How does the brain process upright and inverted faces?

The face inversion effect (FIE) is defined as the larger decrease in recognition performance for faces than for other mono-oriented objects when they are presented upside down. Behavioral studies suggest the FIE takes place at the perceptual encoding stage and is mainly due to the decrease in ability to extract relational information when discriminating individual faces. Recently, functional magnetic resonance imaging and scalp event-related potentials studies found that turning faces upside down slightly but significantly decreases the response of face-selective brain regions, including the so-called fusiform face area (FFA), and increases activity of other areas selective for nonface objects. Face inversion leads to a significantly delayed (sometimes larger) N170 component, an occipito-temporal scalp potential associated with the perceptual encoding of faces and objects. These modulations are in agreement with the perceptual locus of the FIE and reinforce the view that the FFA and N170 are sensitive to individual face discrimination.