Perceived animacy influences the processing of human-like surface features in the fusiform gyrus

Abstract

While decades of research have demonstrated that a region of the right fusiform gyrus (FG) responds selectively to faces, a second line of research suggests that the FG responds to a range of animacy cues, including biological motion and goal-directed actions, even in the absence of faces or other human-like surface features. These findings raise the question of whether the FG is indeed sensitive to faces or to the more abstract category of animate agents. The current study uses fMRI to examine whether the FG responds to all faces in a category-specific way or whether the FG is especially sensitive to the faces of animate agents. Animate agents are defined here as intentional agents with the capacity for rational goal-directed actions. Specifically, we examine how the FG responds to an entity that looks like an animate agent but that lacks the capacity for goal-directed rational action. Region-of-interest analyses reveal that the FG activates more strongly to the animate compared with the inanimate entity, even though the surface features of both animate and inanimate entities were identical. These results suggest that the FG does not respond to all faces in a category-specific way, and is instead especially sensitive to whether an entity is animate.

Keywords: Animacy detection; Face processing; Fusiform; Goal-directed actions; Posterior superior temporal sulcus; fMRI.

Figure 1. Example still frames from movie clips

(A) The rational character (on left) walked towards the wall, turned towards the opening, and continued walking. The irrational character (on right) repeatedly walked into the wall without adjusting his motion trajectory. (B) The rational character (on left) walked towards the box, bent down, and picked it up. The irrational character (on right) walked to the left of the box, bent down, and performed a lifting motion as though they were lifting the box. The identity of the rational and irrational characters was counterbalanced across participants.

Figure 2. Activation map for the Rational versus Irrational contrast

Activation is displayed on a cortical surface representation. The color ranges from z = 2.3 to z = 5.0.

Figure 3. Activation map for the Irrational versus Rational contrast

Activation is displayed on a cortical surface representation. The color ranges from z = 2.3 to z = 4.1.

Figure 4. ROI analysis results for the FG: percent signal change during movie clips

Percent signal change averaged across voxels in the independently identified FG ROI (pictured in top right) for the rational (blue) and irrational (red) conditions. There is a significant difference in the peak percent signal change in response to the rational (animate) compared with the irrational (inanimate) condition. Movie presentation begins at 0s.

Figure 5. ROI analysis results for the FG: percent signal change during static presentation of faces shown after the movie clips

Percent signal change averaged across voxels in the independently identified FG ROI (pictured in top right) for the rational (blue) and irrational (red) conditions. There is a significant difference in the peak percent signal change in response to the rational (animate) compared with the irrational (inanimate) condition. Stimulus presentation begins at 0s.