N400 brain responses to spoken phrases paired with photographs of scenes: implications for visual scene displays in AAC systems.

Augmentative and alternative communication (AAC) systems are often implemented for individuals whose speech cannot meet their full communication needs. One type of aided display is called a Visual Scene Display (VSD). VSDs consist of integrated scenes (such as photographs) in which language concepts are embedded. Often, the representations of concepts on VSDs are perceptually similar to their referents. Given this physical resemblance, one may ask how well VSDs support development of symbolic functioning. We used brain imaging techniques to examine whether matches and mismatches between the content of spoken messages and photographic images of scenes evoke neural activity similar to activity that occurs to spoken or written words. Electroencephalography (EEG) was recorded from 15 college students who were shown photographs paired with spoken phrases that were either matched or mismatched to the concepts embedded within each photograph. Of interest was the N400 component, a negative deflecting wave 400 ms post-stimulus that is considered to be an index of semantic functioning. An N400 response in the mismatched condition (but not the matched) would replicate brain responses to traditional linguistic symbols. An N400 was found, exclusively in the mismatched condition, suggesting that mismatches between spoken messages and VSD-type representations set the stage for the N400 in ways similar to traditional linguistic symbols.

As origens da exclusão

Este artigo focaliza a "exclusão," um fenômeno demonstrado quando um participante vê uma matriz de estímulos de comparação previamente definidos, exceto um, em relação a um estímulo modelo falado. Quando um novo modelo não definido é ditado, os participantes selecionam, imediatamente, o item de comparação não definido, sem treino explícito. A exclusão tem atraído analistas do comportamento interessados em analisar comportamentos emergentes e/ou explorar o potencial do procedimento para ensinar comportamentos novos a pessoas com retardo mental severo. A importância dessa área de pesquisa tem crescido em anos recentes e o fenômeno tem sido reconhecido também por pesquisadores interessados no desenvolvimento da linguagem infantil e em cognição comparativa. Desde os estudos iniciais, na década de 70, aprendemos muito sobre exclusão; contudo, uma questão fundamental permanece sem resposta: qual a origem da exclusão? Por que praticamente todos os indivíduos demonstram exclusão na primeira oportunidade? Pesquisadores do Shriver Center for Mental Retardation (EUA) vem desenvolvendo uma série de delineamentos de sujeito como seu próprio controle, metodologicamente intrincados e inter-conectados, buscando responder a essas questões. Este artigo descreve o que foi obtido com indivíduos com retardo mental severo e com crianças com desenvolvimento típico.(AU)

This paper reports on "exclusion," a phenomenon demonstrated when a participant views an array of comparison stimuli, all but one of which has been defined in relation to a spoken sample stimulus (most often a dictated name). When a new undefined sample is spoken, participants immediately select the undefined comparison item without explicit training to do so. Exclusion has attracted interest from behavior analysts interested in analyzing emergent behavior and/or exploiting the potential of the procedure for teaching new behavior to persons with severe mental retardation. The importance of the research area has grown in recent years, as the phenomenon has been recognized also by researchers interested in the development of child language and comparative cognition. Since the first studies of exclusion, in the mid-1970s, we have learned much about the populations in which it appears, the types of stimuli that can enter into exclusion, and the contexts that affect performances. Yet a fundamental question remains unanswered: What is the origin of exclusion performance? Why do virtually all individuals demonstrate exclusion on the very first opportunity? A research group from the Shriver Center for Mental Retardation (USA) have recently developed a series of methodologically intricate, sometimes interconnected single-subject designs to answer these questions. This paper will describe work that has been completed thus far with individuals with severe mental retardation and a comparison group of typically developing children.(AU)