TASK-DEPENDENT INFLUENCES OF ATTENTION ON THE ACTIVATION OF HUMAN PRIMARY VISUAL-CORTEX

There has been a good deal of controversy over whether attention influ ences area V1-the first cortical area onto which information from the retina is projected, Attention to motion has been found to modulate mo nkey area MT and the human homolog of MT/MST. Here we show that activa tion of V1 by attention to motion is task dependent. Our stimulus cons isted of a group of translating random dots superimposed over another group of random dots executing expansion motion. Subjects were instruc ted to pay attention selectively to the translation, expansion, or nei ther in particular (passive condition). The activity in the human MT/M ST homolog measured by functional magnetic resonance imaging (fMRI) wa s significantly higher in both the translation and the expansion condi tions than in the passive condition, while the activity in area V1 was significantly higher only in the translation condition. These results show that attention to motion modulates area VI, and more interesting ly that high-level cognitive processing such as attention may directly or indirectly determine the retroactive extent of feedback within the motion pathway in a manner dependent on the type of motion attended.