Convergent and divergent fMRI responses in children and adults to increasing language production demands

In adults, patterns of neural activation associated with perhaps the most basic language skill—overt object naming—are extensively modulated by the psycholinguistic and visual complexity of the stimuli. Do children's brains react similarly when confronted with increasing processing demands, or they solve this problem in a different way? Here we scanned 37 children aged 7–13 and 19 young adults who performed a well-normed picture-naming task with 3 levels of difficulty. While neural organization for naming was largely similar in childhood and adulthood, adults had greater activation in all naming conditions over inferior temporal gyri and superior temporal gyri/supramarginal gyri. Manipulating naming complexity affected adults and children quite differently: neural activation, especially over the dorsolateral prefrontal cortex, showed complexity-dependent increases in adults, but complexity-dependent decreases in children. These represent fundamentally different responses to the linguistic and conceptual challenges of a simple naming task that makes no demands on literacy or metalinguistics. We discuss how these neural differences might result from different cognitive strategies used by adults and children during lexical retrieval/production as well as developmental changes in brain structure and functional connectivity

Semantic radical consistency and character transparency effects in Chinese: an ERP study

BACKGROUND: This event-related potential (ERP) study aims to investigate the representation and temporal dynamics of Chinese orthography-to-semantics mappings by simultaneously manipulating character transparency and semantic radical consistency. Character components, referred to as radicals, make up the building blocks used dur...postprin

Concordance of MEG and fMRI patterns in adolescents during verb generation

In this study we focused on direct comparison between the spatial distributions of activation detected by functional magnetic resonance imaging (fMRI) and localization of sources detected by magnetoencephalography (MEG) during identical language tasks. We examined the spatial concordance between MEG and fMRI results in 16 adolescents performing a three-phase verb generation task that involves repeating the auditorily presented concrete noun and generating verbs either overtly or covertly in response to the auditorily presented noun. MEG analysis was completed using a synthetic aperture magnetometry (SAM) technique, while the fMRI data were analyzed using the general linear model approach with random-effects. To quantify the agreement between the two modalities, we implemented voxel-wise concordance correlation coefficient (CCC) and identified the left inferior frontal gyrus and the bilateral motor cortex with high CCC values. At the group level, MEG and fMRI data showed spatial convergence in the left inferior frontal gyrus for covert or overt generation versus overt repetition, and the bilateral motor cortex when overt generation versus covert generation. These findings demonstrate the utility of the CCC as a quantitative measure of spatial convergence between two neuroimaging techniques

The Cerebellum\u27s Relationship to Language Function Following Perinatal Stroke

While recent studies have demonstrated the association between the cerebellum and higher-order cognitive functioning, it is still unclear how volumetric differences of specific regions of interests within the cerebellum across typical and atypical development are related to language function. We have done so by measuring the volume of cerebellar subregions of healthy controls, and compared the volume to behavioral measures of language function. We then followed with an analysis of the cerebellum’s relationship to language function following perinatal stroke, which provides us with a greater knowledge of the impact of a cortical injury on cerebellar development and the cognitive outcomes of such changes by again measuring and comparing the volume of cerebellar subregions to language measures. We report several novel findings that contribute to the growing understanding of the cerebellum’s relationship to language function. We found that greater right laterality of lobules IV and VIIb predicted performance on expressive language measures in typical development. We also found that following an early injury to the cerebral cortex\u27s left hemisphere, there was a bilateral association of cerebellar lobules to language measures. Specifically, we found greater right laterality of the cerebellar cortex, lobule IV, and Crus I predicted higher scores on the Expressive Vocabulary Test. While greater left lateralization of lobule VI predicted expressive language and lobule VIIIa predicted grammatical judgment, especially early in development, and greater left lateralization of lobule IX predicted receptive vocabulary. Implications of the findings of volumetric association to language function and poststroke development within the cerebellum are discussed

Linking sentence production and comprehension: The neural mechanisms underlying production and comprehension control processes

This thesis investigated the relationship between sentence production and comprehension. A combination of behavioural and neuroimaging techniques were used to examine the extent to which sentence production and comprehension engage common or distinct mechanisms, with specific focus on the processes engaged by semantic/syntactic competition. Behavioural studies in Chapter 2 indicated that high-competition cases were more difficult to understand and produce than low-competition cases, and that difficulty varied as a function of the number of alternative associations entertained during performance in both tasks. In Chapter 3, an fMRI study indicated that production and comprehension shared a common competition mechanism within left inferior frontal gyrus (LIFG). However, they engage distinctive networks that interact with LIFG, with production eliciting a larger network including areas involved in sentence planning and memory retrieval. Further asymmetries across tasks were revealed in Chapter 4, in which behavioural results and neural networks were compared across adults and adolescents. This study also demonstrated the occurrence of shifts in the neural networks involved in competition resolution throughout development, thereby providing a strong link between poor behavioural performance and the underdevelopment of pre-frontal inhibitory mechanisms in adolescents. Chapter 5 used an improved experimental paradigm from that in Chapters 3 and 4. The results showed that production elicits more activity than comprehension in the dorsal language route thus confirming the engagement of task-specific control processes. Interestingly, this study also revealed a common area of LIFG involved in both tasks, but also differences within LIFG, suggesting the possibility of task-specific circuitry. Together, the findings suggest that production and comprehension share fronto-temporal areas that store and manage abstract linguistic associations between words and structures. However, they differ in the manner in which linguistic information is used, as is evident by the recruitment of distinct networks. Implications for models of language processing are discussed

Mapping cortical activations underlying covert and overt language production using high-density diffuse optical tomography

Gold standard neuroimaging modalities such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and more recently electrocorticography (ECoG) have provided profound insights regarding the neural mechanisms underlying the processing of language, but they are limited in applications involving naturalistic language production especially in developing brains, during face-to-face dialogues, or as a brain-computer interface. High-density diffuse optical tomography (HD-DOT) provides high-fidelity mapping of human brain function with comparable spatial resolution to that of fMRI but in a silent and open scanning environment similar to real-life social scenarios. Therefore, HD-DOT has potential to be used in naturalistic settings where other neuroimaging modalities are limited. While HD-DOT has been previously validated against fMRI for mapping the neural correlates underlying language comprehension and covert (i.e., silent ) language production, HD-DOT has not yet been established for mapping the cortical responses to overt (i.e., out loud ) language production. In this study, we assessed the brain regions supporting a simple hierarchy of language tasks: silent reading of single words, covert production of verbs, and overt production of verbs in normal hearing right-handed native English speakers (n = 33). First, we found that HD-DOT brain mapping is resilient to movement associated with overt speaking. Second, we observed that HD-DOT is sensitive to key activations and deactivations in brain function underlying the perception and naturalistic production of language. Specifically, statistically significant results were observed that show recruitment of regions in occipital, temporal, motor, and prefrontal cortices across all three tasks after performing stringent cluster-extent based thresholding. Our findings lay the foundation for future HD-DOT studies of imaging naturalistic language comprehension and production during real-life social interactions and for broader applications such as presurgical language assessment and brain-machine interfaces

Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

In congenital blindness, the occipital cortex responds to a range of nonvisual inputs, including tactile, auditory, and linguistic stimuli. Are these changes in functional responses to stimuli accompanied by altered interactions with nonvisual functional networks? To answer this question, we introduce a data-driven method that searches across cortex for functional connectivity differences across groups. Replicating prior work, we find increased fronto-occipital functional connectivity in congenitally blind relative to blindfolded sighted participants. We demonstrate that this heightened connectivity extends over most of occipital cortex but is specific to a subset of regions in the inferior, dorsal, and medial frontal lobe. To assess the functional profile of these frontal areas, we used an n-back working memory task and a sentence comprehension task. We find that, among prefrontal areas with overconnectivity to occipital cortex, one left inferior frontal region responds to language over music. By contrast, the majority of these regions responded to working memory load but not language. These results suggest that in blindness occipital cortex interacts more with working memory systems and raise new questions about the function and mechanism of occipital plasticity.David & Lucile Packard FoundationNational Science Foundation (U.S.). Graduate Research Fellowship Progra

A ciência da leitura e a produção acadêmica: caminhos trilhados

Linguistics focuses on the different phenomena of language. In macrolinguistics areas, there is Psycholinguistics. This subfield researches (de)coding processes of messages with verbal codes. Thus, one of its influential fields of activity is reading. Reading is one of the most complex information processing tasks. It begins with the graphemes decoding and it finishes with the text comprehension. Regarding the assessment of reading, there are several exams and large-scale tests, such as Pisa, Saeb (Aneb and Anresc/Prova Brasil), ENEM. Alarming statistics come with the indicators from these evaluative instruments. There are, among Brazilians, low levels of reading comprehension and marked functional illiteracy rate. Therefore, this study aimed to research what scientific communication has shared in terms of knowledge about reading. Specifically, the objectives were synthesize, considering the psycholinguistic approach of reading research, studies and research with the most recurrent theme in the reading field evidenced from the electronic communication, in order to investigate the dimensions and limitations of knowledge about this subject. For this, through WebQualis system, Qualis A1 and A2 scientific journals with electronic format and with focuses/scopes related to reading from the areas of (1) Language Arts/Linguistics, (2) Psychology and (3) Education were selected. With the selected journals and through Capes Journals Portal, all their volumes and issues from 2011 to 2015 were analyzed. With this, scientific articles related to reading were mapped. With the mapped articles abstracts, the recurrent themes in reading in the scientific production were observed. Finally, with the full articles that had the recurrent theme, the researches results were integrated, synthesizing and pondering about them. With a critical-reflexive assessment of the data, relevant information was found. First, on one hand, it was noted that the reading has achieved a stable and upward space through the electronic communication. On the other one, it was checked that the contributions of Psychology have a great influence in reading and comprehension research. Second, it was shown that the most frequent theme in electronic productions is comprehension. Finally, with the synthesis, it was found that, increasingly, comprehension topics related to reading neurobiological aspects were empirical and directly investigated. In addition, there are several studies that propose reading teaching methods as well as strategies for improving the comprehension, including the use of TICs. Moreover, it was found that many research results are limited. This is because the comprehension involves several components – cognitive processes and skills. Researches often focus attention on one or the other component of it only, and each research fixes a specific methodology design and that vary considerabably. Regarding the assessment of reading, many of the methodological apparatus tasks evaluate only the product of comprehension and not its process. In other words, built mental representations are evaluated and not how the encoding of this text occurred. Therefore, in short, both the researches advancement in the comprehension field and several limitations were observed.A Linguística atém-se aos mais diferentes fenômenos da língua(gem). Nos domínios macrolinguísticos, há a Psicolinguística. Essa subárea tem como foco de investigação os processos de (de)codificação de mensagens de códigos verbais. Assim, um de seus influentes campos de atuação é o de leitura. A leitura é uma das tarefas de processamento de informações mais complexas. Ela tem como princípio a decodificação grafêmica e como fim a compreensão textual. Em relação à avaliação da leitura, existem diversos testes e provas em larga escala, como o Pisa, o Saeb (Aneb e Anresc/Prova Brasil), o ENEM. Com os indicadores desses instrumentos avaliativos, vêm estatísticas alarmantes. Há, entre os brasileiros, baixos níveis de compreensão leitora e acentuado índice de analfabetismo funcional. Por conseguinte, este trabalho pretendeu investigar o que a comunicação científica tem compartilhado em termos de conhecimento sobre leitura. Especificamente, objetivou-se sintetizar, considerando a abordagem psicolinguística de investigação da leitura, estudos e pesquisas cuja temática evidenciada da comunicação eletrônica fosse a mais recorrente no campo da leitura, a fim de investigar dimensões e limitações do conhecimento a respeito dessa temática. Para isso, selecionaram-se, por meio do sistema WebQualis, periódicos científicos Qualis A1 e A2 em formato eletrônico e com focos/escopos relacionados à leitura, das áreas de (1) Letras/Linguística, (2) Psicologia e (3) Educação. Com os periódicos selecionados e por meio do Portal de Periódicos Capes, analisaram-se todos os seus volumes e números de 2011 a 2015, a fim de mapear artigos científicos com assunto em leitura. Com os resumos dos artigos mapeados, evidenciaram-se temáticas mais recorrentes na produção científica em leitura. Por fim, dos artigos completos cuja temática era a mais recorrente, integraram-se resultados das pesquisas, fazendo-se uma análise, com fins de síntese e reflexão. Da apreciação crítico-reflexiva dos dados, constataram-se relevantes informações. Em primeiro lugar, de um lado, observou-se que a leitura tem conquistado um estável e ascendente espaço em meio à comunicação eletrônica. De outro, demonstrou-se que contribuições da Psicologia têm forte influência na pesquisa de leitura e compreensão. Em segundo, evidenciou-se que a compreensão é a temática mais frequente nas produções eletrônicas. Por fim, com a síntese, constatou-se que, cada vez mais, se investiga empírica e diretamente facetas da compreensão em relação às bases neurobiológicas da leitura. Igualmente, há diversas pesquisas que propõem metodologias de ensino da leitura, bem como estratégias para a melhoria da compreensão, incluindo a utilização das TICs. Além disso, concluiu-se que muitos resultados de pesquisas são limitados. Isso porque a compreensão envolve diversos componentes – processos cognitivos e habilidades. E as pesquisas, muitas vezes, apenas focam a atenção em um ou em outro componente, além de definirem específicos e variados designs de metodologia. Em relação à avaliação da leitura, muitas das tarefas do aparato metodológico das pesquisas apenas avaliam o produto da compreensão e não o seu processo. Ou seja, avaliam-se representações mentais construídas e não como ocorreu a codificação desse texto na mente do leitor. Por conseguinte, em suma, tanto o avanço de pesquisas no campo de compreensão quanto, também, diversas limitações ficaram evidentes

Neuroimaging investigations of language to aid paediatric neurosurgical decision making

Childhood onset epilepsy can have a profound effect on cognitive, emotional and behavioural development. As such, early intervention is crucial. Approximately 25-50% of children with epilepsy show resistance to medication however. For these children, neurosurgical intervention may be considered. The decision for surgery is a multi-disciplinary process, including functional Magnetic Resonance Imaging (fMRI) to assess the risk posed by surgery to language. Based on feasibility and behavioural pilot studies, I developed an fMRI task panel optimised for pre-surgical investigations of language in children. This task panel maps different language systems (word retrieval, sentence generation, auditory comprehension and reading comprehension) and localises critical language functions (semantic and syntactic processing). I validated this task panel in healthy children (N=43, 5-16 years). This included assessments of scan quality, comparison of methods for artefact repair, and definition of typical activation patterns. I also piloted the new task panel in a representative sample of children with epilepsy, who were being considered for surgery (N=13, aged 5-16 years). Patient case studies are reported to highlight methodological challenges associated with localisation of critical language regions on an individual basis. Finally, I present experimental analyses which highlight the importance of the ventral system to semantic processing. Activation in this network was reduced in children with epilepsy and predicted language outcome. Further investigation showed prolonged development of specific nodes within this system, supporting multimodal semantic processing (independent of effort and performance accuracy). These regions included ventral occipito-temporal cortex, whose role in semantic processing has so far been underappreciated in the developmental literature. These analyses provide evidence for a core language system, which may be crucial for post-surgical language outcome. The findings from this thesis contribute towards extending and improving the role of fMRI in the surgical decision-making process, with the potential for improving long term outcome. They also contribute to models of typical and atypical language development