Exploring the Role of Spatial Frequency Information during Neural Emotion Processing in Human Infants

Signatures of emotional face processing measured by event-related potentials in 7-month-old infants

The ability to distinguish facial emotions emerges in infancy. Although this ability has been shown to emerge between 5 and 7 months of age, the literature is less clear regarding the extent to which neural correlates of perception and attention play a role in processing of specific emotions. This study's main goal was to examine this question among infants. To this end, we presented angry, fearful, and happy faces to 7-month-old infants (N = 107, 51% female) while recording event-related brain potentials. The perceptual N290 component showed a heightened response for fearful and happy relative to angry faces. Attentional processing, indexed by the P400, showed some evidence of a heightened response for fearful relative to happy and angry faces. We did not observe robust differences by emotion in the negative central (Nc) component, although trends were consistent with previous work suggesting a heightened response to negatively valenced expressions. Results suggest that perceptual (N290) and attentional (P400) processing is sensitive to emotions in faces, but these processes do not provide evidence for a fear-specific bias across components.

Early antecedents of emotion differentiation and regulation: Experience tunes the appraisal thresholds of emotional development in infancy

In this review, we synthesize evidence to highlight cognitive appraisal as an important developmental antecedent of individual differences in emotion differentiation and adept emotion regulation. Emotion differentiation is the degree to which emotions are experienced in a nuanced or "granular" way-as specific and separable phenomena. More extensive differentiation is related to positive wellbeing and has emerged as a correlate of emotion regulation skill among adults. We argue that the cognitive appraisal processes that underlie these facets of emotional development are instantiated early in the first year of life and tuned by environmental input and experience. Powerful socializing input in the form of caregivers' contingent and selective responding to infants' emotional signals carves and calibrates the infant's appraisal thresholds for what in their world ought to be noticed, deemed as important or personally meaningful, and responded to (whether and how). These appraisal thresholds are thus unique to the individual child despite the ubiquity of the appraisal process in emotional responding. This appraisal infrastructure, while plastic and continually informed by experience across the lifespan, likely tunes subsequent emotion differentiation, with implications for children's emotion regulatory choices and skills. We end with recommendations for future research in this area, including the urgent need for developmental emotion science to investigate the diverse sociocultural contexts in which children's cognitive appraisals, differentiation of emotions, and regulatory responses are being built across childhood.

The age bias in labeling facial expressions in children: Effects of intensity and expression

Emotion reasoning, including labeling of facial expressions, is an important building block for a child's social development. This study investigated age biases in labeling facial expressions in children and adults, focusing on the influence of intensity and expression on age bias. Children (5 to 14 years old; N = 152) and adults (19 to 25 years old; N = 30) labeled happiness, disgust or sadness at five intensity levels (0%; 25%; 50%; 75%; and 100%) in facial images of children and adults. Sensitivity was computed for each of the expression-intensity combinations, separately for the child and adult faces. Results show that children and adults have an age bias at low levels of intensity (25%). In the case of sadness, children have an age bias for all intensities. Thus, the impact of the age of the face seems largest for expressions which might be most difficult to recognise. Moreover, both adults and children label most expressions best in adult rather than child faces, leading to an other-age bias in children and an own-age bias in adults. Overall, these findings reveal that both children and adults exhibit an age bias in labeling subtle facial expressions of emotions.

Sensitivity to trustworthiness cues in own- and other-race faces: The role of spatial frequency information

Research has shown that adults are better at processing faces of the most represented ethnic group in their social environment compared to faces from other ethnicities, and that they rely more on holistic/configural information for identity discrimination in own-race than other-race faces. Here, we applied a spatial filtering approach to the investigation of trustworthiness perception to explore whether the information on which trustworthiness judgments are based differs according to face race. European participants (N = 165) performed an online-delivered pairwise preference task in which they were asked to select the face they would trust more within pairs randomly selected from validated White and Asian broad spectrum, low-pass filter and high-pass filter trustworthiness continua. Results confirmed earlier demonstrations that trustworthiness perception generalizes across face ethnicity, but discrimination of trustworthiness intensity relied more heavily on the LSF content of the images for own-race faces compared to other-race faces. Results are discussed in light of previous work on emotion discrimination and the hypothesis of overlapping perceptual mechanisms subtending social perception of faces.

Group membership moderates the process of making trust judgments based on facial cues

Trust is a foundation of interpersonal communication. Faces have a significant impact on trust judgments, and separate research demonstrates that group membership also influences trust judgments. However, it remains unclear whether and how group membership moderates the effect of face trustworthiness on trust judgments and investment decisions. In the present research, two experiments were conducted to explore the moderating effect of group membership (i.e., in-group vs. out-group) on perceptions of facial trustworthiness and trust judgments. Results showed that participants invested significantly more money on trials with trustworthy faces than trials with untrustworthy faces. Additionally, there was a significant interaction between group membership and facial trustworthiness; the investment difference between trustworthy faces and untrustworthy faces was greater for trials with in-group member faces than out-group member faces. These findings indicate that top-down and bottom-up cues jointly influence behavioral decisions.

Exploring emotional face processing in 5-month-olds: The relation with quality of parent-child interaction and spatial frequencies

It is unclear whether infants differentially process emotional faces in the brain at 5 months of age. Contradictory findings of previous research indicate that additional factors play a role in this process. The current study investigated whether five-month-old infants show differential brain activity between emotional faces. Furthermore, we explored the relation between emotional face processing and (I) stimulus characteristics, specifically the spatial frequency content, and (II) parent, child, and dyadic qualities of interaction characteristics. Face-sensitive components (i.e., N290, P400, Nc) in response to neutral and fearful faces that contained only lower or higher spatial frequencies were assessed. Quality of parent-child interaction was assessed with the Manchester Assessment of Caregiver Infant Interaction (MACI). The results show that, as a full group, none of the components differed between emotional expressions. However, when splitting the group based on median MACI scores, infants who showed high quality of interaction (i.e., more attentiveness to caregiver, positive and negative affect, and liveliness) processed emotions differently, whereas infants who showed low quality did not. These results indicate that a sub-group of infants show differential emotional face processing at 5 months of age, which seem to relate to quality of their behavior during the parent-child interaction.

Is It Fear? Similar Brain Responses to Fearful and Neutral Faces in Infants with a Heightened Likelihood for Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) show atypical processing of facial expressions. Research with autistic toddlers suggests that abnormalities in processing of spatial frequencies (SFs) contribute to such differences. The current event-related-potential (ERP) study investigated differences between 10-month-old infants with high- and low-likelihood for ASD in SF processing and in discrimination of fearful and neutral faces, filtered to contain specific SF. Results indicate no group differences in general processing of higher (HSF, detailed) and lower-SF (LSF, global) information. However, unlike low-likelihood infants, high-likelihood infants do not discriminate between facial expressions when either the LSF or HSF information is available. Combined with previous findings in toddlers, the current results indicate a developmental delay in efficient processing of facial expressions in ASD.

Impression Formation in the Human Infant Brain

Forming an impression of another person is an essential aspect of human social cognition linked to medial prefrontal cortex (mPFC) function in adults. The current study examined the neurodevelopmental origins of impression formation by testing the hypothesis that infants rely on processes localized in mPFC when forming impressions about individuals who appear friendly or threatening. Infants’ brain responses were measured using functional near-infrared spectroscopy while watching 4 different face identities displaying either smiles or frowns directed toward or away from them (N = 77). This was followed by a looking preference test for these face identities (now displaying a neutral expression) using eyetracking. Our results show that infants’ mPFC responses distinguish between smiling and frowning faces when directed at them and that these responses predicted their subsequent person preferences. This suggests that the mPFC is involved in impression formation in human infants, attesting to the early ontogenetic emergence of brain systems supporting person perception and adaptive behavior.

Maternal odor reduces the neural response to fearful faces in human infants

Maternal odor is known to play an important role in mother-infant-interaction in many altricial species such as rodents. However, we only know very little about its role in early human development. The present study therefore investigated the impact of maternal odor on infant brain responses to emotional expression. We recorded the electroencephalographic (EEG) signal of seven-month-old infants watching happy and fearful faces. Infants in two control groups exposed to no specific odor (control 1) or the odor of a different infant’s mother (control 2) showed the expected EEG fear response. Crucially, this response was markedly absent in the experimental group exposed to their mother’s odor. Thus, infants respond differently to fear signals in the presence of maternal odor. Our data therefore suggest that maternal odor can be a strong modulator of social perception in human infants.

Effects of Experience on Spatial Frequency Tuning in the Visual System: Behavioral, Visuocortical, and Alpha-band Responses

Using electrophysiology and a classic fear conditioning paradigm, this work examined adaptive visuocortical changes in spatial frequency tuning in a sample of 50 undergraduate students. High-density EEG was recorded while participants viewed 400 total trials of individually presented Gabor patches of 10 different spatial frequencies. Patches were flickered to produce sweep steady-state visual evoked potentials (ssVEPs) at a temporal frequency of 13.33 Hz, with stimulus contrast ramping up from 0% to 41% Michelson over the course of each 2800-msec trial. During the final 200 trials, a selected range of Gabor stimuli (either the lowest or highest spatial frequencies, manipulated between participants) were paired with an aversive 90-dB white noise auditory stimulus. Changes in spatial frequency tuning from before to after conditioning for paired and unpaired gratings were evaluated at the behavioral and electrophysiological level. Specifically, ssVEP amplitude changes were evaluated for lateral inhibition and generalization trends, whereas change in alpha band (8-12 Hz) activity was tested for a generalization trend across spatial frequencies, using permutation-controlled F contrasts. Overall time courses of the sweep ssVEP amplitude envelope and alpha-band power were orthogonal, and ssVEPs proved insensitive to spatial frequency conditioning. Alpha reduction (blocking) was most pronounced when viewing fear-conditioned spatial frequencies, with blocking decreasing along the gradient of spatial frequencies preceding conditioned frequencies, indicating generalization across spatial frequencies. Results suggest that alpha power reduction-conceptually linked to engagement of attention and alertness/arousal mechanisms-to fear-conditioned stimuli operates independently of low-level spatial frequency processing (indexed by ssVEPs) in primary visual cortex.

Do Preverbal Infants Understand Discrete Facial Expressions of Emotion?

An ongoing debate in affective science concerns whether certain discrete, “basic” emotions have evolutionarily based signals (facial expressions) that are easily, universally, and (perhaps) innately identified. Studies with preverbal infants (younger than 24 months) have the potential to shed light on this debate. This review summarizes what is known about preverbal infants’ understanding of discrete emotional facial expressions. Overall, while many studies suggest that preverbal infants differentiate positive and negative facial expressions, few studies have tested whether infants understand discrete emotions (e.g., anger vs. disgust). Moreover, results vary greatly based on methodological factors. This review also (a) discusses how language may influence the development of emotion understanding, and (b) proposes a new developmental hypothesis for infants’ discrete emotion understanding.

Using Black Hole Algorithm to Improve EEG-Based Emotion Recognition

Emotions are a critical aspect of human behavior. One widely used technique for research in emotion measurement is based on the use of EEG signals. In general terms, the first step of signal processing is the elimination of noise, which can be done in manual or automatic terms. The next step is determining the feature vector using, for example, entropy calculation and its variations to generate a classification model. It is possible to use this approach to classify theoretical models such as the Circumplex model. This model proposes that emotions are distributed in a two-dimensional circular space. However, methods to determine the feature vector are highly susceptible to noise that may exist in the signal. In this article, a new method to adjust the classifier is proposed using metaheuristics based on the black hole algorithm. The method is aimed at obtaining results similar to those obtained with manual noise elimination methods. In order to evaluate the proposed method, the MAHNOB HCI Tagging Database was used. Results show that using the black hole algorithm to optimize the feature vector of the Support Vector Machine we obtained an accuracy of 92.56% over 30 executions.