Internal and external features of the face are represented holistically in face-selective regions of visual cortex

Abstract

The perception and recognition of familiar faces depends critically on an analysis of the internal features of the face (eyes, nose, mouth). We therefore contrasted how information about the internal and external (hair, chin, face outline) features of familiar and unfamiliar faces is represented in face-selective regions. There was a significant response to both the internal and external features of the face when presented in isolation. However, the response to the internal features was greater than the response to the external features. There was significant adaptation to repeated images of either the internal or external features of the face in the fusiform face area (FFA). However, the magnitude of this adaptation was greater for the internal features of familiar faces. Next, we asked whether the internal features of the face are represented independently from the external features. There was a release from adaptation in the FFA to composite images in which the internal features were varied but the external features were unchanged, or when the internal features were unchanged but the external features varied, demonstrating a holistic response. Finally, we asked whether the holistic response to faces could be influenced by the context in which the face was presented. We found that adaptation was still evident to composite images in which the face was unchanged but body features were varied. Together, these findings show that although internal features are important in the neural representation of familiar faces, the face's internal and external features are represented holistically in face-selective regions of the human brain.

Figure 1.

Localizer scan. Top, Location of face-selective regions (FFA, OFA, STS) across all subjects in a whole-brain group analysis. These scan images follow radiological convention, with the left hemisphere shown on the right. Bottom, MR time course during localizer scans, showing activity averaged across hemispheres and subjects for each stimulus category in face-selective areas. The shaded regions represent the duration of each stimulus block. Error bars represent ±SE.

Figure 2.

Experiment 1—adaptation to internal and external features of familiar faces. Left, Examples of familiar faces. Right, The average time course of response across subjects in the FFA, the OFA, and the STS. The shaded regions represent the duration of stimulus presentation. Error bars represent ±SE.

Figure 3.

Experiment 1—adaptation to internal and external features of unfamiliar faces. Left, Examples of unfamiliar faces. Right, The average time course of response across subjects in the FFA, the OFA, and the STS. The shaded regions represent the duration of stimulus presentation. Error bars represent ±SE.

Figure 4.

Experiment 1—adaptation to internal and external features of faces. The average adaptation response in the FFA to internal and external features of familiar and unfamiliar faces in experiment 1. There was a significant interaction between feature and identity for familiar faces, which was explained by a larger adaptation effect (diff. − same) for internal than for external features of the face. A similar difference was not evident for unfamiliar faces.

Figure 5.

Experiment 2—Adaptation to composite (internal/external) images of familiar faces. Top, Example of images from different conditions (row 1: same internal, same external; row 2: same internal, different external; row 3: different internal, same external; row 4: different internal, different external). Bottom, The average time course of response across subjects in face-selective regions. Error bars represent ±SE.

Figure 6.

Experiment 2—adaptation to composite (internal/external) images of unfamiliar faces. Top, Example of images from different conditions (row 1: same internal, same external; row 2: same internal, different external; row 3: different internal, same external; row 4: different internal, diff. external). Bottom, The average time course of response across subjects in face-selective regions. Error bars represent ±SE.

Figure 7.

Experiment 3—the role of context in face processing. Top, Example of composite images (row 1: same face, same bust; row 2: same face, diff. bust; row 3: diff. face, same bust; row 4: diff. face, diff. bust). Bottom, The average time course of response across subjects in the core face-selective regions. Error bars represent ±SE.