Attention to locations and features: different top-down modulation of detector weights.

It is well known that attention improves the visibility of a target. In this study, we examined the effect of attention on the selectivity profile for a target. We used a masking technique to measure the tuning function for detecting a target while cueing either its orientation or its location. In the presence of an orientation mask, uncued thresholds were maximally elevated with a parallel mask and decreased with increasing mask orientation from the target. The presence of a cue reduced the masking effect but the shape of the function was cue-specific: The orientation cue consistently improved thresholds at the target orientation, whereas the location cue typically improved thresholds at all orientations relative to the function measured in the absence of attention. The selective versus overall increase of sensitivity observed in our study may be due to differences in the weighting of individual detectors that determine the behavioral tuning function in the two cueing conditions.