Top-down Mechanisms for Working Memory and Attentional Processes

Acknowledgements We wish to thank David Sturman for assistance in the preparation of the manuscript. Introduction Maintaining information in working memory (WM), such as when we rehearse the route to a restaurant, as well as directing attention, such as when we search for a familiar face in the crowd, constitute fundamental cognitive capabilities of the primate brain. Both activities are considered " top-down " , as they depend on goal-directed processes that rely on previous knowledge, and not incoming sensory stimulation. Top-down processes should be contrasted to " bottom-up " ones, such as the deployment of attention in reaction to a sudden movement in the periphery of the visual field, which is a sensory-driven, reflexive process. Understanding the neural bases of top-down control involved in WM and visual attention, is among the most challenging goals of cognitive neuroscience. In this chapter, we will review neuroimaging studies that have investigated this question in the past decade or so. The picture emerging from this line of research points to considerable overlap between the neural substrates that control WM and those that control attention. At the same time, there is growing evidence that the control structures for attention differ according to the type of attentive process, in that goal-directed and reflexive attention appear to be mediated by separable networks of frontal and parietal regions.