S19-1. A face recognition study with morphing human face into monkey face

Abstract

In general, N170 in response to human face is larger in amplitude than other face categories, and N170 shows larger amplitude for the inverted face than for the upright face (face inversion effect, FIE). However, it is still controversial that the differences in N170 among the face categories are due to physical variances such as contrast and spatial frequency (SF). In order to elucidate the face- and species-specificity of N170, high-density ERPs were recorded in 10 adults while viewing morphing faces between human and monkey. We used two types of stimuli with controlled SF and uncontrolled one. When viewing the controlled SF stimuli, both amplitudes and latencies of N170 were significantly modulated in proportion to the human ratio. Moreover, the larger amplitudes of FIE were observed only for faces which contained higher human ratio though the latencies were delayed in all faces. In contrast, N170 showed no differences among the stimuli using the uncontrolled SF stimuli. However, FIE showed similar trends observed under the controlled SF stimuli in both latencies and amplitudes. These findings suggest the importance of SF and human ratio on N170. Therefore, we conclude that N170 reflects species-specific face processing and that FIE is influenced by species.