Effects of load and emotional state on EEG alpha-band power and inter-site synchrony during a visual working memory task.

Motivationally/emotionally engaging stimuli are strong competitors for the limited capacity of sensory and cognitive systems. Thus, they often act as distractors, interfering with performance in concurrent primary tasks. Keeping task-relevant information in focus while suppressing the impact of distracting stimuli is one of the functions of working memory (WM). Macroscopic brain oscillations in the alpha band (8-13 Hz) have recently been identified as a neural correlate of WM processing. Using electroencephalography, we examined the extent to which changes in alpha power and inter-site connectivity during a typical WM task are sensitive to load and emotional distraction. Participants performed a lateralized change-detection task with two levels of load (four vs. two items), which was preceded by naturalistic scenes rated either as unpleasant or neutral, acting as distractors. The results showed the expected parieto-occipital alpha reduction in the hemisphere contralateral to the WM task array, compared to the ipsilateral hemisphere, during the retention interval. Selectively heightened oscillatory coupling between frontal and occipital sensors was observed (1) during the retention interval as a function of load, and (2) upon the onset of the memory array, after viewing neutral compared to unpleasant distractors. At the end of the retention interval, we observed greater coupling during the unpleasant compared to the neutral condition. These findings are consistent with the notions that (1) representing more items in WM requires greater interconnectivity across cortical areas, and (2) unpleasant emotional distractors interfere with subsequent WM processing by disrupting processing during the encoding stage.

Order of stimulus presentation modulates interference in Stroop matching tasks: a reaction time study / Ordem de apresentação de estímulos modula interferências em testes Stroop-pareado: um estudo de tempo de reação / Orden de presentación de estímulos modula interferencias en testes Stroop-pareado: un estudio de tiempo de reacción

In the classic Stroop effect, the time spent to name the color of an incon­gruent stimulus (GREEN in blue) is longer than the time necessary to name the color of a congruent stimulus (BLUE in blue). In the “Stroop matching task”, volunteers are instructed to compare attributes of two stimuli, in which one of them is necessarily a Stroop stimulus. Our aim was to investigate whether the order of stimulus presentation can explain some contradictory results and reveal the imposition of high-order cognitive resources in conflict resolution. Our results confirmed that the strategy adopted in the task depended on the order in which stimuli were presented. In the “Stroop-Bar” order, using the interval between stimuli to solve the conflict inherent to the Stroop stimulus is possible, which is otherwise not possible in the “Bar-Stroop” order. However, these strategies cannot explain the discrepancy in the results reported in the literature.

No teste Stroop clássico, o tempo gasto para nomear a cor de um estímulo incongruente (VERDE em azul) é maior que o necessário para nomear a cor de um estímulo congruente (AZUL em azul). No teste Stroop-Pareado (Stroop matching task), voluntários são instruídos a comparar atributos de dois estímulos, sendo um deles, necessariamente, um estímulo Stroop. Nosso objetivo foi investigar se a ordem de apresentação dos estímulos pode explicar resultados contraditórios e revelar a imposição de recursos de alta ordem na solução de conflitos. Nossos resultados confirmam que a estratégia adotada para desempenhar a tarefa depende da ordem na qual os estímulos foram apresentados. Na ordem “Stroop-Barra”, é possível usar o intervalo entre os estímulos para solucionar o conflito inerente ao estímulo Stroop, o que não é possível na ordem “Barra-Stroop”. No entanto, essas estratégias não conseguem explicar a discrepância de resultados observados na literatura.

En la tarea Stroop clásica, el tiempo utilizado para nombrar el color de un estímulo incongruente (VERDE en azul) es más grande que lo necesario para nombrar el color de un estímulo congruente (AZUL en azul). En una tarea Stroop de comparación (Stroop matching task), voluntarios son instruidos a comparar atributos de dos estímulos, uno de ellos siendo necesariamente un estímulo Stroop. Nuestro objetivo fue investigar si el orden de presentación de los estímulos puede explicar algunos resultados contradictorios y revelar la imposición de recursos de alto orden en la solución­ de conflictos. Nuestros resultados confirman que la estrategia adoptada en la tarea depende del orden en el cual los estímulos fueran presentados. En el orden “Stroop-Barra” es posible utilizar el intervalo entre los estímulos para solucionar el conflicto inherente al estímulo Stroop, lo que no es posible en el orden “Barra-Stroop”. Sin embargo, esas estrategias no consiguen explicar la discrepancia de los resultados observados en la literatura.