Changes in neural responses based on spatial attention have been demonstrat
ed in many areas of visual cortex(1-4), indicating that the neural correlat
e of attention is an enhanced response to stimuli at an attended location a
nd reduced responses to stimuli elsewhere. Here we demonstrate non-spatial,
feature-based attentional modulation of visual motion processing, and show
that attention increases the gain of direction-selective neurons in visual
cortical area MT without narrowing the direction-tuning curves. These find
ings place important constraints on the neural mechanisms of attention and
we propose to unify the effects of spatial location, direction of motion an
d other features of the attended stimuli in a 'feature similarity gain mode
l' of attention.