Browsing by Subject "facial identity"

Objectives: Faces provide an ideal platform to look into the ways in which our brains process multidimensional information. In order to still recognize an individual when their expression changes, our brain must be able to separate two overlapping sources of information. Previous fMRI-studies have found several brain areas involved in face processing, especially fusiform face area (FFA), occipital face area (OFA), and superior temporal sulcus (STS). EEG- and MEG-studies have also pointed out face-specific temporal components, mainly P1, N170, and N250. However, only few studies have varied both expressions and identities at the same time, or combined spatially precise fMRI with temporally precise M/EEG. Methods: In separate experiments, EEG and fMRI were measured while participants (n=17) viewed morphed faces varying in their expression (neutral, happy, fearful and angry) and in identity. Classification accuracies were calculated using support vector machine (SVM), both from different spatial locations in fMRI and from different timepoints in EEG. In addition, the classification information in fMRI and EEG were combined using representational similarity analysis (RSA). Results: In EEG, we found support for very early processing of expressions (at 110 ms), later processing of identities (at 250 ms) than expressions, and more sustained decoding of angry faces than faces with other expressions. In fMRI, coding of expressions were found on a broad area containing early visual areas and face processing areas OFA, FFA, and STS. Results for identities, although less clear, showed FFA and middle frontal gyrus (MFG). RSA combining both EEG and fMRI showed progression of information from early visual areas at 130 ms to FFA at 150 ms, and to FFA and STS at 200 ms. Conclusions: Our results showed that with multivariate data analysis methods, temporal and spatial neural representations of faces can be studied simultaneously. Consistent with neural models of face processing, our results suggest partially separate processing of expressions and identities in spatially distributed brain network.