Contributions of infant word learning to language development

Infants learn the forms of words by listening to the speech they hear. Though little is known about the degree to which these forms are meaningful for young infants, the words still play a role in early language development. Words guide the infant to his or her first syntactic intuitions, aid in the development of the lexicon, and, it is proposed, may help infants learn phonetic categories.     

Phonetic learning as a pathway to language: new data and native language magnet theory expanded (NLM-e)

Infants' speech perception skills show a dual change towards the end of the first year of life. Not only does non-native speech perception decline, as often shown, but native language speech perception skills show improvement, reflecting a facilitative effect of experience with native language. The mechanism underlying change at this point in development, and the relationship between the change in native and non-native speech perception, is of theoretical interest. As shown in new data presented here, at the cusp of this developmental change, infants' native and non-native phonetic perception skills predict later language ability, but in opposite directions. Better native language skill at 7.5 months of age predicts faster language advancement, whereas better non-native language skill predicts slower advancement. We suggest that native language phonetic performance is indicative of neural commitment to the native language, while non-native phonetic performance reveals uncommitted neural circuitry. This paper has three goals: (i) to review existing models of phonetic perception development, (ii) to present new event-related potential data showing that native and non-native phonetic perception at 7.5 months of age predicts language growth over the next 2 years, and (iii) to describe a revised version of our previous model, the native language magnet model, expanded (NLM-e). NLM-e incorporates five new principles. Specific testable predictions for future research programmes are described.     

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.     

Increased functional connectivity with puberty in the mentalising network involved in social emotion processing

This article is part of a Special Issue “Puberty and Adolescence”.     

Lexical learning and lexical processing in children with developmental language impairments

Lexical skills are a crucial component of language comprehension and production. This paper reviews evidence for lexical-level deficits in children and young people with developmental language impairment (LI). Across a range of tasks, LI is associated with reduced vocabulary knowledge in terms of both breadth and depth and difficulty with learning and retaining new words; evidence is emerging from on-line tasks to suggest that low levels of language skill are associated with differences in lexical competition in spoken word recognition. The role of lexical deficits in understanding the nature of LI is also discussed.     

Examining the Characteristics of Visuospatial Information Processing in Individuals with High-Functioning Autism

Information processing in individuals with autism is marked by a unique interplayof strengths and weaknesses that in concert distinguishes social cognition inautism from individuals with typical-functioning brains. In autism, difficultieswith higher cognitive processing and enhancement of low-level visuospatialprocessing, such as in visual search tasks, may lead to diminished centralcoherence, which has the potential to hinder how an individual functions insocial interactions where integration of components such as intention, emotion,and context paints the global picture necessary for social processing. A morethorough understanding of the cognitive and neural processes in autism isimportant for the advancement of intervention programs. The intention of thisreview is to discuss the implications of neuroimaging and behavioral studiesthat have analyzed the higher cognitive functions in individuals withhigh-functioning autism, with a particular emphasis on studies that haveinvestigated visuospatial processing.     

Social learning of a communicative signal in captive chimpanzees

The acquisition of linguistic competency from more experienced social partners is a fundamental aspect of human language. However, there is little evidence that non-human primates learn to use their vocalizations from social partners. Captive chimpanzees (Pan troglodytes) produce idiosyncratic vocal signals that are used intentionally to capture the attention of a human experimenter. Interestingly, not all apes produce these sounds, and it is unclear what factors explain this difference. We tested the hypothesis that these attention-getting (AG) sounds are socially learned via transmission between mothers and their offspring. We assessed 158 chimpanzees to determine if they produced AG sounds. A significant association was found between mother and offspring sound production. This association was attributable to individuals who were raised by their biological mother-as opposed to those raised by humans in a nursery environment. These data support the hypothesis that social learning plays a role in the acquisition and use of communicative vocal signals in chimpanzees.     

Neurogenomics of speech and language disorders: the road ahead

Next-generation sequencing is set to transform the discovery of genes underlying neurodevelopmental disorders, and so offer important insights into the biological bases of spoken language. Success will depend on functional assessments in neuronal cell lines, animal models and humans themselves.     

Sex-dependent loss of projection neurons involved in avian song learning

In zebra finches, only males sing, and the neural regions controlling song exhibit prominent, hormone-induced sex diffences in neuron number. In order to understand how sexual differentiation regulates neuron number within one song nucleus, the lateral magnocellular nucleus of the anterior neostriatum (IMAN), we studied the development of sex differences among IMAN neurons that project to the robust nucleus of the archistriatum (RA). The IMAN is implicated in song learning, and previous ontogenetic studies have indicated that males lose over 50% of their IMAN neurons during the juvenile song learning period. Based on developmental changes in both the extent of androgen accumulation within the IMAN and its appearance in Nissl-stained tissue, it had been hypothesized that IMAN neuron loss was even greater in young females, resulting in sex differences in neuron number. However, this hypothesis has not been tested directly because the Nissl-stained boundaries of the IMAN sometimes are ambiguous in young animals, and are not evident at all in adult females. To circumvent these problems, we employed the retrograde tracer fast blue to study the development of IMAN neurons defined on the basis of their projections to the RA. We find that the number of these IMAN-RA projection neurons is much greater in adult males than in females, and that this sex difference develops during the juvenile period of sexual differentiation and song learning because a significant number of these neurons are lost in females but not in males. With respect to sexual differentiation, we conclude that masculinization (which is stimulated by the hormone estradiol) promotes the retention of IMAN-RA projection neurons. In addition, our results indicate that any loss of IMAN neurons that may occur in young males does not include cells projecting to the RA. © 1992 John Wiley & Sons, Inc.     

Memory in the making: localized brain activation related to song learning in young songbirds

Songbird males learn to sing their songs from an adult ‘tutor’ early in life, much like human infants learn to speak. Similar to humans, in the songbird brain there are separate neural substrates for vocal production and for auditory memory. In adult songbirds, the caudal pallium, the avian equivalent of the auditory association cortex, has been proposed to contain the neural substrate of tutor song memory, while the song system is involved in song production as well as sensorimotor learning. If this hypothesis is correct, there should be neuronal activation in the caudal pallium, and not in the song system, while the young bird is hearing the tutor song. We found increased song-induced molecular neuronal activation, measured as the expression of an immediate early gene, in the caudal pallium of juvenile zebra finch males that were in the process of learning to sing their songs. No such activation was found in the song system. Molecular neuronal activation was significantly greater in response to tutor song than to novel song or silence in the medial part of the caudomedial nidopallium (NCM). In the caudomedial mesopallium, there was significantly greater molecular neuronal activation in response to tutor song than to silence. In addition, in the NCM there was a significant positive correlation between spontaneous molecular neuronal activation and the strength of song learning during sleep. These results suggest that the caudal pallium contains the neural substrate for tutor song memory, which is activated during sleep when the young bird is in the process of learning its song. The findings provide insight into the formation of auditory memories that guide vocal production learning, a process fundamental for human speech acquisition.     

A computational study of synaptic mechanisms of partial memory transfer in cerebellar vestibulo-ocular-reflex learning

There is a debate regarding whether motor memory is stored in the cerebellar cortex, or the cerebellar nuclei, or both. Memory may be acquired in the cortex and then be transferred to the cerebellar nuclei. Based on a dynamical system modeling with a minimal set of variables, we theoretically investigated possible mechanisms of memory transfer and consolidation in the context of vestibulo-ocular reflex learning. We tested different plasticity rules for synapses in the cerebellar nuclei and took robustness of behavior against parameter variation as the criterion of plausibility of a model variant. In the most plausible scenarios, mossy-fiber nucleus-neuron synapses or Purkinje-cell nucleus-neuron synapses are plastic on a slow time scale and store permanent memory, whose content is passed from the cerebellar cortex storing transient memory. In these scenarios, synaptic strengths are potentiated when the mossy-fiber afferents to the nuclei are active during a pause in Purkinje-cell activities. Furthermore, assuming that mossy fibers create a limited variety of signals compared to parallel fibers, our model shows partial memory transfer from the cortex to the nuclei.     

Use of auditory learning to manage listening problems in children

This paper reviews recent studies that have used adaptive auditory training to address communication problems experienced by some children in their everyday life. It considers the auditory contribution to developmental listening and language problems and the underlying principles of auditory learning that may drive further refinement of auditory learning applications. Following strong claims that language and listening skills in children could be improved by auditory learning, researchers have debated what aspect of training contributed to the improvement and even whether the claimed improvements reflect primarily a retest effect on the skill measures. Key to understanding this research have been more circumscribed studies of the transfer of learning and the use of multiple control groups to examine auditory and non-auditory contributions to the learning. Significant auditory learning can occur during relatively brief periods of training. As children mature, their ability to train improves, but the relation between the duration of training, amount of learning and benefit remains unclear. Individual differences in initial performance and amount of subsequent learning advocate tailoring training to individual learners. The mechanisms of learning remain obscure, especially in children, but it appears that the development of cognitive skills is of at least equal importance to the refinement of sensory processing. Promotion of retention and transfer of learning are major goals for further research.     

Neural mechanisms of infant learning: differences in frontal theta activity during object exploration modulate subsequent object recognition

Investigating learning mechanisms in infancy relies largely on behavioural measures like visual attention, which often fail to predict whether stimuli would be encoded successfully. This study explored EEG activity in the theta frequency band, previously shown to predict successful learning in adults, to directly study infants'' cognitive engagement, beyond visual attention. We tested 11-month-old infants (N = 23) and demonstrated that differences in frontal theta-band oscillations, recorded during infants'' object exploration, predicted differential subsequent recognition of these objects in a preferential-looking test. Given that theta activity is modulated by motivation to learn in adults, these findings set the ground for future investigation into the drivers of infant learning.     

The negative cell cycle regulator, Tob (transducer of ErbB-2), is involved in motor skill learning

Tob (transducer of ErbB-2) is a negative cell cycle regulator with anti-proliferative activity in peripheral tissues. Our previous study identified Tob as a protein involved in hippocampus-dependent memory consolidation (M.L. Jin, X.M. Wang, Y.Y. Tu, X.H. Zhang, X. Gao, N. Guo, Z.Q. Xie, G.P. Zhao, N.H. Jing, B.M. Li, Y.Yu, The negative cell cycle regulator, Tob (Transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory, Neuroscience 131 (2005) 647-659). Here, we provide evidence that Tob in the central nervous system is engaged in acquisition of motor skill. Tob has a relatively high expression in the cerebellum. Tob expression is up-regulated in the cerebellum after rats receive training on a rotarod-running task. Rats infused with Tob antisense oligonucleotides into the 4th ventricle exhibit a severe deficit in running on a rotating rod or walking across a horizontally elevated beam.