RESUMEN
The semantic knowledge stored in our brains can be accessed from different stimulus modalities. For example, a picture of a cat and the word "cat" both engage similar conceptual representations. While existing research has found evidence for modality-independent representations, their content remains unknown. Modality-independent representations could be semantic, or they might also contain perceptual features. We developed a novel approach combining word/picture cross-condition decoding with neural network classifiers that learned latent modality-independent representations from MEG data (25 human participants, 15 females, 10 males). We then compared these representations to models representing semantic, sensory, and orthographic features. Results show that modality-independent representations correlate both with semantic and visual representations. There was no evidence that these results were due to picture-specific visual features or orthographic features automatically activated by the stimuli presented in the experiment. These findings support the notion that modality-independent concepts contain both perceptual and semantic representations.
Asunto(s)
Magnetoencefalografía , Estimulación Luminosa , Semántica , Humanos , Femenino , Masculino , Adulto , Adulto Joven , Estimulación Luminosa/métodos , Percepción Visual/fisiología , Formación de Concepto/fisiología , Encéfalo/fisiología , Mapeo Encefálico , Reconocimiento Visual de Modelos/fisiologíaRESUMEN
To what extent does language production activate cross-modal conceptual representations? In picture naming, we view specific exemplars of concepts and then name them with a label, like "dog". In overt reading, the written word does not express a specific exemplar. Here we used a decoding approach with magnetoencephalography (MEG) to address whether picture naming and overt word reading involve shared representations of superordinate categories (e.g., animal). This addresses a fundamental question about the modality-generality of conceptual representations and their temporal evolution. Crucially, we do this using a language production task that does not require explicit categorization judgment and that controls for word form properties across semantic categories. We trained our models to classify the animal/tool distinction using MEG data of one modality at each time point and then tested the generalization of those models on the other modality. We obtained evidence for the automatic activation of cross-modal semantic category representations for both pictures and words later than their respective modality-specific representations. Cross-modal representations were activated at 150 ms and lasted until around 450 ms. The time course of lexical activation was also assessed revealing that semantic category is represented before lexical access for pictures but after lexical access for words. Notably, this earlier activation of semantic category in pictures occurred simultaneously with visual representations. We thus show evidence for the spontaneous activation of cross-modal semantic categories in picture naming and word reading. These results serve to anchor a more comprehensive spatio-temporal delineation of the semantic feature space during production planning.
Asunto(s)
Lenguaje , Semántica , Animales , Perros , LecturaRESUMEN
During language comprehension, the brain processes not only word meanings, but also the grammatical structure-the "syntax"-that strings words into phrases and sentences. Yet the neural basis of syntax remains contentious, partly due to the elusiveness of experimental designs that vary structure independently of meaning-related variables. Here, we exploit Arabic's grammatical properties, which enable such a design. We collected magnetoencephalography (MEG) data while participants read the same noun-adjective expressions with zero, one, or two contiguously-written definite articles (e.g., 'chair purple'; 'the-chair purple'; 'the-chair the-purple'), representing equivalent concepts, but with different levels of syntactic complexity (respectively, indefinite phrases: 'a purple chair'; sentences: 'The chair is purple.'; definite phrases: 'the purple chair'). We expected regions processing syntax to respond differently to simple versus complex structures. Single-word controls ('chair'/'purple') addressed definiteness-based accounts. In noun-adjective expressions, syntactic complexity only modulated activity in the left posterior temporal lobe (LPTL), ~ 300 ms after each word's onset: indefinite phrases induced more MEG-measured positive activity. The effects disappeared in single-word tokens, ruling out non-syntactic interpretations. In contrast, left anterior temporal lobe (LATL) activation was driven by meaning. Overall, the results support models implicating the LPTL in structure building and the LATL in early stages of conceptual combination.
Asunto(s)
Comprensión/fisiología , Semántica , Lóbulo Temporal/fisiología , Adulto , Mapeo Encefálico/métodos , Femenino , Humanos , Magnetoencefalografía , Masculino , Lectura , Escritura , Adulto JovenRESUMEN
Reading plays an essential role in our everyday lives. The aim of this study is to investigate how letters are represented in the brain using the unique characteristics of the Arabic language, which can be written with 2 different scripts. The hypothesis proposed is that the processing of script is sound based: Phonology is what determines letter identity. Using a forward-masked priming paradigm, we showed that Latin-script primes facilitated the recognition of subsequent Arabic-script targets which differed in orthography but shared phonology, thus suggesting a common level of phonological processing. In addition, semantic priming effects were controlled for. The findings thus confirmed our hypothesis and showed that letters that represent the same sound are processed similarly.
Asunto(s)
Lenguaje , Psicolingüística , Lectura , Escritura , Femenino , Humanos , Líbano , Masculino , Tiempo de Reacción , Percepción Visual , Adulto JovenRESUMEN
Early childhood mental health programs are vital for the current and future mental health and brain development of infants, toddlers, and preschoolers. Founded in 2014, Safe Start is the only early childhood mental health program in Beirut, Lebanon. It aims at being the prototype of such services at the national level. A retrospective analysis of the outcomes of the first year of operations has resulted in important findings about the age of the participants, their diagnoses, previous therapies that the participants have undergone, types of referrals recommended, and the number of participants who were lost to follow-up. This first analysis pointed at the need for more in-depth research to encompass the gaps and benefits of such services. It shows the pivotal importance of designing awareness strategies about the importance of early childhood mental health services and care; to move from a diagnostic seeking behavior to commitment to psychotherapy and follow-up interventions.