Enhanced N170 Amplitudes Research Articles

Perceptual load-independent modulation of the facilitated processing of emotional eye regions

Although the eye region has been found to convey sufficient information for emotional recognition and interpersonal communication, little is known regarding the extent to which the prioritized processing of emotional eye regions relies on available attentional resources. To address this issue, the present study used a dual-target rapid serial visual presentation task in which the perceptual load levels of the first target (T1), as well as the valence of the second target (T2), were manipulated. In addition to the traditional event-related potential (ERP) analysis method, the mass univariate statistics approach was employed. Behaviorally, both happy and fearful eye regions were recognized more accurately than neutral eye regions, regardless of the T1 perceptual load. ERP findings revealed an enhanced N170 amplitude for fearful eye regions compared to neutral eye regions, confirming the preferential and automatic processing of fearful signals at the early sensory stage. The late positive potential component exhibited enhanced responses to fearful and happy eye regions, suggesting the amplified representation consolidation in working memory. Collectively, these findings indicate that isolated eye regions are processed automatically to a higher degree owing to their perceptual and motivational significance.

Effects of aging on face processing: An ERP study of the own-age bias with neutral and emotional faces

Older adults systematically show an enhanced N170 amplitude during the visualization of facial expressions of emotion. The present study aimed to replicate this finding, further investigating if this effect is specific to facial stimuli, present in other neural correlates of face processing, and modulated by own-age faces. To this purpose, younger (n=25; Mage=28.36), middle-aged (n=23; Mage=48.74), and older adults (n=25; Mage=67.36) performed two face/emotion identification tasks during an EEG recording. The results showed that groups did not differ regarding P100 amplitude, but older adults had increased N170 amplitude for both facial and non-facial stimuli. The event-related potentials analysed were not modulated by an own-age bias, but older faces elicited larger N170 in the Emotion Identification Task for all groups. This increased amplitude may reflect a higher ambiguity of older faces due to age-related changes in their physical features, which may elicit higher neural resources to decode. Regarding P250, older faces elicited decreased amplitudes than younger faces, which may reflect a reduced processing of the emotional content of older faces. This interpretation is consistent with the lower accuracy obtained for this category of stimuli across groups. These results have important social implications and suggest that aging may hamper the neural processing of facial expressions of emotion, especially for own-age peers.

Asynchronous neural oscillations associated with subliminal affective face priming in autism spectrum disorder.

Autism spectrum disorder (ASD) is characterized by social communicative disturbance. Social communication requires rapid processing and accurate cognition regarding others' emotional expressions. Previous electrophysiological studies have attempted to elucidate the processes underlying atypical face-specific N170 responses to emotional faces in ASD. The present study explored subliminal affective priming effects (SAPEs) on the N170 response and time-frequency analysis of intertrial phase coherence (ITPC) for the N170 in ASD. Fifteen participants [seven participants with ASD and eight typically developing (TD) controls] were recruited for the experiment. Event-related potentials were recorded with a 128-channel electroencephalography device while participants performed an emotional face judgment task. The results revealed enhanced N170 amplitude for supraliminal target-face stimuli when they were preceded by subliminal fearful-face stimuli, in both the ASD and TD groups. Interestingly, TD participants exhibited higher alpha-ITPC in the subliminal fearful-face priming condition in the right face-specific area in the N170 time window. In contrast, there were no significant differences in ITPC in any frequency bands between the subliminal fearful and neutral priming conditions in the ASD group. Asynchronous phase-locking neural activities in the face-specific area may underlie impaired nonconscious face processing in ASD, despite the presence of common features of SAPEs for the N170 component in both the ASD and TD groups.

Enhanced contralateral theta oscillations and N170 amplitudes in occipitotemporal scalp regions underlie attentional bias to fearful faces

Attending toward fearful faces and other threatening stimuli increase the chance of survival. The dot-probe task is a commonly used measure of spatial attention. Event-related potentials (ERPs) have been found to be a reliable measure of attentional bias. The dot-probe literature suggests that posterior contralateral N170 amplitudes are more enhanced by fearful faces compared to ipsilateral amplitudes. However, ERP methods remove non-phase locked frequencies, which provides additional information about neural activity. Specifically, theta oscillations (5–7 Hz) have been linked to attentional processing. The purpose of this study was to examine the relationship between posterior contralateral theta oscillations and N170 amplitudes in the dot-probe task. A modified dot-probe task was used with fear and neutral facial expressions and EEG data was recorded from 33 electrodes. The ERP and time-frequency data were extracted from the P7 and P8 electrodes (left and right occipitotemporal regions). This study found enhanced N170 amplitude and theta oscillations in the electrodes posterior contralateral to the fearful face. Contralateral N170 amplitudes and theta oscillations were related such that greater N170 amplitudes were associated with greater theta oscillations. The results indicated that increased contralateral N170 and theta oscillations are related to each other and underlie attentional bias to fearful faces.

Turning the Face Inversion Effect on Its Head: Violated Expectations of Orientation, Lighting, and Gravity Enhance N170 Amplitudes.

Face inversion effects occur for both behavioral and electrophysiological responses when people view faces. In EEG, inverted faces are often reported to evoke an enhanced amplitude and delayed latency of the N170 ERP. This response has been attributed to the indexing of specialized face processing mechanisms within the brain. However, inspection of the literature revealed that, although N170 is consistently delayed to a variety of face representations, only photographed faces invoke enhanced N170 amplitudes upon inversion. This suggests that the increased N170 amplitudes to inverted faces may have other origins than the inversion of the face's structure. We hypothesize that the unique N170 amplitude response to inverted photographed faces stems from multiple expectation violations, over and above structural inversion. For instance, rotating an image of a face upside-down not only violates the expectation that faces appear upright but also lifelong priors about illumination and gravity. We recorded EEG while participants viewed face stimuli (upright vs. inverted), where the faces were illuminated from above versus below, and where the models were photographed upright versus hanging upside-down. The N170 amplitudes were found to be modulated by a complex interaction between orientation, lighting, and gravity factors, with the amplitudes largest when faces consistently violated all three expectations. These results confirm our hypothesis that face inversion effects on N170 amplitudes are driven by a violation of the viewer's expectations across several parameters that characterize faces, rather than a disruption in the configurational disposition of its features.

Adult processing of child emotional expressions: A meta-analysis of ERP studies.

Numerous event-related potential (ERP) studies have examined adults' neural responses to child emotional expressions to understand the neurobiological mechanisms contributing to caregiving. It is unclear, however, whether one emotion evokes an enhanced response across components, and whether this pattern differs based on parent status or other sample characteristics. This meta-analysis quantified adult responses to child emotional expressions at the N170 and the late positive potential (LPP) components. Cohen's d reflected the difference between crying and neutral (CN), crying and laughing (CL), and laughing and neutral (LN) N170 and LPP amplitudes. Crying expressions elicited slightly enhanced N170 and LPP amplitudes relative to neutral and laughing expressions (N170 CN: k = 24, d = -0.09, p < 0.001; N170 CL: k = 30, d = -0.07, p = .004; LPP CN: k = 20, d = 0.12, p = .027; LPP CL: k = 27, d = 0.10, p < .001), and laughing expressions elicited slightly enhanced N170 amplitudes relative to neutral expressions (N170 LN: k = 21, d = -0.05, p = .02). Parental status, child age, risk factors for insensitive caregiving, and measurement characteristics moderated some effect sizes, with reference electrode emerging as the most consistent moderator. Results shed light on the typical pattern of neural response to child emotions and characteristics that may moderate this response. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

When noise is beneficial for sensory encoding: Noise adaptation can improve face processing

The presence of noise usually impairs the processing of a stimulus. Here, we studied the effects of noise on face processing and show, for the first time, that adaptation to noise patterns has beneficial effects on face perception. We used noiseless faces that were either surrounded by random noise or presented on a uniform background as stimuli. In addition, the faces were either preceded by noise adaptors or not. Moreover, we varied the statistics of the noise so that its spectral slope either matched that of the faces or it was steeper or shallower. Results of parallel ERP recordings showed that the background noise reduces the amplitude of the face-evoked N170, indicating less intensive face processing. Adaptation to a noise pattern, however, led to reduced P1 and enhanced N170 amplitudes as well as to a better behavioral performance in two of the three noise conditions. This effect was also augmented by the presence of background noise around the target stimuli. Additionally, the spectral slope of the noise pattern affected the size of the P1, N170 and P2 amplitudes. We reason that the observed effects are due to the selective adaptation of noise-sensitive neurons present in the face-processing cortical areas, which may enhance the signal-to-noise-ratio.

Classification of Emotional Expressions Is Affected by Inversion: Behavioral and Electrophysiological Evidence.

It has been shown that emotionally positive facial expressions are recognized substantially faster than emotionally negative facial expressions, the positive classification advantage (PCA). In this experiment we explored the involvement of configural computations while processing positive and negative faces in an expression categorization task using artificial faces. Analyzing the reaction times (RTs), we found that happy faces were categorized more quickly than sad faces (PCA) and this effect disappeared for inverted faces. Event-related potentials (ERPs) data showed that the face-sensitive N170 component was larger for sad than for happy faces only at upright condition and that face inversion significantly enhanced N170 amplitudes only for happy faces. Moreover, the happy faces elicited shorter N170 latency than did the sad faces, whereas for inverted condition the N170 latency did not differ between happy and sad faces. Finally, the significant positive correlation between the RTs and the latency of the N170 was not found for N170 amplitudes. Because the configural computation was task-irrelevant in the present study, these behavioral and ERP data indicated that one of the sources of PCA is the configural analysis applied by default while categorizing facial emotions.

Which feature is fixated modulates the N170 regardless of facial expression

Facial expressions represent an important part of non-verbal communication used in everyday life. The N170 is widely regarded as a face-sensitive potential and has been linked to facial structural encoding, however it remains debated whether the N170 is modulated by facial expressions of emotion. We investigated how attention to facial features affects the early stages of emotion perception during an implicit emotion processing task. ERPs were recorded in response to presentations of fearful, joyful, or neutral facial expressions while fixation was restricted to the left eye, right eye, nose, or mouth using an eye tracker. Participants’ task was to discriminate the face gender. Enhanced N170 amplitudes and longer latencies were found when participants were fixated on the left and right eyes compared to the mouth and nose irrespective of emotion. Importantly, the N170 was not modulated by emotion. The results support the view that the N170 component is not sensitive to the facial expression in an implicit emotional task. In contrast, which feature is fixated modulates this component. As the eyes have been shown to be the diagnostic feature used to correctly categorize face gender, it could be that attention to the diagnostic feature is what drives N170 modulation with emotion in previous studies not controlling for fixation. This idea is currently being tested using an explicit emotional task with the same stimuli. Meeting abstract presented at VSS 2013

Behavioral and electrophysiological correlates of intact and scrambled body perception

ObjectiveIntact faces and bodies elicit two prominent electrophysiological components (P100 and N170). The N170 is thought to be related to the structural encoding and configural processing of faces and bodies. The aim of the present study was to investigate whether intact faces and bodies as well as scrambled faces and bodies elicit the same component. This would imply that similar as faces, bodies are encoded as a whole. MethodsWe used a matching to sample task and two manipulations validated as an assessment of configural processing in previous studies: the inversion effect and intact versus scrambled stimulus presentation. ResultsFor both categories, performance was better for intact compared to scrambled stimuli. Additionally, stimulus distortion seems to abolish the body but not the face inversion effect. On the electrophysiological level, we found enhanced N170 amplitudes for intact faces and bodies compared to scrambled stimuli. The opposite pattern engaged in the time-window of the P100. Furthermore, for the N170 we observed an inversion effect for intact but not scrambled bodies. ConclusionsFirst-order relational information are important for the perception of bodies and might be processed in the N170 time-window. Disrupting this information interacts with the inversion effect. SignificanceThe current data suggest that faces and bodies might be processed by distinct mechanisms as the experimental manipulation affected faces in a different way than bodies.

The face-sensitive N170 component in developmental prosopagnosia

Individuals with developmental prosopagnosia (DP) show severe face recognition deficits in the absence of any history of neurological damage. To examine the time-course of face processing in DP, we measured the face-sensitive N170 component of the event-related brain potential (ERP) in a group of 16 participants with DP and 16 age-matched control participants. Reliable enhancements of N170 amplitudes in response to upright faces relative to houses were found for the DP group. This effect was equivalent in size to the effect observed for controls, demonstrating normal face-sensitivity of the N170 component in DP. Face inversion enhanced N170 amplitudes in the control group, but not for DPs, suggesting that many DPs do not differentiate between upright and inverted faces in the typical manner. These N170 face inversion effects were present for younger but not older controls, while they were absent for both younger and older DPs. Results suggest that the early face-sensitivity of visual processing is preserved in most individuals with DP, but that the face processing system in many DPs is not selectively tuned to the canonical upright orientation of faces.

Influence of the OPRM1 gene polymorphism upon children's degree of withdrawal and brain activation in response to facial expressions

Genetic variation of the A118G polymorphism of the μ-opioid receptor gene (OPRM1) predicts individual sensitivity to social rejection and fMRI activation during simulated social rejection in adults, while data on these relationships during childhood are lacking. We investigated whether this polymorphism predicts childhood withdrawal – a predictor of sensitivity to social rejection –, and the face-specific N170 event-related waveform in response to facial expressions. Among facial expressions, ‘anger’ was expected to be particularly evocative, as it communicates social rejection.Forty-nine children aged 8–10 years were characterised for their OPRM1 genotype, their score at the Withdrawn Scale of the Child Behavior Checklist (CBCL), and for N170 latencies and amplitudes recorded during a task of implicit processing of happy, neutral, and angry expressions of other children. Children carrying the OPRM1-G allele had higher CBCL Withdrawn scores and enhanced N170 amplitudes in response to facial expressions. Multiple linear regressions showed that the Withdrawn scale score predicts larger N170 amplitudes at the Pz and C4 electrodes, only for the anger expression.Children who carry one or two copies of the OPRM1 G-allele are more likely to manifest withdrawn behaviours, and differ for electrophysiological responses to the early phases of processing affective stimuli.

Gender differences in face recognition: A behavioral and ERP study

The present study examined gender differences in face recognition using the “learning-recognition” paradigm in conjunction with behavioral and event-related potential (ERP) analysis. The results revealed four major findings: (1) Female faces were easier to remember than male faces, and females remembered more faces than males. (2) We observed a familiarity effect at 170 ms after stimulus onset (NI70), with larger amplitudes in response to familiar faces, indicating that the N170 can be modulated by familiarity. (3) Enhanced N170 amplitude was observed for female faces, possibly because the female faces involved more changeable features, meaning that recognition entailed a greater cognitive load. Enhanced P2 amplitude was observed in response to male faces, possibly because the male faces involved less changeable features, meaning that they were more difficult to recognize and required deeper processing. (4) Increased P1 amplitude was exhibited in response to familiar compared to unfamiliar faces by females, but not by males. This result suggests that females processed the familiarity of faces earlier than males. In addition, differences in P2 and N250 amplitude were observed between familiar and unfamiliar faces in females. The familiar/unfamiliar effect in females was associated with a broader area of scalp activation, compared to males. Taken together, our electrophysiological findings suggested that females possess superior face recognition ability.

Face-related ERPs are modulated by point of gaze

This study examined the influence of gaze fixation on face-sensitive ERPs. A fixation crosshair presented prior to face onset directed visual attention to upper, central, or lower face regions while ERPs were recorded. This manipulation modulated a face-sensitive component (N170) but not an early sensory component (P1). Upper and lower face fixations elicited enhanced N170 amplitude and longer N170 latency. Results expand upon extant hemodynamic research by demonstrating early effects at basic stages of face processing. These findings distinguish attention to facial features in context from attention to isolated features, and they inform electrophysiological studies of face processing in clinical populations.

Using spatial frequency scales for processing face features and face configuration: An ERP analysis

In the present study we examined the influence of spatial filtering on the N170-effect, a relatively early face-selective ERP difference associated with face detection. We compared modulation of the N170-effect using spatially filtered stimuli that either facilitated feature analysis or impeded configural analysis. The salience of inner face components was enhanced by presenting them in isolation. Configural processing was manipulated by face inversion. The N170-effects elicited by upright faces and isolated inner components were similar across low- and high-spatial frequency scales. In contrast, the inversion effect (enhanced N170 amplitude for inverted compared with upright faces) was only observed with broadband and low-spatial frequency stimuli. These findings demonstrate that the N170-effect can be influenced by both low- and high-spatial frequency channels. Moreover, they indicate that different configural manipulations (isolated features vs. face inversion) affect face detection in distinct ways, consistent with separate processing mechanisms for different types of configural encoding.

Animal and human faces in natural scenes: How specific to human faces is the N170 ERP component?

The N170 is an event-related potential component reported to be very sensitive to human face stimuli. This study investigated the specificity of the N170, as well as its sensitivity to inversion and task status when subjects had to categorize either human or animal faces in the context of upright and inverted natural scenes. A conspicuous N170 was recorded for both face categories. Pictures of animal faces were associated with a N170 of similar amplitude compared to pictures of human faces, but with delayed peak latency. Picture inversion enhanced N170 amplitude for human faces and delayed its peak for both human and animal faces. Finally, whether processed as targets or non-targets, depending on the task, both human and animal face N170 were identical. Thus, human faces in natural scenes elicit a clear but non-specific N170 that is not modulated by task status. What appears to be specific to human faces is the strength of the inversion effect.