A complementary systems account of word learning: neural and behavioural evidence

Something old, something new: A review of the literature on sleep-related lexicalization of novel words in adults

Word learning is a crucial aspect of human development that depends on the formation and consolidation of novel memory traces. In this paper, we critically review the behavioural research on sleep-related lexicalization of novel words in healthy young adult speakers. We first describe human memory systems, the processes underlying memory consolidation, then we describe the complementary learning systems account of memory consolidation. We then review behavioural studies focusing on novel word learning and sleep-related lexicalization in monolingual samples, while highlighting their relevance to three main theoretical questions. Finally, we review the few studies that have investigated sleep-related lexicalization in L2 speakers. Overall, while several studies suggest that sleep promotes the gradual transformation of initially labile traces into more stable representations, a growing body of work suggests a rich variety of time courses for novel word lexicalization. Moreover, there is a need for more work on sleep-related lexicalization patterns in varied populations, such as L2 speakers and bilingual speakers, and more work on individual differences, to fully understand the boundary conditions of this phenomenon.

Rapid Cortical Plasticity Induced by Active Associative Learning of Novel Words in Human Adults

Human speech requires that new words are routinely memorized, yet neurocognitive mechanisms of such acquisition of memory remain highly debatable. Major controversy concerns the question whether cortical plasticity related to word learning occurs in neocortical speech-related areas immediately after learning, or neocortical plasticity emerges only on the second day after a prolonged time required for consolidation after learning. The functional spatiotemporal pattern of cortical activity related to such learning also remains largely unknown. In order to address these questions, we examined magnetoencephalographic responses elicited in the cerebral cortex by passive presentations of eight novel pseudowords before and immediately after an operant conditioning task. This associative procedure forced participants to perform an active search for unique meaning of four pseudowords that referred to movements of left and right hands and feet. The other four pseudowords did not require any movement and thus were not associated with any meaning. Familiarization with novel pseudowords led to a bilateral repetition suppression of cortical responses to them; the effect started before or around the uniqueness point and lasted for more than 500 ms. After learning, response amplitude to pseudowords that acquired meaning was greater compared with response amplitude to pseudowords that were not assigned meaning; the effect was significant within 144-362 ms after the uniqueness point, and it was found only in the left hemisphere. Within this time interval, a learning-related selective response initially emerged in cortical areas surrounding the Sylvian fissure: anterior superior temporal sulcus, ventral premotor cortex, the anterior part of intraparietal sulcus and insula. Later within this interval, activation additionally spread to more anterior higher-tier brain regions, and reached the left temporal pole and the triangular part of the left inferior frontal gyrus extending to its orbital part. Altogether, current findings evidence rapid plastic changes in cortical representations of meaningful auditory word-forms occurring almost immediately after learning. Additionally, our results suggest that familiarization resulting from stimulus repetition and semantic acquisition resulting from an active learning procedure have separable effects on cortical activity.

Children's family income is associated with cognitive function and volume of anterior not posterior hippocampus

Children from lower income backgrounds tend to have poorer memory and language abilities than their wealthier peers. It has been proposed that these cognitive gaps reflect the effects of income-related stress on hippocampal structure, but the empirical evidence for this relationship has not been clear. Here, we examine how family income gaps in cognition relate to the anterior hippocampus, given its high sensitivity to stress, versus the posterior hippocampus. We find that anterior (but not posterior) hippocampal volumes positively correlate with family income up to an annual income of ~$75,000. Income-related differences in the anterior (but not posterior) hippocampus also predicted the strength of the gaps in memory and language. These findings add anatomical specificity to current theories by suggesting a stronger relationship between family income and anterior than posterior hippocampal volumes and offer a potential mechanism through which children from different income homes differ cognitively.

Effects of repeated retrieval on keyword mediator use: shifting to direct retrieval predicts better learning outcomes

Keyword mediators are an effective memory technique to encode novel vocabulary: learners link a novel word form to its meaning with a mental image that includes a keyword that resembles the word form (e.g., nyanya = tomato; keyword mnemonic: the ninja chops the tomato in half). Prior research suggests that such mediated form-meaning associations become less dependent on keywords after retrieval practice. The present study investigated if retrieval-induced decreases in mediator use predict word retention. Thirty participants learned novel vocabulary using experimenter-provided keywords and repeatedly retrieved the words from memory while thinking aloud. As expected, keyword use decreased with practice: learners stopped mentioning keywords for 21.6% of the words (on average after 8.27 retrievals). Shifting to direct, unmediated retrieval predicted higher form and meaning recall on a retention test after 6-8 days. Continuing retrieval practice until a shift has occurred to direct retrieval thus seems beneficial for retention.

Is that a pibu or a pibo? Children with reading and language deficits show difficulties in learning and overnight consolidation of phonologically similar pseudowords

Word learning is critical for the development of reading and language comprehension skills. Although previous studies have indicated that word learning is compromised in children with reading disability (RD) or developmental language disorder (DLD), it is less clear how word learning difficulties manifest in children with comorbid RD and DLD. Furthermore, it is unclear whether word learning deficits in RD or DLD include difficulties with offline consolidation of newly learned words. In the current study, we employed an artificial lexicon learning paradigm with an overnight design to investigate how typically developing (TD) children (N = 25), children with only RD (N = 93), and children with both RD and DLD (N = 34) learned and remembered a set of phonologically similar pseudowords. Results showed that compared to TD children, children with RD exhibited: (i) slower growth in discrimination accuracy for cohort item pairs sharing an onset (e.g. pibu‐pibo), but not for rhyming item pairs (e.g. pibu‐dibu); and (ii) lower discrimination accuracy for both cohort and rhyme item pairs on Day 2, even when accounting for differences in Day 1 learning. Moreover, children with comorbid RD and DLD showed learning and retention deficits that extended to unrelated item pairs that were phonologically dissimilar (e.g. pibu‐tupa), suggestive of broader impairments compared to children with only RD. These findings provide insights into the specific learning deficits underlying RD and DLD and motivate future research concerning how children use phonological similarity to guide the organization of new word knowledge.

Better Phonological Short-Term Memory Is Linked to Improved Cortical Memory Representations for Word Forms and Better Word Learning

Language learning relies on both short-term and long-term memory. Phonological short-term memory (pSTM) is thought to play an important role in the learning of novel word forms. However, language learners may differ in their ability to maintain word representations in pSTM during interfering auditory input. We used magnetoencephalography (MEG) to investigate how pSTM capacity in better and poorer pSTM groups is linked to language learning and the maintenance of pseudowords in pSTM. In particular, MEG was recorded while participants maintained pseudowords in pSTM by covert speech rehearsal, and while these brain representations were probed by presenting auditory pseudowords with first or third syllables matching or mismatching the rehearsed item. A control condition included identical stimuli but no rehearsal. Differences in response strength between matching and mismatching syllables were interpreted as the phonological mapping negativity (PMN). While PMN for the first syllable was found in both groups, it was observed for the third syllable only in the group with better pSTM. This suggests that individuals with better pSTM maintained representations of trisyllabic pseudowords more accurately during interference than individuals with poorer pSTM. Importantly, the group with better pSTM learned words faster in a paired-associate word learning task, linking the PMN findings to language learning.

Procedural and declarative memory brain systems in developmental language disorder (DLD)

The aim of the current study was to examine microstructural differences in white matter relevant to procedural and declarative memory between adolescents/young adults with and without Developmental Language Disorder (DLD) using diffusion tensor imaging (DTI). The findings showed atypical age-related changes in white matter structures in the corticostriatal system, in the corticocerebellar system, and in the medial temporal region in individuals with DLD. Results highlight the importance of considering the age factor in research on DLD. Future studies are needed to examine the developmental relationship between long-term memory and individual differences in language development and learning.

The Structure of Word Learning in Young School-Age Children

Purpose We investigated four theoretically based latent variable models of word learning in young school-age children. Method One hundred sixty-seven English-speaking second graders with typical development from three U.S. states participated. They completed five different tasks designed to assess children's creation, storage, retrieval, and production of the phonological and semantic representations of novel words and their ability to link those representations. The tasks encompassed the triggering and configuration stages of word learning. Results Results showed that a latent variable model with separate phonological and semantic factors and linking indicators constrained to load on the phonological factor best fit the data. Discussion The structure of word learning during triggering and configuration reflects separate but related phonological and semantic factors. We did not find evidence for a unidimensional latent variable model of word learning or for separate receptive and expressive word learning factors. In future studies, it will be interesting to determine whether the structure of word learning differs during the engagement stage of word learning when phonological and semantic representations, as well as the links between them, are sufficiently strong to affect other words in the lexicon.

Diferencias temporales y espaciales en el procesamiento de incongruencias léxicas: un estudio de potenciales relacionados a eventos

Introducción. La comprensión del lenguaje está determinada por diversos procesos, entre los que se encuentra el reconocimiento léxico. Según el modelo conexionista, este reconocimiento se genera por activación mediante el emparejamiento de la información acumulada y por la inhibición de las entradas léxicas que compiten por activación.Objetivo. Determinar las diferencias temporales y espaciales de procesamiento entre las incongruencias léxicas semánticamente relacionadas a un contexto lingüístico oracional y las no relacionadas.Materiales y métodos. Se realizó medición de los potenciales relacionados a eventos en 10 sujetos sanos por medio de un paradigma de 240 oraciones en español agrupadas de la siguiente manera: 80 oraciones congruentes, 80 con incongruencias dentro del campo léxico y 80 con incongruencias fuera del campo léxico.Resultados. Se observó una diferencia estadística en la latencia de aparición del componente N400 entre las dos condiciones. Por su parte, se encontró una mayor activación del precúneo, del giro orbitofrontal, del giro angular y del giro supramarginal en la condición de incongruencia fuera del campo léxico.Conclusión. Se encontraron diferencias temporales y espaciales (activación del precúneo, del giro orbitofrontal, del giro angular y del giro supramarginal) entre el procesamiento de las incongruencias léxicas y no léxicas.

Word learning reveals white matter plasticity in preschool children

Word learning plays a central role in language development and is a key predictor for later academic success. The underlying neural basis of successful word learning in children is still unknown. Here, we took advantage of the opportunity afforded by diffusion-weighted magnetic resonance imaging to investigate neural plasticity in the white matter of typically developing preschool children as they learn words. We demonstrate that after 3 weeks of word learning, children showed significantly larger increases of fractional anisotropy (FA) in the left precentral white matter compared to two control groups. Average training accuracy was correlated with FA change in the white matter underlying the left dorsal postcentral gyrus, with children who learned more slowly showing larger FA increases in this region. Moreover, we found that the status of white matter in the left middle temporal gyrus, assumed to support semantic processes, is predictive for early stages of word learning. Our findings provide the first evidence for white matter plasticity following word learning in preschool children. The present results on learning novel words in children point to a key involvement of the left fronto-parietal fiber connection, known to be implicated in top-down attention as well as working memory. While working memory and attention have been discussed to participate in word learning in children, our training study provides evidence that the neural structure supporting these cognitive processes plays a direct role in word learning.

Growing up with interfering neighbours: the influence of time of learning and vocabulary knowledge on written word learning in children

Evidence suggests that new vocabulary undergoes a period of strengthening and integration offline, particularly during sleep. Practical questions remain, however, including whether learning closer to bedtime can optimize consolidation, and whether such an effect varies with vocabulary ability. To examine this, children aged 8-12-years-old (n 59) were trained on written novel forms (e.g. BANARA) in either the morning (long delay) or the evening (short delay). Immediately after training and the next day, lexical competition (a marker of integration) was assessed via speeded semantic decisions to neighbouring existing words (e.g. BANANA); explicit memory was measured via recognition and recall tasks. There were no main effects indicating performance changes across sleep for any task, counter to studies of spoken word learning. However, a significant interaction was found, such that children with poorer vocabulary showed stronger lexical competition on the day after learning if there was a short delay between learning and sleep. Furthermore, while poorer vocabulary was associated with slower novel word recognition speed before and after sleep for the long delay group, this association was only present before sleep for the short delay group. Thus, weak vocabulary knowledge compromises novel word acquisition, and when there is a longer period of post-learning wake, this disadvantage remains after a consolidation opportunity. However, when sleep occurs soon after learning, consolidation processes can compensate for weaker encoding and permit lexical integration. These data provide preliminary suggestion that children with poorer vocabulary may benefit from learning new words closer to bedtime.

Neuroimaging the sleeping brain: Insight on memory functioning in infants and toddlers

Episodic memory, or the ability to remember past events with specific detail, is central to the human experience and is related to learning and adaptive functioning in a variety of domains. In typically developing children, episodic memory emerges during infancy and improves during early childhood and beyond. Developmental processes within the hippocampus are hypothesized to be primarily responsible for both the early emergence and persistence of episodic memory in late infancy and early childhood. However, these hypotheses are based on non-human models. In-vivo investigations in early human development of hippocampal processes have been significantly limited by methodological challenges in acquiring neuroimaging data, particularly task-related functional neuroimaging data, from infants and toddlers. Recent studies in adults have shown neural activity in the brain regions supporting episodic memory during slow-wave sleep using functional magnetic resonance imaging (fMRI), and fMRI has been increasingly utilized in infancy and early childhood to address other research questions. We review initial evidence and present preliminary data showing the promise of this approach for examining hippocampal contribution to how infants and toddlers remember individual events, and their association with information about the context in which the event occurred. Overall, our review, integrated with the presentation of some preliminary data provides insight on leveraging sleep to gain new perspectives on early memory functioning.

Semantic Memory and the Hippocampus: Revisiting, Reaffirming, and Extending the Reach of Their Critical Relationship

Since Tulving proposed a distinction in memory between semantic and episodic memory, considerable effort has been directed towards understanding their similar and unique features. Of particular interest has been the extent to which semantic and episodic memory have a shared dependence on the hippocampus. In contrast to the definitive evidence for the link between hippocampus and episodic memory, the role of the hippocampus in semantic memory has been a topic of considerable debate. This debate stems, in part, from highly variable reports of new semantic memory learning in amnesia ranging from profound impairment to full preservation, and various degrees of deficit and ability in between. More recently, a number of significant advances in experimental methods have occurred, alongside new provocative data on the role of the hippocampus in semantic memory, making this an ideal moment to revisit this debate, to re-evaluate data, methods, and theories, and to synthesize new findings. In line with these advances, this review has two primary goals. First, we provide a historical lens with which to reevaluate and contextualize the literature on semantic memory and the hippocampus. The second goal of this review is to provide a synthesis of new findings on the role of the hippocampus and semantic memory. With the perspective of time and this critical review, we arrive at the interpretation that the hippocampus does indeed make necessary contributions to semantic memory. We argue that semantic memory, like episodic memory, is a highly flexible, (re)constructive, relational and multimodal system, and that there is value in developing methods and materials that fully capture this depth and richness to facilitate comparisons to episodic memory. Such efforts will be critical in addressing questions regarding the cognitive and neural (inter)dependencies among forms of memory, and the role that these forms of memory play in support of cognition more broadly. Such efforts also promise to advance our understanding of how words, concepts, and meaning, as well as episodes and events, are instantiated and maintained in memory and will yield new insights into our two most quintessentially human abilities: memory and language.

Settling Into Semantic Space: An Ambiguity-Focused Account of Word-Meaning Access

Most words are ambiguous: Individual word forms (e.g., run) can map onto multiple different interpretations depending on their sentence context (e.g., the athlete/politician/river runs). Models of word-meaning access must therefore explain how listeners and readers can rapidly settle on a single, contextually appropriate meaning for each word that they encounter. I present a new account of word-meaning access that places semantic disambiguation at its core and integrates evidence from a wide variety of experimental approaches to explain this key aspect of language comprehension. The model has three key characteristics. (a) Lexical-semantic knowledge is viewed as a high-dimensional space; familiar word meanings correspond to stable states within this lexical-semantic space. (b) Multiple linguistic and paralinguistic cues can influence the settling process by which the system resolves on one of these familiar meanings. (c) Learning mechanisms play a vital role in facilitating rapid word-meaning access by shaping and maintaining high-quality lexical-semantic knowledge throughout the life span. In contrast to earlier models of word-meaning access, I highlight individual differences in lexical-semantic knowledge: Each person's lexicon is uniquely structured by specific, idiosyncratic linguistic experiences.

The Neurocognition of Developmental Disorders of Language

Developmental disorders of language include developmental language disorder, dyslexia, and motor-speech disorders such as articulation disorder and stuttering. These disorders have generally been explained by accounts that focus on their behavioral rather than neural characteristics; their processing rather than learning impairments; and each disorder separately rather than together, despite their commonalities and comorbidities. Here we update and review a unifying neurocognitive account—the Procedural circuit Deficit Hypothesis (PDH). The PDH posits that abnormalities of brain structures underlying procedural memory (learning and memory that rely on the basal ganglia and associated circuitry) can explain numerous brain and behavioral characteristics across learning and processing, in multiple disorders, including both commonalities and differences. We describe procedural memory, examine its role in various aspects of language, and then present the PDH and relevant evidence across language-related disorders. The PDH has substantial explanatory power, and both basic research and translational implications.

WORD LEARNING IN APHASIA: TREATMENT IMPLICATIONS AND STRUCTURAL CONNECTIVITY ANALYSES

OBJECTIVE

Of current interest in aphasia research is the relevance of what we can learn from studying word learning ability in aphasia. In a preliminary study, we addressed two issues related to the novel word learning ability of individuals with aphasia. First, as word learning engages large-scale cognitive-linguistic systems (language skills, verbal short-term memory (STM), other memory and executive functions), we probed whether novel word learning practice in three people with aphasia could stimulate these language-related systems. Second, as lesion correlates affecting word learning in aphasia remain unclear, we examined whether the structural integrity of the left arcuate fasciculus (AF) in the same three individuals is related to outcomes of novel word learning practice.

METHOD

To stimulate word learning systems, our three participants practiced for 4 weeks with an explicit novel word - novel referent word learning task, adopted from the Ancient Farming Equipment learning paradigm (Laine & Salmelin, 2010). The participants' progress on receptive and expressive novel word learning was followed up, and their language and verbal STM abilities as well as single-session novel word learning (Learning to Name Aliens by Gupta, Martin, Abbs, Schwartz & Lipinski, 2006) were tested before and after the practice period. To address the second question, we analyzed the participants' structural MRI scans with respect to the integrity of the left AF and its overlap with the lesion areas.

RESULTS

All participants showed some receptive word learning in the trained task, as well as improvements in verbal STM span at posttest. Two of the three participants also showed improved performance on some of the language outcome measures. One participant with partially spared left AF, especially temporo-parietal connections, exhibited better word learning performance than the other two who had larger damage and disconnection of the AF.

CONCLUSIONS

While the present results are preliminary, they open the possibility that novel word learning practice in aphasia may stimulate remaining word learning mechanisms in aphasia, and thereby influence language and verbal STM abilities. These results also suggest that preservation of novel word learning ability in aphasia in part depends on the integrity of the left arcuate track.

Quick reorganization of memory traces for morphologically complex words in young children

Formation of neural mechanisms for morphosyntactic processing in young children is still poorly understood. Here, we addressed neural processing and rapid online acquisition of familiar and unfamiliar combinations of morphemes. Three different types of morphologically complex words - derived, inflected, and novel (pseudostem + real suffix) - were presented in a passive listening setting to 16 typically developing 3-4-year old children (as part of a longitudinal Helsinki SLI follow-up study). The mismatch negativity (MMN) component of event-related potentials (ERP), an established index of long-term linguistic memory traces in the brain, was analysed separately for the initial and final periods of the exposure to these items. We found MMN response enhancement for the inflected words towards the end of the recording session, whereas no response change was observed for the derived or novel complex forms. This enhancement indicates rapid build-up of a new memory trace for the combination of real morphemes, suggesting a capacity for online formation of whole-form lexicalized representations as one of the morphological mechanisms in the developing brain. Furthermore, this enhancement increased with age, suggesting the development of automatic morphological processing circuits in the age range of 3-4 years.

The effect of overnight consolidation in the perceptual learning of non-native tonal contrasts

Sleep-mediated overnight consolidation has been found to facilitate perceptual learning by promoting learners’ generalization across talkers in their perception of novel segmental categories. Lexical tone is characterized by high variability across talkers, and displays dynamic change over time. For this reason, it remains unclear whether a similar effect of overnight consolidation would be found for perceptual learning of novel tonal contrasts. Thus, this study aims to examine whether overnight consolidation facilitates talker-independent learning of lexical tones in the identification and discrimination of novel Cantonese level tones by Mandarin listeners. Two groups of Mandarin listeners were perceptually trained either in the morning or in the evening. Listeners were trained in a tone identification (ID) task with feedback using stimuli produced by a trained talker. Their post-training changes and generalization to a novel talker were then tested in the ID and AX discrimination tasks using stimuli produced by trained and untrained talkers in three posttests following training: immediately after training, 12-hour delay, and 24-hour delay. While the evening group slept between the first and second posttests, the morning group did not. The accuracy rates in the ID task showed that the evening group showed an improved trend, predicted by their individual sleep time, in identifying the level tones produced by both the trained and untrained talkers; in contrast, the morning group showed a declining trend. The d-prime scores in the AX discrimination task did not show different patterns between the two groups. The finding of sleep-related identification changes over time suggests that overnight consolidation might have facilitated tone learning of stimuli produced by the novel talker and eventually facilitated the formation of a more talker-independent representation of novel tone categories in long-term memory. The results are discussed in light of the features of lexical tones to shed light on the mechanism of phonetic learning.

Learning of novel compound nouns - A variant of lexical learning that requires intact verbal short-term memory

Verbal short-term memory (vSTM) plays a crucial role in word learning, and patients with impaired vSTM have been demonstrated to fail on learning novel word forms. Word learning has exclusively been investigated with previously unknown or pseudowords. Several languages, however, make use of composition, i.e., combining morphemes into compounds. On the one hand, this is comparable to pseudoword learning because known elements are combined into novel representations, on the other hand compounds differ from pseudowords learning because they consist of previously known (lexical) elements. This may help to identify the role of vSTM in word learning. The present paper documents impaired word learning in a participant with impaired vSTM but also assessed, for the first time, the acquisition of novel noun-noun compounds. In two independent experiments, the participant was impaired in learning nonsense compounds ("ball door") and the names of previously unknown tools ("nail puller"; "drill bit"). Control experiments revealed her impairment of word learning and novel compound noun learning to be selective: IS could acquire information about the novel tools' function and purpose and was unimpaired in several experiments on paired associate learning including different stimuli. The results suggest that vSTM is involved in variants of lexical learning such as compound noun acquisition. Implications for the modeling of the relationship between vSTM and word learning are discussed.

Neural Patterns in Linguistic Cortices Discriminate the Content of Verbal Working Memory

An influential theoretical account of working memory (WM) considers that WM is based on direct activation of long-term memory knowledge. While there is empirical support for this position in the visual WM domain, direct evidence is scarce in the verbal WM domain. This question is critical for models of verbal WM, as the question of whether short-term maintenance of verbal information relies on direct activation within the long-term linguistic knowledge base or not is still debated. In this study, we examined the extent to which short-term maintenance of lexico-semantic knowledge relies on neural activation patterns in linguistic cortices, and this by using a fast encoding running span task for word and nonword stimuli minimizing strategic encoding mechanisms. Multivariate analyses showed specific neural patterns for the encoding and maintenance of word versus nonword stimuli. These patterns were not detectable anymore when participants were instructed to stop maintaining the memoranda. The patterns involved specific regions within the dorsal and ventral pathways, which are considered to support phonological and semantic processing to various degrees. This study provides novel evidence for a role of linguistic cortices in the representation of long-term memory linguistic knowledge during WM processing.

Atypicalities in sleep and semantic consolidation in autism

Sleep is known to support the neocortical consolidation of declarative memory, including the acquisition of new language. Autism spectrum disorder (ASD) is often characterized by both sleep and language learning difficulties, but few studies have explored a potential connection between the two. Here, 54 children with and without ASD (matched on age, nonverbal ability and vocabulary) were taught nine rare animal names (e.g., pipa). Memory was assessed via definitions, naming and speeded semantic decision tasks immediately after learning (pre‐sleep), the next day (post‐sleep, with a night of polysomnography between pre‐ and post‐sleep tests) and roughly 1 month later (follow‐up). Both groups showed comparable performance at pre‐test and similar levels of overnight change on all tasks; but at follow‐up children with ASD showed significantly greater forgetting of the unique features of the new animals (e.g., pipa is a flat frog). Children with ASD had significantly lower central non‐rapid eye movement (NREM) sigma power. Associations between spindle properties and overnight changes in speeded semantic decisions differed by group. For the TD group, spindle duration predicted overnight changes in responses to novel animals but not familiar animals, reinforcing a role for sleep in the stabilization of new semantic knowledge. For the ASD group, sigma power and spindle duration were associated with improvements in responses to novel and particularly familiar animals, perhaps reflecting more general sleep‐associated improvements in task performance. Plausibly, microstructural sleep atypicalities in children with ASD and differences in how information is prioritized for consolidation may lead to cumulative consolidation difficulties, compromising the quality of newly formed semantic representations in long‐term memory.

Constraints on learning disjunctive, unidimensional auditory and phonetic categories

Phonetic categories must be learned, but the processes that allow that learning to unfold are still under debate. The current study investigates constraints on the structure of categories that can be learned and whether these constraints are speech-specific. Category structure constraints are a key difference between theories of category learning, which can roughly be divided into instance-based learning (i.e., exemplar only) and abstractionist learning (i.e., at least partly rule-based or prototype-based) theories. Abstractionist theories can relatively easily accommodate constraints on the structure of categories that can be learned, whereas instance-based theories cannot easily include such constraints. The current study included three groups to investigate these possible constraints as well as their speech specificity: English speakers learning German speech categories, German speakers learning German speech categories, and English speakers learning musical instrument categories, with each group including participants who learned different sets of categories. Both speech groups had greater difficulty learning disjunctive categories (ones that require an "or" statement) than nondisjunctive categories, which suggests that instance-based learning alone is insufficient to explain the learning of the participants learning phonetic categories. This fact was true for both novices (English speakers) and experts (German speakers), which implies that expertise with the materials used cannot explain the patterns observed. However, the same was not true for the musical instrument categories, suggesting a degree of domain-specificity in these constraints that cannot be explained through recourse to expertise alone.

Prior Knowledge Predicts Early Consolidation in Second Language Learning

Language learning occurs in distinct phases. Whereas some improvement is evident during training, offline memory consolidation processes that take place after the end of training play an important role in learning of linguistic information. The timing of offline consolidation is thought to depend on the type of task, with generalization of implicit knowledge suggested to take more time and sleep to consolidate. The current study aims to investigate individual differences in the timing of consolidation following learning of morphological inflections in a novel language in typical adults. Participants learned to make plural inflections in an artificial language, where inflection was based on morpho-phonological regularities. Participants were trained in the evening, and consolidation was measured after two intervals: 12 h (one night) and 36 h (two nights) post training. We measured both inflection of trained items, which may rely on item-specific learning, and generalization to new untrained items, which requires extraction of morpho-phonological regularities. The results for both trained and un-trained items showed two patterns of consolidation: early versus late, that is while some participants improved during the first night, others, who deteriorated in performance during the first night, improved in the later consolidation interval. Importantly, phonological awareness in L1 predicted early consolidation for trained items. Furthermore, there was no association between participants' consolidation trajectory in trained and untrained items. Our results suggest that consolidation timing depends on the interaction between task characteristics and individual abilities. Moreover, the results show that prior meta-linguistic knowledge predicts the quality of early consolidation processes. These results are consistent with studies in rodents and humans, showing that prior knowledge accelerates consolidation of newly learnt episodic memory. Finally, the rate of consolidation across exposures to the language might explain some of the variability found in the attained level of second language proficiency.

Age of acquisition impacts the brain differently depending on neuroanatomical metric

Although researchers generally agree that a certain set of brain areas underlie bilingual language processing, there is discrepancy regarding what effect timing of language acquisition has on these regions. We aimed to investigate the neuroanatomical correlates of age of acquisition (AoA), which has been examined previously, but with inconsistent results, likely influenced by methodological differences across studies. We analyzed gray matter density, volume, and thickness using whole-brain linear models in 334 bilinguals and monolinguals. Neuroanatomical correlates of AoA differed depending on gray matter metric. Relative to early bilinguals, late bilinguals had thicker cortex in language processing and cognitive control regions, and greater density in multiple frontal areas and the right middle temporal and supramarginal gyri. Early bilinguals had greater volume than late bilinguals in the left middle temporal gyrus. Overall, volume was the least sensitive to AoA-related differences. Multiple regions not classically implicated in dual-language processing were also found, which highlights the important role of whole-brain analyses in neuroscience. This is the first study to investigate AoA and gray matter thickness, volume, and density all in the same sample. We conclude that cognitive models of bilingualism should consider the roles of development and neuroanatomical metric in driving our understanding of bilingual and monolingual language organization.

The Impact of Dose and Dose Frequency on Word Learning by Kindergarten Children With Developmental Language Disorder During Interactive Book Reading

Purpose

The goal was to determine whether interactive book reading outcomes for children with developmental language disorder (DLD) were affected by manipulation of dose (i.e., the number of exposures to the target word during a book reading session) and dose frequency (i.e., the number of repeated book reading sessions) and whether pretreatment factors predicted treatment response variation.

Method

Thirty-four kindergarten children with DLD (aged 5;0–6;2 [years;months]) were taught 1 set of words using the Dose 6 and Dose Frequency 6 format from a prior study (Storkel, Voelmle, et al., 2017) and taught a different set of words using an alternative format, either Dose 4 × Dose Frequency 9 or Dose 9 × Dose Frequency 4, determined through random assignment. Word learning was tracked for each treatment via a definition task prior to, during, and after treatment.

Results

Results showed that children with DLD learned a significant number of words during treatment regardless of the dose and dose frequency format but that significant forgetting of newly learned words occurred in all formats once treatment was withdrawn. Individual differences in word learning were related to Clinical Evaluation of Language Fundamentals Core Language and Understanding Spoken Paragraphs scores.

Conclusion

When administered at an adequate intensity, variation in the dose and dose frequency of interactive book reading does not appear to influence word learning by children with DLD. Although interactive book reading continues to show promise as an effective word learning intervention for children with DLD, further development is needed to enhance the effectiveness of this treatment approach.

Supplemental Material

https://doi.org/10.23641/asha.9745181

A real-time mechanism underlying lexical deficits in developmental language disorder: Between-word inhibition

Eight to 11% of children have a clinical disorder in oral language (Developmental Language Disorder, DLD). Language deficits in DLD can affect all levels of language and persist through adulthood. Word-level processing may be critical as words link phonology, orthography, syntax and semantics. Thus, a lexical deficit could cascade throughout language. Cognitively, word recognition is a competition process: as the input (e.g., lizard) unfolds, multiple candidates (liver, wizard) compete for recognition. Children with DLD do not fully resolve this competition, but it is unclear what cognitive mechanisms underlie this. We examined lexical inhibition-the ability of more active words to suppress competitors-in 79 adolescents with and without DLD. Participants heard words (e.g. net) in which the onset was manipulated to briefly favor a competitor (neck). This was predicted to inhibit the target, slowing recognition. Word recognition was measured using a task in which participants heard the stimulus, and clicked on a picture of the item from an array of competitors, while eye-movements were monitored as a measure of how strongly the participant was committed to that interpretation over time. TD listeners showed evidence of inhibition with greater interference for stimuli that briefly activated a competitor word. DLD listeners did not. This suggests deficits in DLD may stem from a failure to engage lexical inhibition. This in turn could have ripple effects throughout the language system. This supports theoretical approaches to DLD that emphasize lexical-level deficits, and deficits in real-time processing.

Neurophysiological Correlates of Fast Mapping of Novel Words in the Adult Brain

Word acquisition could be mediated by the neurocognitive mechanism known as fast mapping (FM). It refers to a process of incidental exclusion-based learning and is believed to be a critical mechanism for the rapid build-up of lexicon, although its neural mechanisms are still poorly understood. To investigate the neural bases of this key learning skill, we used event-related potentials (ERPs) and employed an audio-visual paradigm that included a counterbalanced set of familiar and novel spoken word forms presented, in a single exposure, in conjunction with novel and familiar images. To define learning-related brain dynamics, passive auditory ERPs, known to index long-term memory trace activation, were recorded before and after the FM task. Following the single FM learning exposure, we found a significant enhancement in neural activation elicited by the newly trained word form, which was expressed at ~200-400 ms after the word onset. No similar amplitude increase was found either for the native familiar word used as a control stimulus in the same learning paradigm or for similar control stimuli which were not subject to training. Topographic analysis suggested a left-lateral shift of the ERP scalp distribution for the novel FM word form, underpinned by fronto-temporal cortical sources, which may indicate the involvement of pre-existing neurolinguistic networks for mastering new word forms with native phonology. Overall, the near-instant changes in neural activity after a single-shot novel word training indicate that FM could promote rapid integration of newly learned items into the brain's neural lexicon, even in adulthood.

Association of Midlife Hearing Impairment With Late-Life Temporal Lobe Volume Loss

IMPORTANCE

Hearing impairment (HI) in midlife (45-65 years of age) may be associated with longitudinal neurodegeneration of temporal lobe structures, a biomarker of early Alzheimer disease.

OBJECTIVE

To evaluate the association of midlife HI with brain volume trajectories in later life (≥65 years of age).

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study used data from the Baltimore Longitudinal Study of Aging to evaluate hearing from November 5, 1990, to October 3, 1994, and late-life volume change from July 10, 2008, to January 29, 2015, using magnetic resonance imaging (MRI) (mean follow-up time, 19.3 years). Data analysis was performed from September 22, 2017, to August 27, 2018. A total of 194 community-dwelling older adults who had midlife measures of peripheral hearing at a mean age of 54.5 years and late-life volume change of up to 6 years between the first and most recent MRI assessment were studied. Excluded were those with baseline cognitive impairment, stroke, head injuries, Parkinson disease, and bipolar disorder.

EXPOSURES

Hearing as measured with pure tone audiometry in each ear from November 5, 1990, to October 3, 1994, and late-life temporal lobe volume change measured by MRI.

MAIN OUTCOMES AND MEASURES

Linear mixed-effects models with random intercepts were used to examine the association of midlife hearing (pure tone average of 0.5-4 kHz tones in the better ear and each ear separately) with longitudinal late-life MRI-based measures of temporal lobe structures (hippocampus, entorhinal cortex, parahippocampal gyrus, and superior, middle, and inferior temporal gyri) in the left and right hemispheres, in addition to global and lobar regions, adjusting for baseline demographic characteristics (age, sex, subsequent cognitive impairment status, and educational level) and intracranial volume.

RESULTS

A total of 194 patients (mean [SD] age at hearing assessment, 54.5 [10.0] years; 106 [54.6%] female; 169 [87.1%] white) participated in the study. After Bonferroni correction, poorer midlife hearing in the better ear was associated with steeper late-life volumetric declines in the right temporal gray matter (β = -0.113; 95% CI, -0.182 to -0.044), right hippocampus (β = -0.008; 95% CI, -0.012 to -0.004), and left entorhinal cortex (β = -0.009; 95% CI, -0.015 to -0.003). Poorer midlife hearing in the right ear was associated with steeper late-life volumetric declines in the right temporal gray matter (β = -0.136; 95% CI, -0.197 to -0.075), right hippocampus (β = -0.008; 95% CI, -0.012 to -0.004), and left entorhinal cortex (β = -0.009; 95% CI, -0.015 to -0.003), whereas there were no associations between poorer midlife hearing in the left ear with late-life volume loss.

CONCLUSIONS AND RELEVANCE

The findings suggest that midlife HI is a risk factor for temporal lobe volume loss. Poorer midlife hearing, particularly in the right ear, was associated with declines in hippocampus and entorhinal cortex.

Adult Fast-Mapping Memory Research Is Based on a Misinterpretation of Developmental-Word-Learning Data

Fast mapping is often used to refer to children’s remarkable ability to learn the meanings of new words with minimal exposure and in ambiguous contexts. It is one thing to claim that children are capable of learning words this way; it is another to claim that this ability relies on a specific fast-mapping neurocognitive mechanism that is critical for early word learning. Yet that claim has recently been made in adult memory research and used as a theoretical justification for research into an adult fast-mapping mechanism. In this review, we explain why the existence of such a mechanism in children is not supported by developmental research and explore the implications for adult fast-mapping data and research.

Language Training Leads to Global Cognitive Improvement in Older Adults: A Preliminary Study

Purpose We report a preliminary study that prospectively tests the potential cognitive enhancing effect of foreign language (FL) learning in older adults with no clear signs of cognitive decline beyond what is age typical. Because language learning engages a large brain network that overlaps with the network of cognitive aging, we hypothesized that learning a new language later in life would be beneficial. Method Older adults were randomly assigned to 3 training groups: FL, games, and music appreciation. All were trained predominately by a computer-based program for 6 months, and their cognitive abilities were tested before, immediately after, and 3 months after training. Results FL and games, but not music appreciation, improved overall cognitive abilities that were maintained at 3 months after training. Conclusion This is the 1st randomized control study providing preliminary support for the cognitive benefits of FL learning.

Little evidence for Fast Mapping (FM) in adults: A review and discussion

Conventional memory theory proposes that the hippocampus is initially responsible for encoding new information, before this responsibility is gradually transferred to the neocortex. Therefore, a report in 2011 by Sharon et al. of hippocampal-independent learning in humans was notable. These authors reported normal learning of new object-name associations under a Fast Mapping (FM) procedure in adults with hippocampal damage, who were amnesic according to more conventional explicit memorisation procedures. FM is an incidental learning paradigm, inspired by vocabulary acquisition in children, which is hypothesised to allow rapid, cortical-based memory formation. In the years since the original report, there has been, understandably, a growing interest in adult FM, not only because of its theoretical importance, but also because of its potential to help rehabilitate individuals with memory problems. We review the FM literature in individuals with amnesia and in healthy adults, using both explicit and implicit memory measures. Contrary to other recent reviews, we conclude that the evidence for FM in adults is weak, and restraint is needed before assuming the phenomenon exists.

Neural correlates of word learning in children

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We measured brain activity patterns for recognizing newly trained words in children.

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Retrieval related activation in the hippocampus decreased a week after training.

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Lexical integration effect was not observed even after a delay of 1 week.

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Younger group used right hemisphere more whereas teens used left hemisphere more.

Memory representations of words are thought to undergo changes with consolidation: Episodic memories of novel words are transformed into lexical representations that interact with other words in the mental dictionary. Behavioral studies have shown that this lexical integration process is enhanced when there is more time for consolidation. Neuroimaging studies have further revealed that novel word representations are initially represented in a hippocampally-centered system, whereas left posterior middle temporal cortex activation increases with lexicalization. In this study, we measured behavioral and brain responses to newly-learned words in children. Two groups of Dutch children, aged between 8–10 and 14–16 years, were trained on 30 novel Japanese words depicting novel concepts. Children were tested on word-forms, word-meanings, and the novel words’ influence on existing word processing immediately after training, and again after a week. In line with the adult findings, hippocampal involvement decreased with time. Lexical integration, however, was not observed immediately or after a week, neither behaviorally nor neurally. It appears that time alone is not always sufficient for lexical integration to occur. We suggest that other factors (e.g., the novelty of the concepts and familiarity with the language the words are derived from) might also influence the integration process.

Reasons to doubt the generalizability, reliability, and diagnosticity of fast mapping (FM) for rapid lexical integration

The possibility of fast mapping (FM) promoting rapid lexical integration challenges complementary systems accounts of word learning. Here, we first question the diagnosticity of orthographic lexical competition prior to sleep as an indicator of lexical integration, given emerging evidence that the same pre-sleep effect can be found with explicit learning paradigms. Second, we describe a study that showed no evidence of accelerated lexical integration for spoken-word learning. This study also found no FM advantage when written materials were used . Taken together, the evidence does not convincingly demonstrate that FM can accelerate lexical integration in healthy adults.

Learning to live with interfering neighbours: the influence of time of learning and level of encoding on word learning

New vocabulary is consolidated offline, particularly during sleep; however, the parameters that influence consolidation remain unclear. Two experiments investigated effects of exposure level and delay between learning and sleep on adults' consolidation of novel competitors (e.g. BANARA) to existing words (e.g. BANANA). Participants made speeded semantic decisions (i.e. a forced choice: natural versus man-made) to the existing words, with the expectation that novel word learning would inhibit responses due to lexical competition. This competition was observed, particularly when assessed after sleep, for both standard and high exposure levels (10 and 20 exposures per word; Experiment 1). Using a lower exposure level (five exposures; Experiment 2), no post-sleep enhancement of competition was observed, despite evidence of consolidation when explicit knowledge of novel word memory was tested. Thus, when encoding is relatively weak, consolidation-related lexical integration is particularly compromised. There was no evidence that going to bed soon after learning is advantageous for overnight consolidation; however, there was some preliminary suggestion that longer gaps between learning and bed-onset were associated with better explicit memory of novel words one week later, but only at higher levels of exposure. These findings suggest that while lexical integration can occur overnight, weaker lexical traces may not be able to access overnight integration processes in the sleeping brain. Furthermore, the finding that longer-term explicit memory of stronger (but not weaker) traces benefit from periods of wake following learning deserves examination in future research.

Knowledge is power: Prior knowledge aids memory for both congruent and incongruent events, but in different ways

Events that conform to our expectations, that is, are congruent with our world knowledge or schemas, are better remembered than unrelated events. Yet events that conflict with schemas can also be remembered better. We examined this apparent paradox in 4 experiments, in which schemas were established by training ordinal relationships between randomly paired objects, whereas event memory was tested for the number of objects on each trial. Better memory was found for both congruent and incongruent trials, relative to unrelated trials, producing memory performance that was a "U-shaped" function of congruency. The congruency advantage but not incongruency advantage was mediated by postencoding processes, whereas the incongruency advantage, but not congruency advantage, emerged even if the information probed by the memory test was irrelevant to the schema. Schemas therefore augment event memory in multiple ways, depending on the match between novel and existing information. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Depth of Encoding Through Observed Gestures in Foreign Language Word Learning

Word learning is basic to foreign language acquisition, however time consuming and not always successful. Empirical studies have shown that traditional (visual) word learning can be enhanced by gestures. The gesture benefit has been attributed to depth of encoding. Gestures can lead to depth of encoding because they trigger semantic processing and sensorimotor enrichment of the novel word. However, the neural underpinning of depth of encoding is still unclear. Here, we combined an fMRI and a behavioral study to investigate word encoding online. In the scanner, participants encoded 30 novel words of an artificial language created for experimental purposes and their translation into the subjects' native language. Participants encoded the words three times: visually, audiovisually, and by additionally observing semantically related gestures performed by an actress. Hemodynamic activity during word encoding revealed the recruitment of cortical areas involved in stimulus processing. In this study, depth of encoding can be spelt out in terms of sensorimotor brain networks that grow larger the more sensory modalities are linked to the novel word. Word retention outside the scanner documented a positive effect of gestures in a free recall test in the short term.

Offline consolidation supersedes prior knowledge benefits in children's (but not adults') word learning

Prior linguistic knowledge is proposed to support the acquisition and consolidation of new words. Adults typically have larger vocabularies to support word learning than children, but the developing brain shows enhanced neural processes that are associated with offline memory consolidation. This study investigated contributions of prior knowledge to initial word acquisition and consolidation at different points in development, by teaching children and adults novel words (e.g., ballow) that varied in the number of English word-form "neighbours" (e.g., wallow, bellow). Memory for the novel word-forms was tested immediately after training, the next day and 1 week later, to assess the time-course of prior knowledge contributions. Children aged 7-9 years (Experiments 1, 3) and adults (Experiment 2) recalled words with neighbours better than words without neighbours when tested immediately after training. However, a period of offline consolidation improved overall recall and reduced the influence of word-form neighbours on longer term memory. These offline consolidation benefits were larger in children than adults, supporting theories that children have a greater propensity for consolidating phonologically distinctive language information. Local knowledge of just a single word-form neighbour was enough to enhance learning, and this led to the individual differences in word recall that were related to adults' global vocabulary ability. The results support the proposal that the relative contributions of different learning mechanisms change across the lifespan, and highlight the importance of testing theoretical models of word learning in the context of development.

Contextual priming of word meanings is stabilized over sleep

Evidence is growing for the involvement of consolidation processes in the learning and retention of language, largely based on instances of new linguistic components (e.g., new words). Here, we assessed whether consolidation effects extend to the semantic processing of highly familiar words. The experiments were based on the word-meaning priming paradigm in which a homophone is encountered in a context that biases interpretation towards the subordinate meaning. The homophone is subsequently used in a word-association test to determine whether the priming encounter facilitates the retrieval of the primed meaning. In Experiment 1 (N = 74), we tested the resilience of priming over periods of 2 and 12 h that were spent awake or asleep, and found that sleep periods were associated with stronger subsequent priming effects. In Experiment 2 (N = 55) we tested whether the sleep benefit could be explained in terms of a lack of retroactive interference by testing participants 24 h after priming. Participants who had the priming encounter in the evening showed stronger priming effects after 24 h than participants primed in the morning, suggesting that sleep makes priming resistant to interference during the following day awake. The results suggest that consolidation effects can be found even for highly familiar linguistic materials. We interpret these findings in terms of a contextual binding account in which all language perception provides a learning opportunity, with sleep and consolidation contributing to the updating of our expectations, ready for the next day.

Formation of neocortical memory circuits for unattended written word forms: neuromagnetic evidence

To master linguistic communication, humans must acquire large vocabularies quickly and effortlessly. Efficient word learning might be facilitated by the ability to rapidly acquire novel word forms even outside the focus of attention, occurring within minutes of repetitive exposure and suggesting fast and automatic lexicon acquisition. However, this phenomenon has been studied in the auditory modality only, and it is unknown whether similar mechanisms also exist in the visual domain. We tested this by presenting participants with novel written word forms while the focus of their attention was on a non-linguistic dual colour-detection task. Matched familiar word forms served as a control. Using magnetoencephalography (MEG), we scrutinised changes in neuromagnetic responses to familiar and to novel word forms over approximately 15 minutes of exposure. We found, for the first time, a visual analogue of automatic rapid build-up of neural memory circuits for unattended novel lexical items, seen as a rapid enhancement of early (~100 ms post-onset) activation in the left anterior-superior temporal lobe. Our results suggest that the brain quickly forms cortical representations for new written forms, and indicate that the automatic neural mechanisms subserving rapid online acquisition of novel linguistic information might be shared by both auditory and visual modalities.

Listeners and readers generalize their experience with word meanings across modalities

Research has shown that adults' lexical-semantic representations are surprisingly malleable. For instance, the interpretation of ambiguous words (e.g., bark) is influenced by experience such that recently encountered meanings become more readily available (Rodd et al., 2016, 2013). However, the mechanism underlying this word-meaning priming effect remains unclear, and competing accounts make different predictions about the extent to which information about word meanings that is gained within one modality (e.g., speech) is transferred to the other modality (e.g., reading) to aid comprehension. In two Web-based experiments, ambiguous target words were primed with either written or spoken sentences that biased their interpretation toward a subordinate meaning, or were unprimed. About 20 min after the prime exposure, interpretation of these target words was tested by presenting them in either written or spoken form, using word association (Experiment 1, N = 78) and speeded semantic relatedness decisions (Experiment 2, N = 181). Both experiments replicated the auditory unimodal priming effect shown previously (Rodd et al., 2016, 2013) and revealed significant cross-modal priming: primed meanings were retrieved more frequently and swiftly across all primed conditions compared with the unprimed baseline. Furthermore, there were no reliable differences in priming levels between unimodal and cross-modal prime-test conditions. These results indicate that recent experience with ambiguous word meanings can bias the reader's or listener's later interpretation of these words in a modality-general way. We identify possible loci of this effect within the context of models of long-term priming and ambiguity resolution. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Small Sets of Novel Words Are Fully Retained After 1-Week in Typically Developing Children and Down Syndrome: A Fast Mapping Study

OBJECTIVES

Down syndrome (DS) is a population with known hippocampal impairment, with studies showing that individuals with DS display difficulties in spatial navigation and remembering arbitrary bindings. Recent research has also demonstrated the importance of the hippocampus for novel word-learning. Based on these data, we aimed to determine whether individuals with DS show deficits in learning new labels and if they may benefit from encoding conditions thought to be less reliant on hippocampal function (i.e., through fast mapping).

METHODS

In the current study, we examined immediate, 5-min, and 1-week delayed word-learning across two learning conditions (e.g., explicit encoding vs. fast mapping). These conditions were examined across groups (twenty-six 3- to 5-year-old typically developing children and twenty-six 11- to 28-year-old individuals with DS with comparable verbal and nonverbal scores on the Kaufman Brief Intelligence Test - second edition) and in reference to sleep quality.

RESULTS

Both individuals with and without DS showed retention after a 1-week delay, and the current study found no benefit of the fast mapping condition in either group contrary to our expectations. Eye tracking data showed that preferential eye movements to target words were not present immediately but emerged after 1-week in both groups. Furthermore, sleep measures collected via actigraphy did not relate to retention in either group.

CONCLUSIONS

This study presents novel data on long-term knowledge retention in reference to sleep patterns in DS and adds to a body of knowledge helping us to understand the processes of word-learning in typical and atypically developing populations. (JINS, 2018, 24, 955-965).

When two are better than one: Bilateral mesial temporal lobe contributions associated with better vocabulary skills in children and adolescents

This study considered the involvement of the mesial temporal lobe (MTL) in language and verbal memory functions in healthy children and adolescents. We investigated 30 healthy, right-handed children and adolescents, aged 7-16, with a fMRI language paradigm and a comprehensive cognitive test battery. We found significant MTL activations during language fMRI in all participants; 63% of them had left lateralized MTL activations, 20% exhibited right MTL lateralization, and 17% showed bilateral MTL involvement during the fMRI language paradigm. Group analyses demonstrated a strong negative correlation between the lateralization of MTL activations and language functions. Specifically, children with less lateralized MTL activation showed significantly better vocabulary skills. These findings suggest that the mesial temporal lobes of both hemispheres play an important role in language functioning, even in right-handers. Our results furthermore show that bilateral mesial temporal lobe involvement is advantageous for vocabulary skills in healthy, right-handed children and adolescents.

Learning new meanings for known words: Perturbation of original meanings and retention of new meanings

Learning a new, unrelated meaning for a known word faces competition from the word's original meaning. Moreover, the connection of the word with its original meaning also shows a subtle form of interference, a perturbation, when tested immediately after learning. However, the long-term effects of both types of interference are unclear. The present study paired both high and low frequency words with new unrelated meanings, testing the fate of new and original meanings on three different days over one week as a function of word familiarity. The results were that learners maintained memory for new meanings of high frequency words better than the new meanings of low frequency words over one week. Following learning, meaning decisions on high frequency words that required the original meaning of the trained word were delayed relative to decisions on control words - but only when testing was immediate and the stimulus-onset asynchrony (SOA) between the trained word and its original meaning probe was 200 ms. When the SOA was 500 ms or when the test was delayed by one day or one week, no effect occurred. The findings indicate that in the learning of new meanings for known words, word familiarity benefits long-term retention of new meanings. The facilitation effect occurs along with a perturbation effect, in which the original meaning of a familiar word is made momentarily less accessible immediately after learning.