# Familiarity Processing through Faces and Names: Insights from Multivoxel Pattern Analysis
## 4 Discussion  
The sensitivity and flexibility of MVPA for detecting abstract processing permit it to be a valuable approach to complement traditional univariate activation analysis in fMRI studies. In our study, we used a searchlight approach of the MVPA method to determine the way familiarity is represented in the brain. We had two previous hypotheses: (1) one can observe multivoxel patterns for familiarity in different brain areas, reflecting the common properties of the two types of modalities (faces and names), and (2) familiarity can be accurately decoded for a specific modality in some areas, in which no common patterns exist for both kinds of stimuli. The results revealed that whereas certain areas in the brain participate in the processing of familiarity regardless of the type of stimuli, others are specific to the familiarity of faces. Regarding modality-invariant familiarity analysis, the resulting areas were a large set of frontal regions, traditionally activated by the recognition of famous people and the retrieval of biographical semantic information [17; 26; 27]: temporal areas, the left supra-marginal gyrus, the left precuneus, the superior and middle frontal gyrus, and the left middle cingulate gyrus. We did not replicate the previously observed tendency to left lateralization for this set of structures [28], maybe due to the important contribution of faces to the effect of the abstract familiarity in our data. In addition to the modality-invariant familiarity areas, we also found regions that seem to process familiarity specifically for faces. The areas processing face familiarity included bilateral clusters adjacent to the abstract familiarity in the frontal, orbitofrontal, cingulate cortex, precuneus, insula, and supplementary motor area, left temporal pole, left cuneus, left putamen, left pallidum, right inferior temporal and right fusiform gyri. This is consistent  
Figure 4: Clusters of activation resulting from the univariate contrast all faces versus all names. Clusters are shown using an FWE corrected \(p\) < 0.05 (T = 6.007). with other studies that have reported specific areas specialized for face familiarity [17; 27]. Originally, [PERSON] and colleagues' model [1; 2; 3] proposed that the areas of the so-called extended system were not specific for faces, but participated in the processing of socially relevant features associated with them, such as pleasantness and familiarity. Our findings, in line with other MVPA studies, supported the existence of a set of regions that are specific for the processing of those features associated with faces. Those are findings that allow us to suggest that our initial hypotheses are not competitive but indeed complementary. Interestingly, our results also confirmed the growing evidence supporting the involvement of the fusiform gyrus in the processing of face familiarity. The significance of these face-related regions has been underscored by several fMRI studies conducted with prosopagnostic patients [29; 30; 31]. These studies have consistently demonstrated the pivotal role of these regions in face processing. The evidence from imaging studies on this particular issue comes from investigations that use MVPA methods to identify patterns of familiarity information in the brain [32]. The traditional activation-based methods failed to reliably account for subtle differences in the representation of information of similar stimuli with slightly different characteristics, such as familiar and unfamiliar faces [17; 18]. The anterior temporal cortex is another area included in [PERSON]'s model as part of the extended system. It has been associated with the storage of biographical information. Several fMRI studies have reported face-identity discrimination in anterior portions of the temporal lobes, specifically in the area defined as ATL-FA [33; 34; 35]. We did not use an fMRI pulse sequence, specially designed to avoid the susceptibility artifact, which is common in this area, causing signal loss.