The physiological basis of attentional modulation in extrastriate visual areas

Selective attention to color or motion enhances activity in specialized are as of extrastriate cortex, but mechanisms of attentional modulation remain unclear. By dissociating modulation of visually evoked transient activity f rom the baseline for a particular attentional set, human functional neuroim aging was used to investigate the physiological basis of such effects. Base line activity in motion- and color-sensitive areas of extrastriate cortex w as enhanced by selective attention to these attributes, even without moving or colored stimuli. Further, visually evoked responses increased along wit h baseline activity. These results are consistent with the hypothesis that attention modulates sensitivity of neuronal populations to inputs by changi ng background activity.