Electrophysiological evidence for separation between human face and non-face object processing only in the right hemisphere

Sexual Dimorphism in Hemispheric Processing of Faces in Humans: A Meta-Analysis of 817 Cases

A well-established neuroimaging literature predicts a right-sided asymmetry in the activation of face-devoted areas such as the fusiform gyrus (FG) and its resulting M/N170 response during face processing. However, the face-related response sometimes appears to be bihemispheric. A few studies have argued that bilaterality depended on the sex composition of the sample. To shed light on this matter, two meta-analyses were conducted starting from a large initial database of 250 ERP (Event-related potentials)/MEG (Magnetoencephalography) peer-reviewed scientific articles. Paper coverage was from 1985 to 2020. Thirty-four articles met the inclusion criteria of a sufficiently large and balanced sample size with strictly right-handed and healthy participants aged 18–35 years and N170 measurements in response to neutral front view faces at left and right occipito/temporal sites. The data of 817 male (n = 414) and female (n = 403) healthy adults were subjected to repeated-measures analyses of variance. The results of statistical analyses from the data of 17 independent studies (from Asia, Europe and America) seem to robustly indicate the presence of a sex difference in the way the two cerebral hemispheres process facial information in humans, with a marked right-sided asymmetry of the bioelectrical activity in males and a bilateral or left-sided activity in females.

Frontoparietal microstructural damage mediates age-dependent working memory decline in face and body information processing: Evidence for dichotomic hemispheric bias mechanisms

Age-associated damage in the microstructure of frontally-based connections (e.g. genu of the corpus callosum and superior longitudinal fasciculus) is believed to lead to impairments in processing speed and executive function. Using mediation analysis, we tested the potential contribution of callosal and frontoparietal association tracts to age-dependent effects on cognition/executive function as measured with 1-back working memory tasks for visual stimulus categories (i.e. faces and non-emotional bodies) in a group of 55 healthy adults (age range 23-79 years). Constrained spherical deconvolution-based tractography was employed to reconstruct the genu/prefrontal section of the corpus callosum (GCC) and the central/second branch of the superior longitudinal fasciculus (CB-SLF). Age was associated with (i) reductions in fractional anisotropy (FA) in the GCC and in the right and left CB-SLF and (iii) decline in visual object category processing. Mediation analysis revealed that microstructural damage in right hemispheric CB-SLF is associated with age-dependent decline in face processing likely reflecting the stimulus-specific/holistic nature of face processing within dedicated/specialized frontoparietal routes. By contrast, microstructural damage in left hemispheric CB-SLF associated with age-dependent decline in non-emotional body processing, consistent with the more abstract nature of non-emotional body categories. In sum, our findings suggest that frontoparietal microstructural damage mediates age-dependent decline in face and body information processing in a manner that reflects the hemispheric bias of holistic vs. abstract nature of face and non-emotional body category processing.

Mental rotation of alphabet characters affects the face-sensitive N170 component

Face-sensitive N170 component of event-related potential is sensitive to face inversion, which has been defined as the face-inversion effect. Moreover, a previous study suggested that similar to the face-inversion effect of the face-sensitive N170 affected by mental rotation of the face, object-related N170 of three-dimensional objects was also affected by the mental rotation of two-dimensional objects. The purpose of the present study was to compare the relationship between face-sensitive N170 during face perception (upright and inverted faces) and object-related N170 during character perception (normal and mirror version for alphabet characters). The results indicated that the latency of N170 for mirror version for alphabet characters was significantly longer than that for normal version for alphabet characters, and the latency of N170 for inverted faces was significantly longer than that for upright faces. Therefore, the results of the present study clearly indicate that face-sensitive N170 components are related to the mental rotation of normal and mirror version for alphabet characters. These results suggest the novel possibility that face-sensitive N170 latency can be used as a biomarker for mental rotation and that mental rotation is related to the fusiform area as a neural generator of N170 in the human brain.

Face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects

Studies investigating event-related potentials have reported on face-sensitive P1 and N170 components, as well as object-related N170 components. Face-sensitive N170 is also sensitive to face inversion, which has been defined as the face-inversion effect. This study aimed to directly compare the relationship between face-sensitive N170 during face perception (upright and inverted faces) and object-related N170 during object perception (two-dimensional and three-dimensional objects). More specifically, the purpose was to clarify whether face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects. Electroencephalography was performed in participants who were shown one of the four types of stimuli: upright faces, inverted faces, two-dimensional objects, or three-dimensional objects. The results revealed that the latency of P1 for three-dimensional objects was significantly longer than that for two-dimensional objects, the latency of N170 for three-dimensional objects was significantly longer than that for two-dimensional objects, and the latency of N170 for inverted faces was significantly longer than that for upright faces. These findings suggest that face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects. Moreover, the results suggest that, similar to the face-inversion effect of face-sensitive N170 affected by mental rotation of the face, the object-related N170 of three-dimensional objects was affected by the mental rotation of two-dimensional objects. This suggests the novel possibility that face-sensitive P1 and N170 components can be used as an index for the perception of two-dimensional and three-dimensional objects.