Figure 1. Experiment design.

A series of drifting Gabor stimuli was flashed at each of three locations: two within the receptive field of the MT neuron being recorded and one outside the receptive field. The two stimuli inside the receptive field moved in the cell's preferred and null directions, the stimulus outside moved in the intermediate direction. The monkey was cued to attend to one of the three locations and was required to detect a change in the direction of the cued Gabor. (A) “Normalization Protocol”: The monkey attended outside the receptive field while the preferred and null stimuli were presented at 0%, 50%, or 100% contrasts, thus creating nine stimulus conditions. (B) “Spatial Attention Protocol”: The monkey attended to one of the locations inside the receptive field. (C) Time line of the protocols. See Materials and Methods for details.