, (S)-N-[18F]fluoroethyl-2-piperidinemethyl acetate (1), (R)-N-[18F]fluoroethyl-3-pyrrolidinyl acetate (2), N-[18F]fluoroethyl-4-piperidinyl acetate (3), and (R)-N-[18F]fluoroethyl-3-piperidinyl acetate (4), were evaluated for in vivo blood and brain metabolism in mice, brain pharmacokinetics in rats monkeys (M. nemistrina) using PET imaging. All 18F-labeled compounds were compared to N-[11C]methyl-4-piperidinyl propionate (PMP). Compound 1 was completely metabolized within 1 min in mouse blood and brain. This compound had relatively fast regional brain pharmacokinetics and poor discrimination between brain regions with different AChE concentration. Compound 4 showed relatively slower blood metabolism and slower pharmacokinetics than compound 1 but again poor discrimination between brain regions. Both compounds 1 and 4 showed different kinetic profiles than PMP in PET studies. Compound 3 had the slowest blood metabolism and slower pharmacokinetics than PMP. Compound 2 showed highly encouraging characteristics with an in vivo metabolism rate, primate brain uptake, and regional brain pharmacokinetics similar to [11C]PMP. The apparent hydrolysis rate constant k3 in primate cortex was very close to that of [11C]PMP. This compound has potential to be a good PET radiotracer for measuring brain AChE activity. The longer lifetime of 18F would permit longer imaging times and allows preparation of radiotracer batches for multiple patients and delivery of the tracer to other facilities, making the technique more widely available to clinical investigators.     

NMDA receptor function is enhanced in the hippocampus of aged rats

The density and functional activity of theN-methyl-D-aspartate (NMDA)-sensitive glutamate receptor was examined in various brain areas of 3-, 18- and 24-month-old rats. The total numbers of binding sites for the NMDA receptor antagonists [³H]CGP 39653 and [³H]MK 801 binding sites were decreased in the hippocampus, cerebral cortex and striatum of 18- and 24-month-old rats, relative to 3-month-old animals. In the hippocampus of 18-month-old rats, the reduced number of NMDA receptors was associated with an increased sensitivity of [³H]MK 801 binding to the stimulatory action of glycine and glutamate. Thus, 10 M glycine and 10 M glutamate increased [³H]MK 801 binding in the hippocampus of 18-month-old rats by 75 and 160%, respectively; in 3-month-old animals, the same concentration of these amino acids increased binding by 37 and 95%, respectively. The sensitivity of [³H]MK 801 binding to glycine and glutamate was not increased in the cerebral cortex and striatum of aged rats. Moreover, an increased efficacy of glycine and glutamate in stimulating the binding of [³H]MK 801 in the hippocampus was no longer apparent in the 24-month-old rats. The increased sensitivity of [³H]MK 801 binding to glycine and glutamate in the hippocampus of 18-month-old rats may reflect an increase in NMDA receptor activity to compensate for the decrease in receptor number.     

Effect of Age on Brain Cortical Protein Kinase C and Its Mediation of 5-Hydroxytryptamine Release

The effects of age on the activity and translocation of protein kinase C (PKC) and on the facilitation of 5-hydroxytryptamine (5-HT, serotonin) release induced by PKC activation with the phorbol ester phorbol 12-myristate 13-acetate were investigated. The activities of cortical PKC and its translocation in response to K+ depolarization and phorbol ester stimulation were reduced during aging in Fischer-344 rats. Parietal cortical brain slices from 6-, 12-, and 24-month-old animals were preloaded with [3H]5-HT and release was evoked by 65 mM K+ or the calcium ionophore A23187. 5-HT release induced by either K+ or A23187 was found to be reduced in 12- and 24-month-old as compared to 6-month-old animals. This decrease was not reversed by high extracellular Ca2+. Activation of PKC resulted in a facilitated transmitter release in tissue from 6- and 12-month-old animals but reduced [3H]5-HT release in slices from 24-month-old animals. These responses were prevented by the putative PKC inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), but not by increasing extracellular or intracellular Ca2+. The results demonstrate an age-related change (1) in brain PKC activity and translocation and (2) in a physiological response to PKC stimulation. These results may have implications for other PKC-mediated functions that are altered during senescence.     

Metabolism of Deoxyuridine in Rabbit Brain

Abstract: The metabolism of [³H]deoxyuridine by rabbit brain was investigated in vitro and in vivo . In vitro , brain slices from various regions of brain and from all age groups accumulated [³H]deoxyuridine from artificial CSF. Within the slices, a portion of the accumulated [³H]deoxyuridine was metabolized to [³H]deoxyuridine phosphate, with subsequent conversion to [³H]thymidine phosphate, and ultimately [³H]DNA. The percentage of the [³H]deoxyuridine phosphorylated and subsequently converted into [³H]DNA was highest at birth and declined to adult levels in 3-month-old rabbits. Thymidine, when added to the incubation medium with the [³H]deoxyuridine, was approximately 10 times as potent as unlabeled deoxyuridine in inhibiting the intracellular phosphorylation and conversion of [³H]deoxyuridine to [³H]thymidine phosphate in brain slices. In vivo , 2.5 h after intraventricular injection of [³H]deoxyuridine, over 90% of the [³H]deoxyuridine was cleared from the central nervous system at all ages. However, in both newborn and 3-month-old rabbits, approximately 40 and 12%, respectively, of the ³H remaining in brain was phosphorylated and converted to [³H]thymidine phosphates; and 11 and 4%, respectively, of the ³H remaining in brain was converted to [³H]DNA. These results show that both immature and mature rabbit brain is able to incorporate deoxyuridine into DNA. Thus, all the enzymes involved in this conversion, including thymidylate synthetase (EC 2.1.1.45), are present and active in brain throughout life.