Cortical sensitivity to contrast polarity and orientation of faces is modulated by temporal-nasal hemifield asymmetry

Abstract

Behavioral studies demonstrate that the efficiency of detection of faces is dependent on configural and contrast polarity information characteristic to human faces. Stimulus inversion or contrast polarity reversal can disrupt this process. We investigated whether a face-sensitive event-related potential component, the N170, is modulated by the orientation and contrast polarity of highly degraded schematic face-like patterns (Experiment 1) in the same manner as it is for face photographs (Experiment 2). Inversion and/or contrast reversal delayed and enhanced the N170 for both kinds of stimuli, suggesting that a white oval with three black squares is sufficient to elicit face-sensitive cortical responses. In Experiment 3 we further tested whether the extrageniculate visual pathways modulate early cortical responses to faces. We found that the N170 responses to configural and contrast information are modulated by temporal-nasal visual field asymmetry under monocular viewing conditions, suggesting the involvement of subcortical, extrageniculate visual pathways in face detection. These results are consistent with the idea that an ontogenetically early and primitive bias to orient towards face-like patterns with relevant configural and contrast information influences the early stages of cortical face processing.

Steady-state visual-evoked response to upright and inverted geometrical faces: A magnetoencephalography study

“…The topography of the fundamental and harmonic responses was basically distributed over the occipital and temporal areas. Our results revealed no significant difference in the amplitude of SSVEFs between the upright and inverted faces, which is inconsistent with the inversion effect of N170 reported in some previous VEP studies [6][7][8]. A geometrical face-like figure was used as a stimulus in this study, and the lack of reality may have led to the absence of an enlarged response to the inverted stimulus.…”

“…A geometrical face-like figure was used as a stimulus in this study, and the lack of reality may have led to the absence of an enlarged response to the inverted stimulus. However, Tomalski and Jonson [8] presented a simple geometrical face-like figure that was similar to ours, and reported an enlarged N170 with inversion. In addition, previous SSVEP studies that presented face photographs did not find a larger amplitude with face inversion [12,13].…”

“…1, and its inversion (iFace). The face inversion effect on N170 was observed with a simple geometrical face-like figure [8]. Thus, a geometrical figure was presented in this study, to avoid any effect of race, gender, attractiveness, or any other factors that could be found in real photographs.…”

“…First of all, we wanted to avoid the contamination of noise at the alpha range (8)(9)(10)(11)(12) at the fundamental frequency. The projector refresh rate (60 Hz) was also considered because the stimulus was presented as a sinusoidal (rather than abrupt, as in a square wave function; see Fig.…”

“…N170 and its corresponding response on magnetoencephalography (MEG), M170, are known to be affected by face inversion. An inverted face elicits delayed [1,5] or delayed and enhanced [6][7][8] N170, and delayed M170 at least in the right occipito-temporal area [5,9,10]. This effect has been suggested to be face-specific [6], and is referred to as the face inversion effect.…”