Visual search and single-cell electrophysiology of attention: Area MT, from sensation to perception

Evolution has equipped the visual system of primates with sophisticated features that allow the concentration of neuronal processing resources on a small subset of the incoming information. Here we review evidence, concentrating on recordings from area MT in the extrastriate cortex of macaque monkeys trained to perform visual tasks, that these “bottom-up” filtering processes are tightly integrated with “top-down” attentional mechanisms that together they create an integrated saliency map. This topographic representation emphasizes behavioural relevance of the sensory input at the expense of an accurate and complete representation of the external world.