Imagine you are watching a fox running through a dense forest. To keep track of him as he disappears and reappears, you may focus on all things that are reddish and moving to the right. Feature-based attention selectively enhances the processing of a particular visual feature value within a dimension, such as a particular color or motion direction. In the context of feature-based attention to motion directions specifically, the underlying neural mechanisms have been explored with electrophysiological recordings from the middle temporal area in monkeys (Treue and Martinez Tmjillo, 1999; Martinez-TrujlUo and Treue, 2004). These previous studies led to the formulation of the feature-similarity gain model of up-modulations of activity in neurons that prefer the attended feature value and down-modulations of activity in neurons that do not prefer the attended feature value. These modulations enhance the population response to stimuli with the attended direction. Interestingly, the effect spreads involuntarily across space: feature-based modulations occur for cells with receptive fields at distant, task-irrelevant locations.
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