Slide 4

Spatial Attention Results in an Enhancement of V4 Neurons to Low Contrast Visual Stimuli

Firing rate of a V4 neuron during trials in which the animal was instructed to pay attention to the region of the receptive field of the recorded cell (solid black line) or away from the receptive field (gray line). Subtracting the Non-attend response curve from the attend curve results yields the illustrated different curve (dotted line). The percent increase in response with attention is illustrated with the dashed line. 

This result demonstrates that attention can enhance the response or V4 neurons to low contrast (e.g. weak) visual stimuli. Responses to high contrast stimuli are relatively un-affected. This results in a shift of the input-output curve to the left and an apparent increase in its slope.

From Reynolds, Pasternak, and Desimone (2000) Attention increases sensitivity of V4 neurons. Neuron 26: 703-714.