The time course of language production as revealed by pattern classification of MEG sensor data

Language production involves a complex set of computations, from conceptualization to articulation, which are thought to engage cascading neural events in the language network. However, recent neuromagnetic evidence suggests simultaneous meaning-to-speech mapping in picture naming tasks, as indexed by early parallel activation of frontotemporal regions to lexical semantic, phonological, and articulatory information. Here we investigate the time course of word production, asking to what extent such “earliness” is a distinctive property of the associated spatiotemporal dynamics. Using MEG, we recorded the neural signals of 34 human subjects (26 males) overtly naming 134 images from four semantic object categories (animals, foods, tools, clothes). Within each category, we covaried word length, as quantified by the number of syllables contained in a word, and phonological neighborhood density to target lexical and post-lexical phonological/phonetic processes. Multivariate pattern analyses searchlights in sensor space distinguished the stimulus-locked spatiotemporal responses to object categories early on, from 150 to 250 ms after picture onset, whereas word length was decoded in left frontotemporal sensors at 250-350 ms, followed by the latency of phonological neighborhood density (350-450 ms). Our results suggest a progression of neural activity from posterior to anterior language regions for the semantic and phonological/phonetic computations preparing overt speech, thus supporting serial cascading models of word productio

The Spatial and Temporal Signatures of Word Production Components: A Critical Update

In the first decade of neurocognitive word production research the predominant approach was brain mapping, i.e., investigating the regional cerebral brain activation patterns correlated with word production tasks, such as picture naming and word generation. Indefrey and Levelt (2004) conducted a comprehensive meta-analysis of word production studies that used this approach and combined the resulting spatial information on neural correlates of component processes of word production with information on the time course of word production provided by behavioral and electromagnetic studies. In recent years, neurocognitive word production research has seen a major change toward a hypothesis-testing approach. This approach is characterized by the design of experimental variables modulating single component processes of word production and testing for predicted effects on spatial or temporal neurocognitive signatures of these components. This change was accompanied by the development of a broader spectrum of measurement and analysis techniques. The article reviews the findings of recent studies using the new approach. The time course assumptions of Indefrey and Levelt (2004) have largely been confirmed requiring only minor adaptations. Adaptations of the brain structure/function relationships proposed by Indefrey and Levelt (2004) include the precise role of subregions of the left inferior frontal gyrus as well as a probable, yet to date unclear role of the inferior parietal cortex in word production

MRI neuroimaging: language recovery in adult aphasia due to stroke

Thesis (Ph.D.)--Boston UniversityThis research focuses on the contribution of magnetic resonance imaging (MRI) to understanding recovery and treatment of aphasia in adults who have suffered a stroke. There are three parts. Part 1 presents the feasibility of the application of an overt, picture-naming, functional MRI (fMRI) paradigm to examine neural activity in chronic, nonfluent aphasia (four mild-moderate and one severe nonfluent/global patient). The advantages and disadvantages of an overt, object picture-naming, fMRI block-design paradigm are discussed. An overt naming fMRI design has potential as a method to provide insight into recovery from adult aphasia including plasticity of the brain after left hemisphere stroke and response to treatment. Part 2 uses the overt naming fMRI paradigm to examine changes in neural activity (neural plasticity) after a two-week series of repetitive transcranial magnetic stimulation (rTMS) treatments to improve picture naming in chronic nonfluent aphasia. An overview of rTMS and rationale for use of rTMS as a clinical treatment for aphasia is provided. Patterns of fMRI activation are examined in two patients with chronic nonfluent aphasia following a two-week series of 1 Hz rTMS treatments to suppress the right pars triangularis portion of the right hemisphere, Broca's homologue. One patient responded well, and the other did not. Differences in fMRI activation in response to the rTMS treatment for the two patients may be due to differences in the patients' lesion sites and extent of damage within each lesion site. Part 3 examines the area of the corpus callosum (CC) in 21 chronic nonfluent aphasia patients and 13 ageequivalent controls using structural MRI. Understanding brain morphology and potential atrophy of the CC in chronic stroke patients may shed light on alterations in the interhemispheric dynamics after stroke, especially patterns of brain reorganization during post-stroke language recovery. A decrease in interhemispheric connections has implications for mechanisms of language recovery and potential success with specific treatment methods. Future directions of both structural and functional neuroimaging to study language recovery in adult aphasia are discussed

Response-Locked Brain Dynamics of Word Production

International audienceThe cortical regions involved in the different stages of speech production are relatively well-established, but their spatio-temporal dynamics remain poorly understood. In particular, the available studies have characterized neural events with respect to the onset of the stimulus triggering a verbal response. The core aspect of language production, however, is not perception but action. In this context, the most relevant question may not be how long after a stimulus brain events happen, but rather how long before the production act do they occur. We investigated speech production-related brain activity time-locked to vocal onset, in addition to the common stimulus-locked approach. We report the detailed temporal interplay between medial and left frontal activities occurring shortly before vocal onset. We interpret those as reflections of, respectively, word selection and word production processes. This medial-lateral organization is in line with that described in non-linguistic action control, suggesting that similar processes are at play in word production and non-linguistic action production. This novel view of the brain dynamics underlying word production provides a useful background for future investigations of the spatio-temporal brain dynamics that lead to the production of verbal responses. Citation: Riès S, Janssen N, Burle B, Alario F-X (2013) Response-Locked Brain Dynamics of Word Production. PLoS ONE 8(3): e58197

Modulation of Brain Activity after Learning Predicts Long-Term Memory for Words

The acquisition and maintenance of new language information, such as picking up new words, is a critical human ability that is needed throughout the life span. Most likely you learned the word “blog” quite recently as an adult, whereas the word “kipe,” which in the 1970s denoted stealing, now seems unfamiliar. Brain mechanisms underlying the long-term maintenance of new words have remained unknown, albeit they could provide important clues to the considerable individual differences in the ability to remember words. After successful training of a set of novel object names we tracked, over a period of 10 months, the maintenance of this new vocabulary in 10 human participants by repeated behavioral tests and magnetoencephalography measurements of overt picture naming. When naming-related activation in the left frontal and temporal cortex was enhanced 1 week after training, compared with the level at the end of training, the individual retained a good command of the new vocabulary at 10 months; vice versa, individuals with reduced activation at 1 week posttraining were less successful in recalling the names at 10 months. This finding suggests an individual neural marker for memory, in the context of language. Learning is not over when the acquisition phase has been successfully completed: neural events during the access to recently established word representations appear to be important for the long-term outcome of learning.Peer reviewe

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

Eficácia de uma abordagem integrada de intervenção neurolinguística na afasia progressiva primária

In the past few years, primary progressive aphasia has been acknowledged as an emerging field of practice. Considered a neurodegenerative-based syndrome, primary progressive aphasia requires a singular pathway that addresses the associated characteristics of the syndrome. Among the several treatment approaches that have been investigated, behavioural interventions seem to offer some promise. Despite evidence suggests that intervention should capitalize on spared language abilities and improve communication performance to increase functioning levels, a large number of interventions has focused on remediating impaired skills. Accordingly, the present work aimed to design, implement and evaluate the effects of an intervention that targets the maintenance of a core vocabulary and the training of communication strategies along with the use of augmentative and alternative communication devices. Particularly, this case report aimed to analyse the effect of a neurolinguistic intervention on naming performance for trained and untrained words, and quality of life. Two patients diagnosed with primary progressive aphasia participated in this study that took place over the period of five months. Data collection occurred before intervention, during intervention every two-week interval, immediately after the intervention and one month after treatment was complete. Outcome measures consisted of formal and standardized instruments, adapted and validated to Portuguese population. The intervention approach used in this study produced a limited but promising impact on participants. One participant improved naming accuracy and both participants retained therapy gains. Several methodological aspects limited the outcomes representativeness and generalization of conclusions to clinical practice, namely the reduced number of participants, the presence of different diagnosis and the design. This study provides preliminary data on the effects of combined intervention approaches and their impact on patients’ quality of life. The involvement of close family members on therapy sessions is highlighted as beneficial.A afasia progressiva primária tem sido reconhecida como uma área de intervenção emergente nos últimos anos. Considerando-se uma síndrome de origem neurodegenerativa, a afasia progressiva primária requer uma resposta diferenciada que vá ao encontro das características inerentes a esta condição. Várias abordagens de intervenção têm sido exploradas, de entre as quais se destacam as intervenções comportamentais, pelos resultados promissores que têm oferecido. Embora se defenda cada vez mais que a intervenção se deva focar na manutenção de competências linguísticas residuais e na maximização das competências comunicativas, no sentido de aumentar os níveis de funcionalidade da pessoa, grande parte das intervenções têm valorizado a reaprendizagem de competências perdidas. Neste sentido, o presente trabalho teve como principal objetivo desenhar, implementar e avaliar os efeitos de uma intervenção que promove a manutenção de um vocabulário funcional e o treino de estratégias comunicativas a par da utilização de meios de comunicação aumentativa e alternativa. Especificamente, este estudo de caso visou analisar o efeito de uma intervenção neurolinguística na capacidade de nomeação de palavras treinadas e não treinadas, e qualidade de vida. Dois pacientes diagnosticados com afasia progressiva primária participaram no estudo que teve uma duração total de cinco meses. Foram recolhidos dados antes da intervenção, durante a intervenção a cada duas semanas, imediatamente após a intervenção e um mês após o fim do tratamento. Para tal foram utilizados instrumentos de medida formais e estandardizados, adaptados e aferidos à população portuguesa. A abordagem de intervenção implementada teve um impacto limitado, mas promissor, nos participantes. Registou-se uma melhoria das competências de nomeação num dos casos, e manutenção de competências adquiridas em ambos os casos. Vários fatores metodológicos limitaram a representatividade dos resultados obtidos e aplicabilidade das conclusões à prática clínica, nomeadamente o reduzido número de participantes, a heterogeneidade no diagnóstico e o desenho do estudo. Os resultados deste estudo providenciam dados preliminares acerca do efeito de abordagens integradas de intervenção e impacto na qualidade de vida das pessoas com afasia progressiva primária. Destaca-se a importância do envolvimento de familiares diretos nas sessões terapêuticas, como fator facilitador.Programa Doutoral em Psicologi