John Maunsell
Department of Neurobiology, Harvard Medical School
Several studies have examined how attention affects the tuning response functions of individual neurons in monkey visual cortex. Two distinct effects have been described. Some experiments have reported that attention acts like a change in sensitivity, so that responses to all stimuli increase by the same proportion (response gain). Other experiments that have examined responses to stimuli of different contrasts have reported that attention has proportionally more effect on responses to stimuli of low contrast (contrast gain). We have examined this distinction in more detail in recordings from neurons in monkey V4 and MT. The results suggest that the effects of attention on the responses of most neurons can be well described by either model, however data with the greatest resolution are more consistent with a proportional modulation of responses to all stimuli.