Abstract

Spatial attention has been studied for over a half a century. Early behavioural work showed that attending to a location improves performance on a variety of tasks. Since then substantial progress has been made on understanding the neural mechanisms underlying these effects. This chapter reviews the neuroimaging literature, as well as related behavioural and single-cell physiology studies, on visual spatial attention. In particular, the chapter frames much of the work in the context of the biased competition theory of attention, which argues that a primary mechanism of attention is to bias competition among stimuli in the visual cortex in favour of an attended stimulus that, as a result, receives enhanced processing to guide behaviour. Accordingly, the authors have organized this chapter into two related sections. The first summarizes the effects of attention in the visual cortex and thalamus, the so-called ‘site’ of attention. The second explores the relationship between attention and fronto-parietal mechanisms which are thought to be the ‘source’ of the biasing signals exerted on the visual cortex.