Angel Tabullo

Event-related potential correlates of stimulus equivalence classes: A study of task order of the equivalence based priming probes with respect to the stimulus equivalence tests, and among the distinct trial types with each other

HighlightsTwo groups of healthy subjects received successive tasks in different order.Associations between pseudo‐words were selected by feedback.EEG was recorded during presentations of related and unrelated stimulus pairs.Response times to related stimuli were faster than those to unrelated stimuli.Two ERP waveforms were sensitive to the relatedness among the stimulus pairs. ABSTRACT This study investigates the influences of: 1) the task order of two stimulus equivalence classes (SEC) probes, and 2) the possible differences within the equivalence trial types. These factors were analyzed together on both behavioral and event‐related potentials (ERP) data. Two groups of normal subjects participated in two successive sessions. In the first session, all participants were trained in the baseline relations among visual stimuli (pseudo‐words). In the second session, one group performed the matching‐to‐sample (MTS) equivalence tests before the equivalence‐relatedness‐priming (EBRP) task, while the other group performed both tasks in reverse order. In the EBRP task related trial types included trained, symmetrical and equivalence relationships while the unrelated trial types included the same stimuli but without relationships. Event related potentials were recorded separately for related and unrelated conditions during the EBRP task. Results showed that response times to related trials were shorter than those to unrelated ones. At the electrophysiological level, two late waveforms were sensitive to the differences among the stimulus pairs of the EBRP task: Both waveforms were larger for the unrelated than the related conditions. Conversely, there were no main influences of the task order or of the trial types with each other. These results provide evidence that 1) the EBRP task exhibits priming effects among the SEC stimuli, 2) the behavioral and electrophysiological effects were similar regardless of whether the EBRP task was done before or after the MTS tests, and 3) there were no differences within the baseline and derived trial types in the EBRP task.

El papel de estructura argumental en el procesamiento de los compuestos verbo-nombre del español: Evidencias experimentales

Los compuestos verbo-nombre del espanol presentan la particularidad de carecer de un nucleo que aporte los rasgos morfologicos, de categoria o semantico-referenciales. El acceso al significado depende entonces de la relacion que mantienen los constituyentes entre si y no a partir de la identificacion de un elemento nuclear, como ocurre en compuestos que poseen un lexema referencial (telarana, bocacalle). Dentro del compuesto verbo-nombre, la relacion semantica que se establece entre los constituyentes no es unica. Si bien la estructura semantica prototipica responde al patron agente-paciente (cortacesped), existen otras posibilidades argumentales, como las relaciones locativas (pasacalle). El estudio realizado tuvo como objetivo determinar hasta que punto la estructura argumental proyectada por el verbo tiene una influencia en el procesamiento cognitivo de estas unidades. Primeramente, se llevo a cabo un juicio de aceptabilidad para asegurar que los estimulos se correspondieran con la realidad linguistica de los participantes del estudio experimental. A continuacion, se administro una prueba de decision lexica con compuestos que poseian distintos tipos de estructura argumental: (1) agente / paciente (algo que V a N, abrelatas), (2) agente / paciente menos prototipica (procesos metaforicos, chupasangre) y (3) locativos (lugar donde x hace V a N, guardamuebles). Los resultados muestran que los tiempos de decision (respuesta) ante compuestos locativos fueron significativamente mayores que ante los prototipicos. Este resultado no puede ser explicado por diferencias en longitud o frecuencia de los compuestos o sus constituyentes, por lo que parecen apoyar la hipotesis de que la estructura argumental juega un rol central en el procesamiento de estas palabras.

P32-13 A P600 component in an artificial grammar without semantics: an EEG study of structural violation type

Objective: The anterior N2 is a component of the event-related brain potential (ERP) elicited by visual novel stimuli. Previous studies reported that the stimuli which were subsequently viewed for longer periods of time elicited a larger anterior N2 than the stimuli viewed for shorter periods of time. This study examines how the complexity of visual materials affects the anterior N2 and subsequent viewing duration. Methods: Sixteen student participants viewed a total of 120 novel polygons with three different levels of complexity (12, 24, and 48 sides). They were asked to look at the figures one by one for as long as they wished. ERPs time-locked to the stimulus onset were averaged separately for three levels of complexity (12, 24, and 48 sides). In addition, ERPs were averaged separately for the stimuli viewed longer or shorter than the median viewing time at each complexity level by individual participants. Results: The more complex the stimuli, the larger the anterior negativity (N2) between 200 and 300 ms after stimulus onset. Moreover, the more complex the stimuli, the longer the viewing duration. However, when the stimuli were classified into longerand shorter-viewed figures, no difference in the anterior N2 amplitude was found. Conclusions: Results suggest that the anterior N2 is elicited by complex visual stimuli that require further attentional processing. As suggested in previous studies, this initial brain response can correlate with subsequent viewing duration. However, this study shows that there is no causal relationship between the anterior N2 and visual exploration.

229. An ERP study of category learning

dren of the same age. A NFB treatment was applied to 6 MMR children (IQ between 50 and 69), 6–11 years old (two boys) with normal neurological exam and abnormally higher theta/alpha ratio for their age. Positive reinforcement (tone of 500 Hz) was given when theta/alpha ratio was below a previously specified threshold. NFB training consisted of 30 sessions of 30 min each one. Significant changes in behaviour (IQ, Task of Attention Variables, and academic achievement) and EEG (reduction of theta Absolute Power and delta Relative Power, and increase of alpha and beta Relative Power) were observed. These changes were more apparent two months after NFB treatment. This NFB protocol is useful for the treatment of MMR children. This is the first report in MMR children using NFB.