Lapsen aivojen toiminnallinen kehitys kielenkehityksen näkökulmasta

Tämän syventävien opintojen kirjallisen työn aiheena on lapsen aivojen toiminnallinen kehitys, jota työssä tarkastellaan kielenkehityksen näkökulmasta. Työ on muodoltaan kirjallisuuskatsaus. Katsauksen tarkoituksena on luoda yleiskäsitys lapsen kielellisten tehtävien aikaisen aivotoiminnan ja aivojen rakenteen kehityksestä 2-12 ikävuoden välillä. Aihetta käsitellään laajasti eri kielen ulottuvuuksien, kuten lukemisen, puheen tuoton ja kielen ymmärtämisen, kautta. Katsaus keskittyy terveiden lasten normaalikehitykseen ja pyrkii ymmärtämään lapsen aivojen toiminnalle ominaisia piirteitä ja niiden kehitystä kohti aikuistyppistä aivotoimintaa. Kirjallisuuskatsauksen aineiston muodostavat PubMed-tietokannasta haetut lapsuuden aikaista aivotoimintaa ja kielellistä tiedonkäsittelyä käsittelevät artikkelit. Katsaukseen hyväksyttiin ainoastaan 2-12 -vuotiaita terveitä ja normaalisti kehittyviä lapsia käsitteleviä tutkimuksia. Lisäksi valittujen tutkimusten tuli käsitellä kielitaitojen ja aivojen toiminnan välistä yhteyttä. Lapsen aivojen toiminta kielellisen tiedonkäsittelyn aikana muistuttaa suurelta osin aikuistyppistä jo alle 5-vuotiaasta lähtien, mutta lasten ja aikuisten välillä on havaittavissa myös eroavaisuuksia. Lapsilla aktivoituvat kielenkäsittelyn aikana pitkälti samat aivoalueet kuin aikuisilla, mutta lapset hyödyntävät tunnettujen kielialueiden lisäksi aikuisia laajemmin myös epäspesifejä aivojen apualueita. Kehityksen ja taitojen karttumisen edetessä aivotoiminta kohdentuu tiukemmin tehtäväspesifisille aivoalueille, jolloin apualueiden rooli vähenee. Kohdentumisen aikataulu ja voimakkuus vaihtelevat kielen eri ulottuvuuksien ja yksilöiden välillä. Lapset myös hyödyntävät aikuisia laajemmin molempia aivopuoliskoja kielellisessä tiedonkäsittelyssään, vaikkakin lapsuuden aikaisessa lateralisaatioasteessa ja sen kehityksessä on merkittäviä eroja kielen eri ulottuvuuksien välillä

Deficient orthographic and phonological representations in children with dyslexia revealed by brain activation patterns

Background: The current study examined the neuro-cognitive network of visual word rhyming judgment in 14 children with dyslexia and 14 age-matched control children (8-to 14-year-olds) using functional magnetic resonance imaging (fMRI). Methods: In order to manipulate the difficulty of mapping orthography to phonology, we used conflicting and non-conflicting trials. The words in conflicting trials either had similar orthography but different phonology (e.g., pint-mint) or similar phonology but different orthography (e.g., jazz-has). The words in non-conflicting trials had similar orthography and phonology (e.g., gate-hate) or different orthography and phonology (e.g., presslist). Results: There were no differences in brain activation between the controls and children with dyslexia in the easier non-conflicting trials. However, the children with dyslexia showed less activation than the controls in left inferior frontal gyrus (BA 45/44/47/9), left inferior parietal lobule (BA 40), left inferior temporal gyrus/fusiform gyrus (BA 20/37) and left middle temporal gyrus (BA 21) for the more difficult conflicting trials. For the direct comparison of conflicting minus non-conflicting trials, controls showed greater activation than children with dyslexia in left inferior frontal gyrus (BA 9/45/46) and medial frontal gyrus (BA 8). Children with dyslexia did not show greater activation than controls for any comparison. Conclusions: Reduced activation in these regions suggests that children with dyslexia have deficient orthographic representations in ventral temporal cortex as well as deficits in mapping between orthographic and phonological representations in inferior parietal cortex. The greater activation for the controls in inferior frontal gyrus could reflect more effective top-down modulation of posterior representations

Early detection of markers for synaesthesia in childhood populations

We show that the neurological condition of synaesthesia-which causes fundamental differences in perception and cognition throughout a lifetime-is significantly represented within the childhood population, and that it manifests behavioural markers as young as age 6 years. Synaesthesia gives rise to a merging of cognitive and/or sensory functions (e.g. in grapheme-colour synaesthesia, reading letters triggers coloured visual photisms) and adult synaesthesia is characterized by a fixed pattern of paired associations for each synaesthete (e.g. if a is carmine red, it is always carmine red). We demonstrate that the onset of this systematicity can be detected in young grapheme-colour synaesthetes, but is an acquired trait with a protracted development. We show that grapheme-colour synaesthesia develops in a way that supersedes the cognitive growth of non-synaesthetic children (with both average and superior abilities) in a comparable paired association task. With methodology based on random sampling and behavioural tests of genuineness, we reveal the prevalence of grapheme-colour synaesthesia in children (over 170 000 grapheme-colour synaesthetes ages 0-17 in the UK, and over 930 000 in the US), the progression of the condition in longitudinal testing, and the developmental differences between synaesthetes and non-synaesthetes in matched tasks. We tested 615 children age 6-7 years from 21 primary schools in the UK. Each child was individually assessed with a behavioural test for grapheme-colour synaesthesia, which first detects differences between synaesthetes and non-synaesthetes, and then tracks the development of each group across 12 months (from ages 6/7 to 7/8 years). We show that the average UK primary school has 2-3 grapheme-colour synaesthetes at any time (and the average US primary school has five) and that synaesthetic associations (e.g. a = carmine red) develop from chaotic pairings into a system of fixed, consistent cogno-sensory responses over time. Our study represents the first assessment of synaesthesia in a randomly sampled childhood population demonstrating the real-time development of the condition. We discuss the complex profile of benefits and costs associated with synaesthesia, and our research calls for a dialogue between researchers, clinicians and educators to highlight the prevalence and characteristics of this unusual condition

Relaciones conceptuales: definición del constructo, bases neuroanatómicas y formas de evaluación/Conceptual relations: construct definition, neuroanatomical basis and ways of assessment

The links that connect concepts are called conceptual relations. Two of them have particular relevance in the organization of conceptual knowledge: taxonomic and thematic relations. Early research in the 80`s focused on analyzing the existence of a primacy of one kind of conceptual relation over the other in children and adults. Recent studies explore the neuroanatomical bases of these conceptual relations. The present work constitutes a revision of the most relevant studies about taxonomic and thematic conceptual relations, including developmental studies, research on neuroanatomical bases and available ways of assessment. The revised articles state that thematic and taxonomic conceptual relations involve dissociable cognitive processes that can be acquired and damaged independently and have independent neuroanatomical basis. Futures lines of research are also suggested.Resumen. Las relaciones conceptuales son los vínculos que conectan a los conceptos entre sí. Hay dos de ellas que tienen particular relevancia para la organización del conocimiento conceptual: las taxonómicas y las temáticas. Las investigaciones iniciales realizadas en la década del 80 se centraron en analizar si existía una primacía de un tipo de relaciones sobre el otro tanto en niños como en adultos. Los estudios más recientes están investigando sus bases neuroanatómicas. El presente trabajo constituye una revisión de los trabajos más relevantes sobre las relaciones conceptuales taxonómicas y temáticas, abarcando los estudios sobre distintas etapas del desarrollo, las bases neuroanatómicas y las formas de evaluación disponibles. Los artículos revisados afirman que las relaciones conceptuales taxonómicas y temáticas implican procesos cognitivos que pueden ser disociados, por lo tanto, se adquieren y dañan de manera independiente y tienen correlatos neuroanatómicos independientes. Se sugieren también posibles líneas de investigación futuras. 

Speech lateralization and motor control

A relationship between motor control and speech lateralization has long been postulated by researchers and clinicians with an interest in the functional organization of the human brain. Exactly how motor control might be related to speech representation, however, is rarely examined. This chapter examines current issues relating to the organization, development and measurement of motor control and speech representation. We further consider from neuropsychological, developmental, neurological and genetic perspectives that speech and fine motor control involve planning and sequencing processes, which are mediated by an integrated neural network localized to the left hemisphere. Specifically, we discuss studies from our laboratory using functional Transcranial Doppler ultrasonography to determine speech laterality, correlating this with hand preference and pegboard measures of motor laterality. Our findings show that handedness, as measured by a motor skill task, can be predictive of speech laterality, both in typically developing adults and children. We have also shown that individuals with developmental motor coordination impairments also show atypical speech lateralization, providing further evidence that neurological motor and speech systems are intrinsically connected. We consider these results in the context of a left lateralized speech-praxis center model, which could account for the relationship shown between sequenced-based motor and speech tasks

Language assessment in mesial temporal lobe epilepsy : correlations with structural and functional neuroimaging

Orientadores: Fernando Cendes, Marcio Luiz Figueredo BalthazarTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências MédicasResumo: A epilepsia de lobo temporal (ELT) é o tipo de epilepsia mais comum no adulto e comorbidades cognitivas podem acompanhá-la, como prejuízos de memória e linguagem. Nesta população é esperada uma maior incidência de pessoas com lateralização atípica para linguagem (LAL), 20% contra 5% da população saudável. Alguns fatores são apontados como preditores: dominância manual, sinistralidade familiar e insulto cerebral precoce e em hemisfério esquerdo. A linguagem nesses pacientes tem sido estudada há décadas, mas ultimamente a técnica de ressonância magnética funcional (fMRI) vem substituindo o teste de WADA e proporcionado uma série de novos métodos e paradigmas para estudar essa função in vivo, inclusive em indivíduos saudáveis. Portanto, o objetivo desse estudo foi delinear os subtipos de ELT, com atrofia esquerda (AHE), direita (AHD) e sem atrofia (negAH) hipocampal comparando-os com controles, quanto a aspectos de linguagem. Os resultados foram dispostos em dois artigos. O primeiro tratou da comparação de dois paradigmas de fMRI de linguagem baseados em decisão semântica. Neste artigo, 24 indivíduos saudáveis foram submetidos a duas versões de tarefa de linguagem: versão complexa e versão fácil. Ambas foram efetivas, porém a versão complexa produziu resultados mais robustos para a avaliação da linguagem. Logo, foi a versão eleita para conduzir o estudo com os pacientes ELT. O segundo resultado, foi exposto no artigo que comparou pacientes com AHD (n=31), AHE (n=32) e negAH (n=30), além de controles (n=101). Esse artigo investigou o impacto da atrofia hipocampal no perfil de linguagem em diferentes subtipos de ELT; avaliando a incidência e fatores preditivos de lateralização de linguagem, sua relação com o padrão de ativação da fMRI em regiões associadas à linguagem; comparação entre os grupos quanto ao padrão de ativação de linguagem e conectividade funcional, além da comparação do desempenho no teste de nomeação de Boston e sua correlação com o padrão de ativação da tarefa. Os resultados apontaram para frequência de LAL semelhante em todos os grupos e somente a dominância manual como preditor de dominância hemisférica para linguagem, porém, de forma distinta em cada grupo de acordo com as regiões de interesse. O padrão de ativação da linguagem e a análise entre regiões de interesse (ROI-to-ROI) apontaram pior desempenho do grupo AHE em relação aos grupos controle e negAH. A análise entre o giro frontal médio esquerdo e o cérebro todo (seed-based-voxel) mostrou que todos os grupos de pacientes apresentam conectividade funcional diminuída em relação aos controles, além de diferenças par a par entre os grupos de pacientes. O melhor desempenho em nomeação se correlacionou com maior ativação em áreas de linguagem nos grupos AHD e negAH. Este estudo concluiu que pacientes com AHE apresentaram pior desempenho em nomeação, ativação e conectividade funcional, seguidos pelos pacientes com AHD, enquanto os pacientes negAH apresentaram alterações discretas em comparação aos controles. Esta tese mostra que apesar dos vários estudos de fMRI sobre linguagem, novos trabalhos com diferentes metodologias e paradigmas são necessários para compreender melhor as alterações de linguagem em subtipos de ELTAbstract: Temporal lobe epilepsy is the most common type of epilepsy in adults and is also associated with cognitive comorbidities, such as memory and language impairments, especially in temporal lobe epilepsy (TLE). In this population, a higher incidence of people with atypical language lateralization (ALL) is expected; 20% against 5% of the healthy people. Some factors are pointed as predictors: manual dominance, left-hand familial history, as well as early insult and left hemisphere lesion. Language in these patients has been studied for decades. Lately functional magnetic resonance (fMRI) technique has been replacing the WADA test and has provided new methods and paradigms to study this function in vivo, including in healthy volunteers. Therefore, the objective of this study was to delineate the language aspects in TLE with left (LHA) and right (RHA) hippocampal atrophy and patients without hippocampal atrophy (nonAH), comparing them to controls. The results were set out in two manuscripts. The first, showed the translation of a well-established language fMRI paradigm based on semantic decision and comparison of two versions: easy and complex task in 24 healthy subjects. Both versions were effective, but the complex version produced more robust results for the evaluation of the language in our patients. Therefore, complex version was chosen to conduct the study with TLE patients. The second result was presented in the manuscript which compared patients with RHA (n=31), LHA (n=32), nonHA (n=30) and controls (n=101). In this paper analyzes were performed to investigate the impact of HA on language to obtain a profile of the language in different subtypes of TLE. Analyzes were conducted to acquire the incidence of language lateralization, predictive factors and correlation with fMRI activation pattern in regions associated with language; comparison between groups regarding language activation pattern and functional connectivity, as well as a comparison of performance on the Boston naming test and its correlation with the task activation pattern. The results pointed to a similar frequency of ALL in all groups and only manual dominance as a predictor of hemispheric dominance for language. However, each group was different according to the specific regions of interest. Language activation pattern and ROI-to-ROI analysis showed that LHA presented reduced activation compared with controls and nonHA groups. Seed-based-voxel analysis showed that all groups of patients had reduced functional connectivity in relation to controls, as well as differences among patients. The higher scores on naming performance was correlated with greater activation in language areas only in RHA and nonHA groups. We concluded that patients with LHA presented worse performance in naming, activation and functional connectivity, followed by RHA, and nonHA patients were more similar to controls. This thesis shows that despite of several language fMRI studies, further investigations using different methodologies and paradigms are necessary for better undestanding of language alterations in different TLE subtypesDoutoradoFisiopatologia MédicaDoutora em Ciências2012/05364-817229/12-0FAPESPCAPESBE

Lexical-semantic processing in bilingual children

Neue elektrophysiologische und bildgebende Messmethoden haben in den vergangenen Jahrzehnten neue Erkenntnisse über die neurofunktionalen Strukturen, die bilingualer Sprachverarbeitung zugrunde liegen, geliefert. Vor allem die Schnittstelle von Lexikon und Semantik lässt in der neurolinguistischen Forschung noch viele Fragen offen. Ziel der vorliegenden experimentellen Studie war es, die funktionalen Verarbeitungspfade und kortikalen Strukturen zu erkunden, die der lexikalischen und semantischen Analyse sprachlichen Inputs zugrundeliegen, sowie zu untersuchen, ob es gemeinsame Repräsentationen oder funktionale Interaktion in der Verarbeitung der beiden Sprachen im bilingualen Gehirn gibt. Dazu wurde eine experimentelle Studie mit 6- bis 7-jährigen Kindern durchgeführt: Mittels funktionaler Nahinfrarot-Spektroskopie wurde die kortikale Aktivierung während der Verarbeitung auditiv präsentierter deutscher und englischer Wörter gemessen. Die Abfolge der Stimuli folgte einem Priming-Design, wobei sowohl exakte Wiederholungen einzelner Wörter in einer Sprache, als auch Übersetzungen vom Englischen ins Deutsche und umgekehrt in der listenartigen Präsentationsabfolge der Wörter vorkamen. Die statistische Auswertung zeigte erhöhte Aktivierung für die Verarbeitung deutscher Wörter in linker temporaler Messposition, einen Priming-Effekt bei der Wiederholung von englischen Stimuli in temporalen Positionen bilateral, sowie Priming bei der Übersetzung Wörtern vom Englischen ins Deutsche in rechts-temporaler Position. Diese Ergebnisse werden im Bezug auf psycholinguistische Modelle interpretiert, und im Zusammenhang mit aktuellen Ergebnissen neurolinguistischer Studien diskutiert.During the last decades the continuously improving neuroimaging methods have shed some light on the neurofunctional architecture of the bilingual brain. Especially the organization of the bilingual lexicon and semantic system remains a major question in neurocognitive research. The aim of this study was to analyze the functional pathways and anatomical structures underlying lexical and semantic processing in the respective languages, and to test whether there are functional interconnections or common mental representations between the two languages in the bilingual brain. The experimental study with 6 to 7 year old German-English bilingual children used a repetition and translation priming design: The single words were presented auditorily in blocks of German and English. The presentation sequence contained exact repetitions of words in both languages respectively, as well as translated word pairs. The cortical activation was measured with near infrared spectroscopy (NIRS). The statistical analysis revealed greater activation for German words in left temporal position, a within-language priming effect for English in temporal positions bilaterally, and a cross-language priming effect from English to German items in right temporal position. The results are discussed in the light of psycholinguistic models of lexical-semantic processing and with respect to current neurophysiological research

Resting-state functional connectivity in the brain and its relation to language development in preschool children

Human infants have been shown to have an innate capacity to acquire their mother tongue. In recent decades, the advent of the functional magnetic resonance imaging (fMRI) technique has made it feasible to explore the neural basis underlying language acquisition and processing in children, even in newborn infants (for reviews, see Kuhl & Rivera-Gaxiola, 2008; Kuhl, 2010) . Spontaneous low-frequency (< 0.1 Hz) fluctuations (LFFs) in the resting brain have been shown to be physiologically meaningful in the seminal study (Biswal et al., 1995) . Compared to task-based fMRI, resting-state fMRI (rs-fMRI) has some unique advantages in neuroimaging research, especially in obtaining data from pediatric and clinical populations. Moreover, it enables us to characterize the functional organization of the brain in a systematic manner in the absence of explicit tasks. Among brain systems, the language network has been well investigated by analyzing LFFs in the resting brain. This thesis attempts to investigate the functional connectivity within the language network in typically developing preschool children and the covariation of this connectivity with children’s language development by using the rs-fMRI technique. The first study (see Chapter 2.1; Xiao et al., 2016a) revealed connectivity differences in language-related regions between 5-year-olds and adults, and demonstrated distinct correlation patterns between functional connections within the language network and sentence comprehension performance in children. The results showed a left fronto-temporal connection for processing syntactically more complex sentences, suggesting that this connection is already in place at age 5 when it is needed for complex sentence comprehension, even though the whole functional network is still immature. In the second study (see Chapter 2.2; Xiao et al., 2016b), sentence comprehension performance and rs-fMRI data were obtained from a cohort of children at age 5 and a one-year follow-up. This study examined the changes in functional connectivity in the developing brain and their relation to the development of language abilities. The findings showed that the development of intrinsic functional connectivity in preschool children over the course of one year is clearly observable and individual differences in this development are related to the advancement in sentence comprehension ability with age. In summary, the present thesis provides new insights into the relationship between intrinsic functional connectivity in the brain and language processing, as well as between the changes in intrinsic functional connectivity and concurrent language development in preschool children. Moreover, it allows for a better understanding of the neural mechanisms underlying language processing and the advancement of language abilities in the developing brain