A distributed neural system for top-down face processing

Abstract

Evidence suggests that the neural system associated with face processing is a distributed cortical network containing both bottom-up and top-down mechanisms. While bottom-up face processing has been the focus of many studies, the neural areas involved in the top-down face processing have not been extensively investigated due to difficulty in isolating top-down influences from the bottom-up response engendered by presentation of a face. In the present study, we used a novel experimental method to induce illusory face-detection. This method allowed for directly examining the neural systems involved in top-down face processing while minimizing the influence of bottom-up perceptual input. A distributed cortical network of top-down face processing was identified by analyzing the functional connectivity patterns of the right fusiform face area (FFA). This distributed cortical network model for face processing includes both "core" and "extended" face processing areas. It also includes left anterior cingulate cortex (ACC), bilateral orbitofrontal cortex (OFC), left dorsolateral prefrontal cortex (DLPFC), left premotor cortex, and left inferior parietal cortex. These findings suggest that top-down face processing contains not only regions for analyzing the visual appearance of faces, but also those involved in processing low spatial frequency (LSF) information, decision-making, and working memory.

Fig. 1

The sequence of displays in a trial (left to right) and examples of the four types of stimuli used in the experiment (A to D). During training, the first phase used image 50% noise image stimuli (A) for face present trials. The second phase used 75% noise image stimuli (B) for face present trials. Finally, by the end of training, all trials were pure noise (C), although participants were instructed that half of the trials still contained faces. Checkerboard images were used as controls (D).

Fig. 2

The PPI analysis map. Areas illustrated in this map show a greater covariation with the right FFA activity for illusory face response trials compared to non-face response trials. The threshold was set at T > 3.11 (P < 0.005, uncorrected) and minimum cluster volume = 15 voxels. The color bar represents T values. The numbers beneath each image refer to the z coordinates of Talairach. A, bilateral Fusiform Gyrus; B, bilateral amygdala; C, right hippocampus; D, bilateral Orbitofrontal Cortex; E, left Superior Temporal Sulcus; F, left Anterior Cingulate Cortex; G, left Inferior Frontal Gyrus; H, left Dorsolateral Prefrontal Cortex; I, left Superior Frontal Gyrus; J, left Inferior Parietal Lobule; K, left Premotor Cortex; L, left; R, right;