Distinct but Overlapping Patterns of Response to Words and Faces in the Fusiform Gyrus

Abstract

Converging evidence suggests that the fusiform gyrus is involved in the processing of both faces and words. We used fMRI to investigate the extent to which the representation of words and faces in this region of the brain is based on a common neural representation. In Experiment 1, a univariate analysis revealed regions in the fusiform gyrus that were only selective for faces and other regions that were only selective for words. However, we also found regions that showed both word-selective and face-selective responses, particularly in the left hemisphere. We then used a multivariate analysis to measure the pattern of response to faces and words. Despite the overlap in regional responses, we found distinct patterns of response to both faces and words in the left and right fusiform gyrus. In Experiment 2, fMR adaptation was used to determine whether information about familiar faces and names is integrated in the fusiform gyrus. Distinct regions of the fusiform gyrus showed adaptation to either familiar faces or familiar names. However, there was no adaptation to sequences of faces and names with the same identity. Taken together, these results provide evidence for distinct, but overlapping, neural representations for words and faces in the fusiform gyrus.

Keywords: FFA; VWFA; face; name; word.

Figure 1.

Examples of the stimuli from each of the experimental conditions in Experiment 1.

Figure 2.

Examples of stimuli from the experimental conditions in Experiment 2: (a) Same-face and different-face conditions, (b) same-name and different-name conditions, and (c) same identity, face + name, and different identity face + name.

Figure 3.

Fusiform gyrus mask. The analysis was restricted to a bilateral fusiform mask generated by combining the following masks from the Harvard Oxford Atlas in the MNI space: (1) Occipital fusiform (red), (2) occipital temporal fusiform (green), (3) posterior fusiform (blue), and (4) anterior fusiform (yellow). This mask was back-transformed into each participants EPI space for analyses which were performed in the individual's EPI space.

Figure 4.

Face-selective and word-selective voxels in the fusiform gyrus. (a) Voxels within the fusiform gyrus that responded selectively to faces are shown in red. (b) Voxels within the fusiform gyrus that responded selectively to words are shown in (blue). (c) Percentage of voxels within the fusiform gyrus that responded selectively to faces (red), selectively to words (blue), and both to faces and words (green). This shows predominantly overlapping responses to faces and words in the left fusiform gyrus. However, in the right fusiform gyrus, the response is predominately to faces. Statistical images were thresholded at Z > 2.3.

Figure 5.

MVPA showing the within-category and between-category correlations for the patterns of response to words and faces in the fusiform gyrus mask. Correlations were based on the data from odd and even blocks. There were distinct patterns of response to both faces and words in both the right and the left fusiform gyrus.

Figure 6.

Adaptation to faces and words in the fusiform gyrus. (a) Voxels within the fusiform gyrus showing adaptation to familiar faces are shown in red. (b) Voxels within the fusiform gyrus showing adaptation to familiar names are shown in blue. (c) Voxels within the fusiform gyrus showing adaptation to familiar faces + names are shown in green. (d) Percentage of voxels within the fusiform gyrus that showed adaptation to faces (red), adaptation to names (blue), and faces + names (green). There was bilateral adaptation to both faces and names; however, we found no significant adaptation to blocks of faces + names. Statistical images were thresholded at Z > 2.3.