Does face-selective cortex show a left visual field bias for centrally-viewed faces?

Altered face perception in amnestic mild cognitive impairment: Evidence from representational similarity analysis of event-related potential

BackgroundStructural changes in medial temporal lobes including the fusiform gyrus, a critical area in face recognition, precede the progression of amnestic mild cognitive impairment (aMCI) to Alzheimer's disease (AD). However, how the neural correlates of face processing altered in aMCI, as well as their association with cognitive impairments, remain unclear.ObjectiveUsing electroencephalogram (EEG), we explored the electrophysiological markers of face-specific visual processing alterations in aMCI and examined their relationship with cognitive deficits.MethodsWe recruited participants with aMCI (n = 32) and healthy controls (HC, n = 41) and used a passive viewing task to measure the event-related potential (ERP) in response to faces and non-face objects. To compare face processing in aMCI patients and HCs, we adopted mass univariate analysis and representational similarity analysis (RSA) to explore aMCI-related alterations in ERPs.ResultsWe found that face inversion effect (FIE) in P1 amplitudes was absent in aMCI patients. Also, compared to HCs, aMCI patients exhibited a lack of right hemisphere advantage in N170 in response to faces. Furthermore, representation similarity analysis of ERP in posterior-temporal regions revealed that aMCI patients represent face and non-face objects distinctively from HCs in the early processing stage. Additionally, the FIE in P1 amplitude positively correlated to aMCI patients' visuospatial functions.ConclusionsThese findings showed aMCI-related changes in the early perceptual processing of faces and highlights the potential of the FIE in P1 amplitude and ERP patterns over occipital-temporal regions as electrophysiological markers for aMCI and AD.

Disorders of Higher-order Visual Function

OBJECTIVE

This article provides an overview of disorders of higher-order visual function, encompassing key clinical features, methods for clinical assessment, anatomic localization, and etiologies associated with these disorders. A review of the organization and properties of the brain's visual system is introduced to enhance understanding and facilitate clinical recognition of higher-order visual dysfunction.

LATEST DEVELOPMENTS

Advances in the visual neurosciences have increased our understanding of the underlying properties of visual neurons. New therapies are available to treat diseases that impact cortical neurons and their white matter connections. Thus, recognizing the signs and symptoms of these disorders and using the proper assessment tools to measure dysfunction are essential for preventing disability.

ESSENTIAL POINTS

Functional specialization for distinct visual features defines higher-order visual regions and their corresponding networks. Damage to specialized regions along the occipitoparietal pathway leads to impaired motion processing and visuospatial perception, whereas damage to the occipitotemporal regions results in visual agnosia, including impaired color, object, and facial recognition. Patients experiencing higher-order visual dysfunction do not express symptoms significantly different from those with ocular disorders. Identifying higher-order visual dysfunction requires knowledge of the anatomy and visual properties of neurons in these regions. Assessment of higher-order visual functions can be incorporated into the neurologic mental status examination and prevent delays in diagnosis.

A framework for analyzing EEG data using high-dimensional tests

MOTIVATION

The objective of EEG data analysis is to extract meaningful insights, enhancing our understanding of brain function. However, the high dimensionality and temporal dependency of EEG data present significant challenges to the effective application of statistical methods. This study systematically addresses these challenges by introducing a high-dimensional statistical framework that includes testing changes in the mean vector and precision matrix, as well as conducting relevant analyses. Specifically, the Ridgelized Hotelling's T2 test (RIHT) is introduced to test changes in the mean vector of EEG data over time while relaxing traditional distributional and moment assumptions. Secondly, a multiple population de-biased estimation and testing method (MPDe) is developed to estimate and simultaneously test differences in the precision matrix before and after stimulation. This approach extends the joint Gaussian graphical model to multiple populations while incorporating the temporal dependency of EEG data. Meanwhile, a novel data-driven fine-tuning method is applied to automatically search for optimal hyperparameters.

RESULTS

Through comprehensive simulation studies and applications, we have obtained substantial evidence to validate that the RIHT has relatively high power, and it can test for changes when the distribution is unknown. Similarly, the MPDe can infer the precision matrix under time-dependent conditions. Additionally, the conducted analysis of channel selection and dominant channel can identify significant channels which play a crucial role in human cognitive ability, such as PO3, PO4, Pz, P4, P8, FT7, and FT8. All findings confirm that the proposed methods outperform existing ones, demonstrating the effectiveness of the framework in EEG data analysis.

AVAILABILITY AND IMPLEMENTATION

Source code and data used in the article are available at https://github.com/yahu911/Framework_EEG.

Genetic and environmental contributions to gaze lateralization across social and non-social stimuli in human infants

A tendency to look at the left side of faces from the observer's point of view has been found in older children and adults, but it is not known when this face-specific left gaze bias develops and what factors may influence individual differences in gaze lateralization. Therefore, the aims of this study were to estimate gaze lateralization during face observation and to more broadly estimate lateralization tendencies across a wider set of social and non-social stimuli, in early infancy. In addition, we aimed to estimate the influence of genetic and environmental factors on lateralization of gaze. We studied gaze lateralization in 592 5-month-old twins (282 females, 330 monozygotic twins) by recording their gaze while viewing faces and two other types of stimuli that consisted of either collections of dots (non-social stimuli) or faces interspersed with objects (mixed stimuli). A right gaze bias was found when viewing faces, and this measure was moderately heritable (A = 0.38, 95% CI 0.24; 0.50). A left gaze bias was observed in the non-social condition, while a right gaze bias was found in the mixed condition, suggesting that there is no general left gaze bias at this age. Genetic influence on individual differences in gaze lateralization was only found for the tendency to look at the right versus left side of faces, suggesting genetic specificity of lateralized gaze when viewing faces.

Self-reported eye contact sensitivity and face processing in chromosome 22q11.2 deletion syndrome

INTRODUCTION

22q11.2 deletion syndrome (22qDS) has been associated with varying levels of social impairments, and with atypical visual scanning of faces. The present study explored whether self-reported sensitivity to eye contact might be related to these phenomena.

METHOD

Individuals with confirmed 22qDS were interviewed about their experience and possible discomfort with eye contact. In cases where individuals expresesed discomfort, they were subsequently asked about coping mechanisms used to deal with this discomfort. In addition to self-reported eye contact discomfort, gaze to emotional faces was examined using eye tracking.

RESULTS

In the subgroup of individuals who reported discomfort during eye contact, eye tracking results revealed a lower amount of gaze in the eyes of neutral faces, as well as the absence of the typical left visual field (LVF) bias, indicative of alterations in hemispheric lateralization. This subgroup also scored lower on a measure of everyday functioning.

CONCLUSIONS

Our results show that, by simply asking individuals with this social and communicative disorder about eye gaze discomfort, we may better understand the specific challenges that they experience. Moreover, information gained from such first-person reports together with eye-tracking measures further informs about the integrity of their face processing system, as well as about the nature and degree of impairment in this population.

The Left-Side Bias Is Reduced to Other-Race Faces in Caucasian Individuals

One stable marker of face perception appears to be left-side bias, the tendency to rely more on information conveyed by the left side of the face than the right. Previous studies have shown that left-side bias is influenced by familiarity and prior experience with face stimuli. Since other-race facial recognition is characterized by reduced familiarity, in contrast to own-race facial recognition, the phenomenon of left-side bias is expected to be weaker for other-race faces. Among Chinese participants, face inversion has been found to eliminate the left-side bias associated with own-race faces. Therefore, it is of interest to know whether face inversion influences left-side bias for non-Chinese research participants and can be generalized across own- and other-race faces. This study assessed 65 Caucasian participants using upright and inverted chimeric Caucasian and Asian faces in an identity similarity-judgment task. Although a significant left-side bias was observed for upright own-race faces, this bias was eliminated by facial inversion, indicating that such a bias depends on the applicability of configural processing strategies. For other-race faces, there was no left-side bias in the upright condition. Interestingly, the inverted presentation yielded a right-side bias. These results show that while left-side bias is affected by familiarity differences between own- and other-race faces, it is a universal phenomenon for upright faces. Inverted presentation strongly reduces left-side bias and may even cause it to revert to right-side bias, suggesting that left-side bias depends on configural face processing.