N170

The N170 is a component of the event-related potential (ERP) that reflects the neural processing of faces, familiar objects or words. Furthermore, the N170 is modulated by prediction error processes. When potentials evoked by images of faces are compared to those elicited by other visual stimuli, the former show increased negativity 130-200 ms after stimulus presentation. This response is maximal over occipito-temporal electrode sites, which is consistent with a source located at the fusiform and inferior-temporal gyri, confirmed by electrocorticography. The N170 generally displays right-hemisphere lateralization and has been linked with the structural encoding of faces, hence is considered to be primarily sensitive to faces. A study, employing transcranial magnetic stimulation combined with EEG, found that N170 can be modulated by top-down influences from prefrontal cortex. The N170 was first described by Shlomo Bentin and colleagues in 1996, who measured ERPs from participants viewing faces and other objects. They found that human faces and face parts (such as eyes) elicited different responses than other stimuli, including animal faces, body parts, and cars. Earlier work performed by Botzel and Grusser and first reported in 1989 also attempted to find a component of the ERP that corresponded to the processing of human faces. They showed observers line drawings (in one experiment) and black-and-white photographs (in two additional experiments) of faces, trees, and chairs. They found that, compared to the other stimulus classes, faces elicited a larger positive component approximately 150 ms after onset, which was maximal at central electrode sites (at the top of the head). The topography of this effect and lack of lateralization led to the conclusion that this face-specific potential did not arise in face-selective areas in the occipital-temporal region, but instead in the limbic system. Subsequent work referred to this component as the vertex positive potential (VPP).