Attention acts to suppress goal-based conflict under high competition

It is known that w hen multiple stimuli are present, top - down attention selectively enhances the neural signal in the visual cortex for task - relevant stimuli, but this has been tested only under conditions of minimal competition of visual attention . Here w e show during high competition, t hat is, two s timuli in a shared rec e ptive field possessing o pposing modulatory goals, top - down attention suppress es both task - relevant and irrelevant neural signals within 100 ms of stimuli onset. This non - selective engagement of top - down attentional resources serves to reduce the feedforward signal representing irrelevant stimuli . It is well established that attention modulates visual processing in extrastriate cortex (Tsotsos et al., 1995) . Strong evidence for the mutual competition theory, acting at the level of the receptive fields in the extrastriate cortex, suggests that local neuronal activity representing simultaneous stimuli result in suppression of these representations at the level of the receptive field (Moran and Desimone, 1985; Reynolds et al., 1999; Kastner and Ungerleider, 2001) .