N170 – Lancaster Glossary of Child Development

A specific component of the event-related potential (ERP), elicited by upright faces, and observed in adults but not infants, and thus considered to be a neural marker of specialized mechanisms for face processing. In most individuals it is lateralized in the right hemisphere. Meanwhile the component is maximal over occipito-temporal electrode sites, which indicates its source is located in the fusiform and infero-temporal gyri. Compared with responses to visual stimuli other than those of faces, it displays increased negativity some 120-130 ms after stimulus presentation. The first description of N170 was provided by Shlomo Bentin (1945-2012) in 1996 following recording differences in ERP responses to different parts of the face (e.g., eyes) and non-animate objects (e.g., cars). He and his colleagues showed the latency of N170 increased with the presentation of inverted faces (e.g., see the Thatcher effect). There are numerous descriptions available of the technicalities involved in extracting N170 waves. The technique has been used in a number clinically-based studies, For example, in the case of developmental prosopagnosia, there was evidence for normal N170 sensitivity to upright faces, but that the component amplitudes were not enhanced relative to controls. The conclusion drawn is that individuals with developmental propospagnosia do not distinguish between upright and inverted faces, and their face processing system is not selectively attuned to the standard upright orientation. In typical development, N170 does not show the same amplitude enhancement in 3- and 6-month-old infants as adults. The P400 waveform, considered as a potential precursor to the adult N170, revealed only a latency effect to faces, which suggests it does not have this function. P400 was, however, influenced by inversion, with a more negative amplitude being evident for inverted rather than upright faces, but it occurred to both human and monkey faces (revealing a lack of specificity in the processing of faces early in development).