Attention

Effects of Attention on Neuronal Contrast response Functions

Although it is well established that attention makes neuronal responses stronger, few studies have examined whether attention changes the selectivity of neurons. Those studies are largely consistent in showing that attention makes responses stronger without appreciably changing the width of tuning for stimulus dimensions such as orientation or direction. These results suggest that the effects of attention can be explained by a gain change, which increases a neuron's response to all stimuli proportionally. However, other experiments suggest that attention increases responses to low-contrast stimuli far more than it increases responses to high-contrast stimuli, a property that cannot be explained by a simple gain change. We have examined these different accounts of the action of attention by examining the interactions between orientation, contrast and spatial attention in determining the responses of individual neurons in area V4 of monkey visual cortex.

Our results suggest that the effects of attention on contrast response functions are well explained by simple changes in gain, just like those that explain effects on stimulus dimensions like orientation or contrast.

We believe that the differing conclusions arise from the fact that the effects of attention on contrast response functions are well explained by either changes in sensitivity or by a mechanism that act preferentially at intermediate and low contrasts. The earlier reports favored the latter interpretation, but did not rule out the simpler mechanism of an increase in sensitivity