This study investigates the electrophysiological responses associated with face perception in humans. Event-related potentials (ERPs) were recorded from normal volunteers while they performed a visual target detection task. The stimuli included human faces, animal faces, cars, and other non-face items. The results showed that human faces elicited a negative potential at 172 msec (N170), which was absent from ERPs elicited by other non-face stimuli. N170 was largest over the posterior temporal scalp and was larger over the right hemisphere than the left. N170 was delayed when faces were presented upside-down, but its amplitude did not change. When presented in isolation, eyes elicited a larger N170 than whole faces, while noses and lips elicited smaller negative ERPs. Distorted human faces elicited an N170 similar in amplitude to that elicited by normal faces. However, faces of animals, human hands, cars, and furniture did not evoke N170. These findings suggest that N170 reflects a neural mechanism tuned to detect human faces, similar to the "structural encoder" proposed by Bruce and Young (1986). The differential sensitivity of N170 to eyes in isolation suggests that N170 may reflect the activation of an eye-sensitive region of cortex. The voltage distribution of N170 over the scalp is consistent with a neural generator located in the occipitotemporal sulcus lateral to the fusiform/inferior temporal region that generates N200. The study also examined the effects of face inversion, distortion, and isolation on N170. Inverted faces elicited a delayed N170, but its amplitude was not significantly different from upright faces. Distorted faces elicited a similar N170 to normal faces, suggesting that N170 is not dependent on the spatial integrity of facial components. Isolated eyes elicited a larger N170 than whole faces, indicating that N170 may reflect the processing of eye-specific information. The results suggest that N170 is not related to face recognition per se, but to the detection of facial features. The study also found that N170 was not elicited by animal faces, cars, or other non-face stimuli, further supporting the idea that N170 reflects a neural mechanism tuned to detect human faces. The findings have implications for understanding the neural mechanisms underlying face perception and recognition.This study investigates the electrophysiological responses associated with face perception in humans. Event-related potentials (ERPs) were recorded from normal volunteers while they performed a visual target detection task. The stimuli included human faces, animal faces, cars, and other non-face items. The results showed that human faces elicited a negative potential at 172 msec (N170), which was absent from ERPs elicited by other non-face stimuli. N170 was largest over the posterior temporal scalp and was larger over the right hemisphere than the left. N170 was delayed when faces were presented upside-down, but its amplitude did not change. When presented in isolation, eyes elicited a larger N170 than whole faces, while noses and lips elicited smaller negative ERPs. Distorted human faces elicited an N170 similar in amplitude to that elicited by normal faces. However, faces of animals, human hands, cars, and furniture did not evoke N170. These findings suggest that N170 reflects a neural mechanism tuned to detect human faces, similar to the "structural encoder" proposed by Bruce and Young (1986). The differential sensitivity of N170 to eyes in isolation suggests that N170 may reflect the activation of an eye-sensitive region of cortex. The voltage distribution of N170 over the scalp is consistent with a neural generator located in the occipitotemporal sulcus lateral to the fusiform/inferior temporal region that generates N200. The study also examined the effects of face inversion, distortion, and isolation on N170. Inverted faces elicited a delayed N170, but its amplitude was not significantly different from upright faces. Distorted faces elicited a similar N170 to normal faces, suggesting that N170 is not dependent on the spatial integrity of facial components. Isolated eyes elicited a larger N170 than whole faces, indicating that N170 may reflect the processing of eye-specific information. The results suggest that N170 is not related to face recognition per se, but to the detection of facial features. The study also found that N170 was not elicited by animal faces, cars, or other non-face stimuli, further supporting the idea that N170 reflects a neural mechanism tuned to detect human faces. The findings have implications for understanding the neural mechanisms underlying face perception and recognition.