Selective attention enhances neuronal responsiveness to attended sensory stimuli.
In this experiment, the results of which are presented in the next slide, the animal is required to fixate on the small circle in the center of the screen. The receptive field of the recorded cortical neuron is noted (dashed box). A white cue box tells the animal where to fixate his attention. The responsiveness of the cell is then tested with stimuli of varying levels of contrast and sorted according to whether or not the animal was attending to the region of the receptive field of the neuron or not. Note that the animal is required to maintain fixation on the center fixation point at all times during each trial - the eyes dont move, only the region of attention does. (Target stimuli are to test that the animal is attending to the correct location and are to be followed by moving a lever.)
From Reynolds, Pasternak, and Desimone (2000) Attention increases sensitivity of V4 neurons. Neuron 26: 703-714.