Enhanced probe discrimination at the location of a colour singleton.

There is ample evidence to suggest that preparing to saccade to a location is sufficient to produce attentional shifts to this location. However, it is not clear whether engagement of the eye-movement system is also a necessary condition for any spatial shifts in attention. Recent neurophysiological data indicates that neurons in the frontal eye field (FEF) can select visual stimuli (a colour singleton) in the absence of a concurrently activated saccade plan in non-human primates (Juan et al. in Proc Natl Acad Sci USA 101:15541-15544, 2004), suggesting that saccade planning and visual selection are dissociable. However, it is still unclear whether the visual selection is accompanied by an attentional enhancement at the target location. To test this, we used a similar paradigm (i.e. an antisaccade task) with humans to the one employed by Juan and colleagues with monkeys. Our paradigm included a probe-discrimination task, which allowed us to test whether attentional facilitation is indeed observed at the location of the selected visual stimuli. Our results confirm that visual selection is accompanied by attentional facilitation.