Abstract
The fMRI adaptation effect refers to a reduced fMRI signal amplitude due to stimulus repetition. In this study, we investigated how attention to different feature dimensions affects face identity fMRI adaptation in the right fusiform face area (FFA). We presented subjects with pairs of faces in an event-related design. The two faces in a pair were presented sequentially and had either the same or different identities, and were moving either in the same or different directions. In Experiment 1, subjects were asked to attend to the second face in a pair and either judge its gender or its direction of motion. In the right FFA, the overall fMRI activation was slightly higher for the gender task than for the motion task. Although the face identity fMRI adaptation was significant in both tasks, it was twice as big in the gender task than it was in the motion task. In Experiment 2, with identical stimulus presentation, subjects were asked to attend to both faces in a pair and judged whether the two faces in a pair had the same or different identities or had the same or different directions of motion. The overall fMRI activation in the right FFA was significantly higher for the face same/different task than it was for the motion same/different task. The face identity fMRI adaptation was again significant in both tasks, however this time, the amount adaptation was comparable between the two tasks. These results indicate that when attention was directed to one of the two stimuli in a pair, identity adaptation is modulated by the feature dimension attended to; when attention was directed to both stimuli in a pair, identity adaptation is comparable regardless of the feature dimension attended to.