Linking neurogenetics and individual differences in language learning: the dopamine hypothesis

Associations between Neonicotinoid, Pyrethroid, and Organophosphate Insecticide Metabolites and Neurobehavioral Performance in Ecuadorian Adolescents

Background

Organophosphate and pyrethroid insecticides can affect children's neurodevelopment and increase inflammation. Limited evidence exists among adolescents and on whether inflammation may mediate pesticide-neurobehavior associations. We examined the associations between insecticide metabolite concentrations and neurobehavior among adolescents in Ecuadorian agricultural communities.

Methods

We included 520 participants aged 11-17 years. We measured urinary insecticide metabolites (mass spectrometry) and neurobehavior (NEPSY-II). Associations were adjusted for socio-demographic and anthropometric characteristics. The associations of insecticide mixtures with neurobehavior were evaluated using PLS regression, and mediation by inflammatory biomarkers (TNF-α, IL-6, CRP, SAA, sICAM-1, sVCAM-1 and sCD-14) was conducted.

Results

Among organophosphates, para-nitrophenol (PNP) and 3,5,6-Trichloro-2-pyridinol (TCPy) were inversely associated with Social Perception (score difference per 50% increase [β 50% ] = -0.26 [95%CI: - 1.07, -0.20] and -0.10 [-0.22, 0.01], respectively). PNP and TCPy also had significant inverse associations with Attention/Inhibitory Control at concentrations >60 th percentile (β 50% = -0.26 [95%CI: -0.51, -0.01] and β 50% = -0.22 [95%CI: -0.43, -0.00], respectively). The pyrethroid, 3-phenoxybenzoic acid (3-PBA), was inversely associated with Language (β 50% = -0.13 [95%CI: -0.19, -0.01]) and had a negative quadratic association with Attention/Inhibitory Control. The neonicotinoid 5-Hydroxy imidacloprid (OHIM) was positively associated with Memory/Learning (β 50% = 0.20 [95%CI: 0.04, 0.37]). Mixtures of all insecticides were significantly negatively related to all domains, except for Memory/Learning, which was positively associated. No mediation by inflammatory markers on these associations was observed.

Conclusions

Concurrent organophosphate, pyrethroid, and the mixtures of all metabolites were associated with lower performance in all domains except for Memory/Learning. Neonicotinoids were positively associated with Memory/Learning and Social Perception scores.

Vigilant attention mediates the association between resting EEG alpha oscillations and word learning ability

Individuals exhibit considerable variability in their capacity to learn and retain new information, including novel vocabulary. Prior research has established the importance of vigilance and electroencephalogram (EEG) alpha rhythm in the learning process. However, the interplay between vigilant attention, EEG alpha oscillations, and an individual's word learning ability (WLA) remains elusive. To address this knowledge gap, here we conducted two experiments with a total of 140 young and middle-aged adults who underwent resting EEG recordings prior to completing a paired-associate word learning task and a psychomotor vigilance test (PVT). The results of both experiments consistently revealed significant positive correlations between WLA and resting EEG alpha oscillations in the occipital and frontal regions. Furthermore, the association between resting EEG alpha oscillations and WLA was mediated by vigilant attention, as measured by the PVT. These findings provide compelling evidence supporting the crucial role of vigilant attention in linking EEG alpha oscillations to an individual's learning ability.

Age effects in second language acquisition: Expanding the emergentist account

In 2005, Science magazine designated the problem of accounting for difficulties in L2 (second language) learning as one of the 125 outstanding challenges facing scientific research. A maturationally-based sensitive period has long been the favorite explanation for why ultimate foreign language attainment declines with age-of-acquisition. However, no genetic or neurobiological mechanisms for limiting language learning have yet been identified. At the same time, we know that cognitive, social, and motivational factors change in complex ways across the human lifespan. Emergentist theory provides a framework for relating these changes to variation in the success of L2 learning. The great variability in patterns of learning, attainment, and loss across ages, social groups, and linguistic levels provides the core motivation for the emergentist approach. Our synthesis incorporates three groups of factors which change systematically with age: environmental supports, cognitive abilities, and motivation for language learning. This extended emergentist account explains why and when second language succeeds for some children and adults and fails for others.

Getting language right: Relating individual differences in right hemisphere contributions to language learning and relearning

Language, or the diverse set of dynamic processes through which symbolic, perceptual codes are linked to meaning representations in memory, has long been assumed to be lateralized to the left hemisphere (LH). However, after over 150 years of investigation, we still lack a unifying account of when, and for whom, a particular linguistic process relies upon LH or right hemisphere (RH) computations, or both. With a focus on individual differences, this article integrates existing theories of hemispheric contributions to language and cognition into a novel proposed framework for understanding how, when, and for whom the RH contributes to linguistic processes. We use evidence from first and second language learning and language relearning following focal brain damage to highlight the critical contributions of the RH.

Non-game like training benefits spoken foreign-language processing in children with dyslexia

Children with dyslexia often face difficulties in learning foreign languages, which is reflected as weaker neural activation. However, digital language-learning applications could support learning-induced plastic changes in the brain. Here we aimed to investigate whether plastic changes occur in children with dyslexia more readily after targeted training with a digital language-learning game or similar training without game-like elements. We used auditory event-related potentials (ERPs), specifically, the mismatch negativity (MMN), to study learning-induced changes in the brain responses. Participants were 24 school-aged Finnish-speaking children with dyslexia and 24 age-matched typically reading control children. They trained English speech sounds and words with "Say it again, kid!" (SIAK) language-learning game for 5 weeks between ERP measurements. During the game, the players explored game boards and produced English words aloud to score stars as feedback from an automatic speech recognizer. To compare the effectiveness of the training type (game vs. non-game), we embedded in the game some non-game levels stripped of all game-like elements. In the dyslexia group, the non-game training increased the MMN amplitude more than the game training, whereas in the control group the game training increased the MMN response more than the non-game training. In the dyslexia group, the MMN increase with the non-game training correlated with phonological awareness: the children with poorer phonological awareness showed a larger increase in the MMN response. Improved neural processing of foreign speech sounds as indicated by the MMN increase suggests that targeted training with a simple application could alleviate some spoken foreign-language learning difficulties that are related to phonological processing in children with dyslexia.

The Neurodegenerative Elderly Syndrome (NES) hypothesis: Alzheimer and Parkinson are two faces of the same disease

Increasing evidence suggests that Alzheimer's disease (AD) and Parkinson's disease (PD) share monoamine and alpha-synuclein (αSyn) dysfunctions, often beginning years before clinical manifestations onset. The triggers for these impairments and the causes leading these early neurodegenerative processes to become AD or PD remain unclear. We address these issues by proposing a radically new perspective to frame AD and PD: they are different manifestations of one only disease we call "Neurodegenerative Elderly Syndrome (NES)". NES goes through three phases. The seeding stage, which starts years before clinical signs, and where the part of the brain-body affected by the initial αSyn and monoamine dysfunctions, influences the future possible progression of NES towards PD or AD. The compensatory stage, where the clinical symptoms are still silent thanks to compensatory mechanisms keeping monoamine concentrations homeostasis. The bifurcation stage, where NES becomes AD or PD. We present recent literature supporting NES and discuss how this hypothesis could radically change the comprehension of AD and PD comorbidities and the design of novel system-level diagnostic and therapeutic actions.

Motor constellation theory: A model of infants' phonological development

Every normally developing human infant solves the difficult problem of mapping their native-language phonology, but the neural mechanisms underpinning this behavior remain poorly understood. Here, motor constellation theory, an integrative neurophonological model, is presented, with the goal of explicating this issue. It is assumed that infants' motor-auditory phonological mapping takes place through infants' orosensory "reaching" for phonological elements observed in the language-specific ambient phonology, via reference to kinesthetic feedback from motor systems (e.g., articulators), and auditory feedback from resulting speech and speech-like sounds. Attempts are regulated by basal ganglion-cerebellar speech neural circuitry, and successful attempts at reproduction are enforced through dopaminergic signaling. Early in life, the pace of anatomical development constrains mapping such that complete language-specific phonological mapping is prohibited by infants' undeveloped supralaryngeal vocal tract and undescended larynx; constraints gradually dissolve with age, enabling adult phonology. Where appropriate, reference is made to findings from animal and clinical models. Some implications for future modeling and simulation efforts, as well as clinical settings, are also discussed.

Contributions of common genetic variants to specific languages and to when a language is learned

Research over the past two decades has identified a group of common genetic variants explaining a portion of variance in native language ability. The present study investigates whether the same group of genetic variants are associated with different languages and languages learned at different times in life. We recruited 940 young adults who spoke from childhood Chinese and English as their first (native) (L1) and second (L2) language, respectively, who were learners of a new, third (L3) language. For the variants examined, we found a general decrease of contribution of genes to language functions from native to foreign (L2 and L3) languages, with variance in foreign languages explained largely by non-genetic factors such as musical training and motivation. Furthermore, genetic variants that were found to contribute to traits specific to Chinese and English respectively exerted the strongest effects on L1 and L2. These results seem to speak against the hypothesis of a language- and time-universal genetic core of linguistic functions. Instead, they provide preliminary evidence that genetic contribution to language may depend at least partly on the intricate language-specific features. Future research including a larger sample size, more languages and more genetic variants is required to further explore these hypotheses.

Diglossia Correlates With Prodromal Symptoms of Psychosis Among First-Generation Migrants

Background and Hypothesis

We have previously hypothesized that diglossia may be a risk factor for psychosis, drawing from observations on migration, ethnicity, social adversity, and language disturbances among others. However, empirical data on this association and the tools necessary for its measurement are limited.

Study Design

In a cross-sectional online sample of first-generation migrants residing in majority English-speaking countries, a response-based decision tree was introduced to classify the sociolinguistic profiles of 1497 participants as either with or without diglossia. Using multivariate logistic regression, the association of diglossia with psychosis risk screening outcomes in the Prodromal Questionnaire-16 was calculated, adjusting for demographic and linguistic confounders. Differences in the symptom categories endorsed between the 2 groups were also examined.

Study Results

Diglossia was identified in 18.4% of participants and was associated with an adjusted odds ratio of 2.58 for a positive risk screening outcome. Other significant factors included subjective social status, hearing difficulty, age, sex, country of residence, education level, and cannabis consumption. The effects of ethnicity, age at migration, fluency, relationship, and employment status were no more significant in the multivariate model. Finally, the largest differences in the proportion of positively responding participants between the two groups were found in symptoms relating to thought insertion and thought broadcasting.

Conclusions

In a sociolinguistic hierarchical framework, diglossia is correlated with prodromal symptoms of psychosis in first-generation migrants.

Vocal Learning and Behaviors in Birds and Human Bilinguals: Parallels, Divergences and Directions for Research

Comparisons between the communication systems of humans and animals are instrumental in contextualizing speech and language into an evolutionary and biological framework and for illuminating mechanisms of human communication. As a complement to previous work that compares developmental vocal learning and use among humans and songbirds, in this article we highlight phenomena associated with vocal learning subsequent to the development of primary vocalizations (i.e., the primary language (L1) in humans and the primary song (S1) in songbirds). By framing avian “second-song” (S2) learning and use within the human second-language (L2) context, we lay the groundwork for a scientifically-rich dialogue between disciplines. We begin by summarizing basic birdsong research, focusing on how songs are learned and on constraints on learning. We then consider commonalities in vocal learning across humans and birds, in particular the timing and neural mechanisms of learning, variability of input, and variability of outcomes. For S2 and L2 learning outcomes, we address the respective roles of age, entrenchment, and social interactions. We proceed to orient current and future birdsong inquiry around foundational features of human bilingualism: L1 effects on the L2, L1 attrition, and L1<–>L2 switching. Throughout, we highlight characteristics that are shared across species as well as the need for caution in interpreting birdsong research. Thus, from multiple instructive perspectives, our interdisciplinary dialogue sheds light on biological and experiential principles of L2 acquisition that are informed by birdsong research, and leverages well-studied characteristics of bilingualism in order to clarify, contextualize, and further explore S2 learning and use in songbirds.

Language and nonlanguage factors in foreign language learning: evidence for the learning condition hypothesis

The question of why native and foreign languages are learned with a large performance gap has prompted language researchers to hypothesize that they are subserved by fundamentally different mechanisms. However, this hypothesis may not have taken into account that these languages can be learned under different conditions (e.g., naturalistic vs. classroom settings). With a large sample of 636 third language (L3) learners who learned Chinese and English as their first (L1) and second (L2) languages, the present study examined the association of learning success across L1-L3. We argue that learning conditions may reveal how these languages are associated in terms of learning success. Because these languages were learned under a continuum of naturalistic to classroom conditions from L1 to L3, this sample afforded us a unique opportunity to evaluate the hypothesis that similar learning conditions between languages could be an important driving force determining language learning success. After controlling for nonlanguage factors such as musical background and motivational factors and using a convergence of analytics including the general linear models, the structural equation models, and machine learning, we found that the closer two languages were on the continuum of learning conditions, the stronger their association of learning success. Specifically, we found a significant association between L1 and L2 and between L2 and L3, but not between L1 and L3. Our results suggest that learning conditions may have important implications for the learning success of L1-L3.

Dissociation of tone merger and congenital amusia in Hong Kong Cantonese

While the issue of individual variation has been widely studied in second language learning or processing, it is less well understood how perceptual and musical aptitude differences can explain individual variation in native speech processing. In the current study, we make use of tone merger in Hong Kong Cantonese, an ongoing sound change that concerns the merging of tones in perception, production or both in a portion of native speakers, to examine the possible relationship between tone merger and musical and pitch abilities. Although a previous study has reported the occurrence of tone merger independently of musical training, it has not been investigated before whether tone-merging individuals, especially those merging tones in perception, would have inferior musical perception and fine-grained pitch sensitivities, given the close relationship of speech and music. To this end, we tested three groups of tone-merging individuals with various tone perception and production profiles on musical perception and pitch threshold tasks, in comparison to a group of Cantonese speakers with congenital amusia, and another group of controls without tone merger or amusia. Additionally, the amusics were compared with tone-merging individuals on the details of their tone discrimination and production profiles. The results showed a clear dissociation of tone merger and amusia, with the tone-merging individuals exhibiting intact musical and pitch abilities; on the other hand, the amusics demonstrated widespread difficulties in tone discrimination yet intact tone production, in contrast to the highly selective confusion of a specific tone pair in production or discrimination in tone-merging individuals. These findings provide the first evidence that tone merger and amusia are distinct from each other, and further suggest that the cause of tone merger may lie elsewhere rather than being driven by musical or pitch deficits. We also discussed issues arising from the current findings regarding the neural mechanisms of tone merger and amusia.

Thinking outside the box: The brain-bilingualism relationship in the light of early neurobiological variability

Bilingualism represents a distinctive way to investigate the interplay between brain and behaviour, and an elegant model to study the role of environmental factors in shaping this relationship. Past neuroimaging research has mainly focused on how bilingualism influences brain structure, and how eventually the brain accommodates a second language. In this paper, we discuss a more recent contribution to the field which views bilingualism as lens to understand brain-behaviour mappings from a different perspective. It has been shown, in contexts not related to bilingualism, that cognitive performance across several domains can be predicted by neuroanatomical variants determined prenatally and largely impervious to postnatal changes. Here, we discuss novel findings indicating that bilingualism modulates the predictive role of these variants on domain-specific cognition. The repercussions of these findings are potentially far-reaching on multiple levels, and highlight the need to shape more complex questions for progress in cognitive neuroscience approaches to bilingualism.

ASPM-lexical tone association in speakers of a tone language: Direct evidence for the genetic-biasing hypothesis of language evolution

How language has evolved into more than 7000 varieties today remains a question that puzzles linguists, anthropologists, and evolutionary scientists. The genetic-biasing hypothesis of language evolution postulates that genes and language features coevolve, such that a population that is genetically predisposed to perceiving a particular linguistic feature would tend to adopt that feature in their language. Statistical studies that correlated a large number of genetic variants and linguistic features not only generated this hypothesis but also specifically pinpointed a linkage between ASPM and lexical tone. However, there is currently no direct evidence for this association and, therefore, the hypothesis. In an experimental study, we provide evidence to link ASPM with lexical tone perception in a sample of over 400 speakers of a tone language. In addition to providing the first direct evidence for the genetic-biasing hypothesis, our results have implications for further studies of linguistic anthropology and language disorders.

Neuroemergentism: A Framework for Studying Cognition and the Brain

There has been virtual explosion of studies published in cognitive neuroscience primarily due to increased accessibility to neuroimaging methods, which has led to different approaches in interpretation. This review seeks to synthesize both developmental approaches and more recent views that consider neuroimaging. The ways in which Neuronal Recycling, Neural Reuse, and Language as Shaped by the Brain perspectives seek to clarify the brain bases of cognition will be addressed. Neuroconstructivism as an additional explanatory framework which seeks to bind brain and cognition to development will also be presented. Despite sharing similar goals, the four approaches to understanding how the brain is related to cognition have generally been considered separately. However, we propose that all four perspectives argue for a form of Emergentism in which combinations of smaller elements can lead to a greater whole. This discussion seeks to provide a synthesis of these approaches that leads to the emergence of a theory itself. We term this new synthesis Neurocomputational Emergentism (or Neuromergentism for short).

Cultural Genomics: Promises and Challenges

In this article, we attempt to integrate recent advances in our understanding of the relations between culture and genes into an emerging field—cultural genomics—and discuss its promises and theoretical and methodological challenges. We first provide a brief review of previous conceptualizations about the relations between culture and genes and then argue that recent advances in molecular evolution research has allowed us to reframe the discussion away from parallel genetic and cultural evolution to focus on the interactions between the two. After outlining the key issues involved in cultural genomics (unit of analysis, timescale, mechanisms, and direction of influence), we provide examples of research for the different levels of interactions between culture and genes. We then discuss ideological, theoretical, and methodological challenges in cultural genomics and propose tentative solutions.

Becoming a balanced, proficient bilingual: Predictions from age of acquisition & genetic background

Genetic variants related to dopamine functioning (e.g., the ANKK1/TaqIa polymorphism within the DRD2 gene and the Val158Met polymorphism within the COMT gene) have previously been shown to predict cognitive flexibility and learning (e.g., Colzato et al., 2010; Stelzel et al., 2010). Additionally, researchers have found that these genetic variants may also predict second language learning (Mamiya et al., 2016), although this relationship may change across the lifespan (Sugiura et al., 2011). The current study examined the role of the ANKK1/TaqIa and Val158Met polymorphisms along with age of second language acquisition (AoA) in order to predict levels of bilingual proficiency in Spanish-English bilinguals. Results indicated a three-way interaction such that the relationship between the genetic variants and bilingual proficiency depended on AoA. At earlier AoAs, having the genetic variant associated with higher levels of subcortical dopamine (A1+) predicted the highest levels of bilingual proficiency. At later AoAs, individuals with the genetic variant associated with cortical dopamine levels that are balanced between stability and flexibility (Val/Met) predicted the highest levels of bilingual proficiency. These results fit with theories about the development of language as a subcortical process early in life and as a cortical process later in life (Hernandez & Li, 2007), as well as the importance of both stability and flexibility in bilingual language development (Green & Abutalebi, 2013). Finally, this study raises questions about the direction of causality between bilingualism and cognitive control, which is central to the debate over the "bilingual advantage."

Plasticity, Variability and Age in Second Language Acquisition and Bilingualism

Much of what is known about the outcome of second language acquisition and bilingualism can be summarized in terms of inter-individual variability, plasticity and age. The present review looks at variability and plasticity with respect to their underlying sources, and at age as a modulating factor in variability and plasticity. In this context we consider critical period effects vs. bilingualism effects, early and late bilingualism, nativelike and non-nativelike L2 attainment, cognitive aging, individual differences in learning, and linguistic dominance in bilingualism. Non-uniformity is an inherent characteristic of both early and late bilingualism. This review shows how plasticity and age connect with biological and experiential sources of variability, and underscores the value of research that reveals and explains variability. In these ways the review suggests how plasticity, variability and age conspire to frame fundamental research issues in L2 acquisition and bilingualism, and provides points of reference for discussion of the present Frontiers in Psychology Research Topic.

Resting-state qEEG predicts rate of second language learning in adults

Understanding the neurobiological basis of individual differences in second language acquisition (SLA) is important for research on bilingualism, learning, and neural plasticity. The current study used quantitative electroencephalography (qEEG) to predict SLA in college-aged individuals. Baseline, eyes-closed resting-state qEEG was used to predict language learning rate during eight weeks of French exposure using an immersive, virtual scenario software. Individual qEEG indices predicted up to 60% of the variability in SLA, whereas behavioral indices of fluid intelligence, executive functioning, and working-memory capacity were not correlated with learning rate. Specifically, power in beta and low-gamma frequency ranges over right temporoparietal regions were strongly positively correlated with SLA. These results highlight the utility of resting-state EEG for studying the neurobiological basis of SLA in a relatively construct-free, paradigm-independent manner.

Examining Procedural Learning and Corticostriatal Pathways for Individual Differences in Language: Testing Endophenotypes of DRD2/ANKK1

The aim of the study was to explore whether genetic variation in the dopaminergic system is associated with procedural learning and the corticostriatal pathways in individuals with developmental language impairment (DLI). We viewed these two systems as endophenotypes and hypothesized that they would be more sensitive indicators of genetic effects than the language phenotype itself. Thus, we genotyped two SNPs in the DRD2/ANKK1 gene complex, and tested for their associations to the phenotype of DLI and the two endophenotypes. Results showed that individuals with DLI revealed poor procedural learning abilities and abnormal structures of the basal ganglia. Genetic variation in DRD2/ANKK1 was associated with procedural learning abilities and with microstructural differences of the caudate nucleus. The association of the language phenotype with these DRD2/ANKK1 polymorphisms was not significant, but the phenotype was significantly associated with the two endophenotypes. We suggest that procedural learning and the corticostriatal pathways could be used as effective endophenotypes to aid molecular genetic studies searching for genes predisposing to DLI.

The role of age and executive function in auditory category learning

Auditory categorization is a natural and adaptive process that allows for the organization of high-dimensional, continuous acoustic information into discrete representations. Studies in the visual domain have identified a rule-based learning system that learns and reasons via a hypothesis-testing process that requires working memory and executive attention. The rule-based learning system in vision shows a protracted development, reflecting the influence of maturing prefrontal function on visual categorization. The aim of the current study was twofold: (a) to examine the developmental trajectory of rule-based auditory category learning from childhood through adolescence and into early adulthood and (b) to examine the extent to which individual differences in rule-based category learning relate to individual differences in executive function. A sample of 60 participants with normal hearing-20 children (age range=7-12years), 21 adolescents (age range=13-19years), and 19 young adults (age range=20-23years)-learned to categorize novel dynamic "ripple" sounds using trial-by-trial feedback. The spectrotemporally modulated ripple sounds are considered the auditory equivalent of the well-studied "Gabor" patches in the visual domain. Results reveal that auditory categorization accuracy improved with age, with young adults outperforming children and adolescents. Computational modeling analyses indicated that the use of the task-optimal strategy (i.e., a conjunctive rule-based learning strategy) improved with age. Notably, individual differences in executive flexibility significantly predicted auditory category learning success. The current findings demonstrate a protracted development of rule-based auditory categorization. The results further suggest that executive flexibility coupled with perceptual processes play important roles in successful rule-based auditory category learning.

Beyond the bilingual advantage: The potential role of genes and environment on the development of cognitive control

In recent years there has been considerable debate about the presence or absence of a bilingual advantage in tasks that involve cognitive control. Our previous work has established evidence of differences in brain activity between monolinguals and bilinguals in both word learning and in the avoidance of interference during a picture selection task. Recent models of cognitive control have highlighted the importance of a set of neural structures that may show differential tuning due to exposure to two languages. There is also evidence that genetic factors play a role in the availability of dopamine in neural structures involved in cognitive control. Thus, it is important to investigate whether there are interactions effects generating variability in language acquisition when attributed to genetic (e.g., characteristics of dopamine turnover) and environmental (e.g., exposure to two languages) factors. Here preliminary results from genotyping of a sample of bilingual and monolingual individuals are reported. They reveal different distributions in allele frequencies of the DRD2/ANKK1 taq1A polymorphism. These results bring up the possibility that bilinguals may exhibit additional flexibility due to differences in genetic characteristics relative to monolinguals. Future studies should consider genotype as a possible contributing factor to the development of cognitive control across individuals with different language learning histories.

Poor phonetic perceivers are affected by cognitive load when resolving talker variability

Speech training paradigms aim to maximise learning outcomes by manipulating external factors such as talker variability. However, not all individuals may benefit from such manipulations because subject-external factors interact with subject-internal ones (e.g., aptitude) to determine speech perception and/or learning success. In a previous tone learning study, high-aptitude individuals benefitted from talker variability, whereas low-aptitude individuals were impaired. Because increases in cognitive load have been shown to hinder speech perception in mixed-talker conditions, it has been proposed that resolving talker variability requires cognitive resources. This proposal leads to the hypothesis that low-aptitude individuals do not use their cognitive resources as efficiently as those with high aptitude. Here, high- and low-aptitude subjects identified pitch contours spoken by multiple talkers under high and low cognitive load conditions established by a secondary task. While high-aptitude listeners outperformed low-aptitude listeners across load conditions, only low-aptitude listeners were impaired by increased cognitive load. The findings suggest that low-aptitude listeners either have fewer available cognitive resources or are poorer at allocating attention to the signal. Therefore, cognitive load is an important factor when considering individual differences in speech perception and training paradigms.

The Relationship Between Artificial and Second Language Learning

Artificial language learning (ALL) experiments have become an important tool in exploring principles of language and language learning. A persistent question in all of this work, however, is whether ALL engages the linguistic system and whether ALL studies are ecologically valid assessments of natural language ability. In the present study, we considered these questions by examining the relationship between performance in an ALL task and second language learning ability. Participants enrolled in a Spanish language class were evaluated using a number of different measures of Spanish ability and classroom performance, which was compared to IQ and a number of different measures of ALL performance. The results show that success in ALL experiments, particularly more complex artificial languages, correlates positively with indices of L2 learning even after controlling for IQ. These findings provide a key link between studies involving ALL and our understanding of second language learning in the classroom.

Procedural Learning and Individual Differences in Language

The aim of the current study was to examine different aspects of procedural memory in young adults who varied with regard to their language abilities. We selected a sample of procedural memory tasks, each of which represented a unique type of procedural learning, and has been linked, at least partially, to the functionality of the corticostriatal system. The findings showed that variance in language abilities is associated with performance on different domains of procedural memory, including the motor domain (as shown in the pursuit rotor task), the cognitive domain (as shown in the weather prediction task), and the linguistic domain (as shown in the nonword repetition priming task). These results implicate the corticostriatal system in individual differences in language.

Association between AVPR1A, DRD2, and ASPM and endophenotypes of communication disorders

OBJECTIVES

Speech sound disorder (SSD) is one of the most common communication disorders, with a prevalence rate of 16% at 3 years of age, and an estimated 3.8% of children still presenting speech difficulties at 6 years of age. Several studies have identified promising associations between communication disorders and genes in brain and neuronal pathways; however, there have been few studies focusing on SSD and its associated endophenotypes. On the basis of the hypothesis that neuronal genes may influence endophenotypes common to communication disorders, we focused on three genes related to brain and central nervous system functioning: the dopamine D2 receptor (DRD2) gene, the arginine-vasopressin receptor 1a (AVPR1A) gene, and the microcephaly-associated protein gene (ASPM).

METHODS

We examined the association of these genes with key endophenotypes of SSD - phonological memory measured through multisyllabic and nonword repetition, vocabulary measured using the Expressive One Word Picture Vocabulary Test and Peabody Picture Vocabulary Test, and reading decoding measured using the Woodcock Reading Mastery Tests Revised - as well as with the clinical phenotype of SSD. We genotyped tag single nucleotide polymorphisms in these genes and examined 498 individuals from 180 families.

RESULTS

These data show that several single nucleotide polymorphisms in all three genes were associated with phonological memory, vocabulary, and reading decoding, with P less than 0.05. Notably, associations in AVPR1A (rs11832266) were significant after multiple testing correction. Gene-level tests showed that DRD2 was associated with vocabulary, ASPM with vocabulary and reading decoding, and AVPR1A with all three endophenotypes.

CONCLUSION

Endophenotypes common to SSD, language impairment, and reading disability are all associated with these neuronal pathway genes.

Individual differences in behavioural plasticities

Interest in individual differences in animal behavioural plasticities has surged in recent years, but research in this area has been hampered by semantic confusion as different investigators use the same terms (e.g. plasticity, flexibility, responsiveness) to refer to different phenomena. The first goal of this review is to suggest a framework for categorizing the many different types of behavioural plasticities, describe examples of each, and indicate why using reversibility as a criterion for categorizing behavioural plasticities is problematic. This framework is then used to address a number of timely questions about individual differences in behavioural plasticities. One set of questions concerns the experimental designs that can be used to study individual differences in various types of behavioural plasticities. Although within-individual designs are the default option for empirical studies of many types of behavioural plasticities, in some situations (e.g. when experience at an early age affects the behaviour expressed at subsequent ages), 'replicate individual' designs can provide useful insights into individual differences in behavioural plasticities. To date, researchers using within-individual and replicate individual designs have documented individual differences in all of the major categories of behavioural plasticities described herein. Another important question is whether and how different types of behavioural plasticities are related to one another. Currently there is empirical evidence that many behavioural plasticities [e.g. contextual plasticity, learning rates, IIV (intra-individual variability), endogenous plasticities, ontogenetic plasticities) can themselves vary as a function of experiences earlier in life, that is, many types of behavioural plasticity are themselves developmentally plastic. These findings support the assumption that differences among individuals in prior experiences may contribute to individual differences in behavioural plasticities observed at a given age. Several authors have predicted correlations across individuals between different types of behavioural plasticities, i.e. that some individuals will be generally more plastic than others. However, empirical support for most of these predictions, including indirect evidence from studies of relationships between personality traits and plasticities, is currently sparse and equivocal. The final section of this review suggests how an appreciation of the similarities and differences between different types of behavioural plasticities may help theoreticians formulate testable models to explain the evolution of individual differences in behavioural plasticities and the evolutionary and ecological consequences of individual differences in behavioural plasticities.

Phenotypic features of children with neurodevelopmental diseases in relation to biogenic amines

Disruption of monoamines metabolism leads to diverse manifestations, including developmental, movement and respiratory dysfunctions. We aimed to correlate clinical phenotypes of 55 children with neurodevelopmental disorders with dopamine (HVA) and serotonin (5-HIIA) metabolites in CSF. Decreased level of at least one metabolite was documented in 49.1% patients. Both metabolites were significantly lower in progressive disorder and extrapyramidal syndrome (p<0.05). HVA was significantly lower in hypokinetic and regulatory disorders (p<0.05). In univariate analysis, only progressive course, extrapyramidal syndrome and dystonia were significantly associated with decreased 5-HIAA. In multivariate regression only progressive course remained significant (p=0.005). Progressive disease, extrapyramidal syndrome, dystonia, tremor and rigidity were positively associated with low HVA. In multivariate analysis only: progressive course and rigidity remained significant. Progressive/rigid phenotype carries a high risk of monoamines deficiency, strongly implying need for their analysis. Psychomotor delay with epilepsy and hypotonia is rarely linked to low monoamines level. Irrespective of final diagnosis, different clinical presentations may be associated with impaired monoamines turnover.

Genes and personality characteristics: Possible association of the genetic background with intelligence and decision making in 830 Caucasian Greek subjects

It is well known that intelligence consists of a variety of interactional and cognitive skills and abilities (e.g. tradecraft; critical and divergent thinking; perception of foreign information). Decision making is defined as the conscious choice between given options, relating to a problem. Both genetic background and environment comprise key elements for personality characteristics of the human being. The aim of this study is to determine the frequency distribution of rs324420, rs1800497, rs363050, rs6265, rs1328674 polymorphisms known to be involved in individual personality characteristics, in 830 Greek Subjects. The study is independent from direct clinical measurements (e.g. IQ measurements; physiological tests). The population of the volunteers is described, based on genotype, sex, with the respective gene frequencies, including the Minor Allele Frequency (MAF). A potential influence of the volunteer gender with the above characteristics (based on genotypes and alleles) is examined and finally, volunteers are classified as follows: A volunteer receives + 1, for each genotype/allele, which enhances his intelligence or his decision-making. In contrast, he receives - 1, for each genotype/allele, which relegates the individual characteristic. No statistically significant gender-characteristics correlation is observed. According to their genetic profile, a rate of 92.5%, of the volunteers may be characterized by prudence and temperance of thought, with only a small proportion of them (7.5%) may be classified as genetically spontaneous and adventurous. Regarding intelligence, the study population may lay around average and a little above it, at a rate of 96.3%, while the edges of the scale suggest only a 0.5% of the volunteers, who, although the "smartest", somehow seem to lack prudence. In conclusion, individuals with low cognitive ability may be more prudent than others and vice versa, while the "smartest" ones tend to be more risky, in decision-making. Therefore, intelligence and decision-making may, after all, be less linked to each other than expected.

Foreign language training as cognitive therapy for age-related cognitive decline: a hypothesis for future research

Over the next fifty years, the number of older adults is set to reach record levels. Protecting older adults from the age-related effects of cognitive decline is one of the greatest challenges of the next few decades as it places increasing pressure on families, health systems, and economies on a global scale. The disease-state of age-related cognitive decline-Alzheimer's disease and other dementias-hijacks our consciousness and intellectual autonomy. However, there is evidence that cognitively stimulating activities protect against the adverse effects of cognitive decline. Similarly, bilingualism is also considered to be a safeguard. We propose that foreign language learning programs aimed at older populations are an optimal solution for building cognitive reserve because language learning engages an extensive brain network that is known to overlap with the regions negatively affected by the aging process. It is recommended that future research should test this potentially fruitful hypothesis.

Linguistic grammar learning and DRD2-TAQ-IA polymorphism

As research into the neurobiology of language has focused primarily on the systems level, fewer studies have examined the link between molecular genetics and normal variations in language functions. Because the ability to learn a language varies in adults and our genetic codes also vary, research linking the two provides a unique window into the molecular neurobiology of language. We consider a candidate association between the dopamine receptor D2 gene (DRD2) and linguistic grammar learning. DRD2-TAQ-IA polymorphism (rs1800497) is associated with dopamine receptor D2 distribution and dopamine impact in the human striatum, such that A1 allele carriers show reduction in D2 receptor binding relative to carriers who are homozygous for the A2 allele. The individual differences in grammatical rule learning that are particularly prevalent in adulthood are also associated with striatal function and its role in domain-general procedural memory. Therefore, we reasoned that procedurally-based grammar learning could be associated with DRD2-TAQ-IA polymorphism. Here, English-speaking adults learned artificial concatenative and analogical grammars, which have been respectively associated with procedural and declarative memory. Language learning capabilities were tested while learners’ neural hemodynamic responses were simultaneously measured by fMRI. Behavioral learning and brain activation data were subsequently compared with the learners’ DRD2 (rs1800497) genotype. Learners who were homozygous for the A2 allele were better at concatenative (but not analogical) grammar learning and had higher striatal responses relative to those who have at least one A1 allele. These results provide preliminary evidence for the neurogenetic basis of normal variations in linguistic grammar learning and its link to domain-general functions.

Functional connectivity of substantia nigra and ventral tegmental area: maturation during adolescence and effects of ADHD

Dopaminergic (DArgic) pathways play crucial roles in brain function and their disruption is implicated in various neuropsychiatric diseases. Here, we demonstrate in 402 healthy children/adolescents (12 ± 3 years) and 704 healthy young adults (23 ± 5 years) that the functional connectivity of DA pathways matures significantly from childhood to adulthood and is different for healthy children and children with attention-deficit/hyperactivity disorder (ADHD; N = 203; 12 ± 3 years). This transition is characterized by age-related increases in the functional connectivity of the ventral tegmental area (VTA) with limbic regions and with the default mode network and by decreases in the connectivity of the substantia nigra (SN) with motor and medial temporal cortices. The changes from a predominant influence of SN in childhood/adolescence to a combined influence of SN and VTA in young adulthood might explain the increased vulnerability to psychiatric disorders, such as ADHD, early in life. We also show that VTA and SN connectivity networks were highly reproducible, which highlights their potential value as biomarkers for evaluating DArgic dysfunction in neuropsychiatric disorders.