Stimulus awareness is associated with secondary somatosensory cortex activation in an inattentional numbness paradigm.

While inattentional blindness and deafness studies have revealed neural correlates of consciousness (NCC) without the confound of task relevance in the visual and auditory modality, comparable studies for the somatosensory modality are lacking. Here, we investigated NCC using functional magnetic resonance imaging (fMRI) in an inattentional numbness paradigm. Participants (N = 44) received weak electrical stimulation on the left hand while solving a demanding visual task. Half of the participants were informed that task-irrelevant weak tactile stimuli above the detection threshold would be applied during the experiment, while the other half expected stimuli below the detection threshold. Unexpected awareness assessments after the experiment revealed that altogether 10 participants did not consciously perceive the somatosensory stimuli during the visual task. Awareness was not significantly modulated by prior information. The fMRI data show that awareness of stimuli led to increased activation in the contralateral secondary somatosensory cortex. We found no significant effects of stimulus awareness in the primary somatosensory cortex or frontoparietal areas. Thus, our results support the hypothesis that somatosensory stimulus awareness is mainly based on activation in higher areas of the somatosensory cortex and does not require strong activation in extended anterior or posterior networks, which is usually seen when perceived stimuli are task-relevant.

The effects of visual perceptual load on detection performance and event-related potentials to auditory stimuli.

Load Theory states that perceptual load prevents, or at least reduces, the processing of task-unrelated stimuli. This study systematically examined the detection and neural processing of auditory stimuli unrelated to a visual foreground task. The visual task was designed to create continuous perceptual load, alternated between low and high load, and contained performance feedback to motivate participants to focus on the visual task instead of the auditory stimuli presented in the background. The auditory stimuli varied in intensity, and participants signaled their subjective perception of these stimuli without receiving feedback. Depending on stimulus intensity, we observed load effects on detection performance and P3 amplitudes of the event-related potential (ERP). N1 amplitudes were unaffected by perceptual load, as tested by Bayesian statistics. Findings suggest that visual perceptual load affects the processing of auditory stimuli in a late time window, which is associated with a lower probability of reported awareness of these stimuli.

Visual perceptual load and processing of somatosensory stimuli in primary and secondary somatosensory cortices.

Load theory assumes that neural activation to distractors in early sensory cortices is modulated by the perceptual load of a main task, regardless of whether task and distractor share the same sensory modality or not. While several studies have investigated the question of load effects on distractor processing in early sensory areas, there is no functional magnetic resonance imaging (fMRI) study regarding load effects on somatosensory stimuli. Here, we used fMRI to investigate effects of visual perceptual load on neural responses to somatosensory stimuli applied to the wrist in a study with 44 participants. Perceptual load was manipulated by an established sustained visual detection task, which avoided simultaneous target and distractor presentations. Load was operationalized by detection difficulty of subtle or clear color changes of one of 12 rotating dots. While all somatosensory stimuli led to activation in somatosensory areas SI and SII, we found no statistically significant difference in brain activation to these stimuli under high compared to low sustained visual load. Moreover, exploratory Bayesian analyses supported the absence of differences. Thus, our findings suggest a resistance of somatosensory processing to at least some forms of visual perceptual load, possibly due to behavioural relevance of discrete somatosensory stimuli and separable attentional resources for the somatosensory and visual modality.

The effects of visual working memory load on detection and neural processing of task-unrelated auditory stimuli.

While perceptual load has been proposed to reduce the processing of task-unrelated stimuli, theoretical arguments and empirical findings for other forms of task load are inconclusive. Here, we systematically investigated the detection and neural processing of auditory stimuli varying in stimulus intensity during a stimuli-unrelated visual working memory task alternating between low and high load. We found, depending on stimulus strength, decreased stimulus detection and reduced P3, but unaffected N1 amplitudes of the event-related potential to auditory stimuli under high as compared to low load. In contrast, load independent awareness effects were observed during both early (N1) and late (P3) time windows. Findings suggest a late neural effect of visual working memory load on auditory stimuli leading to lower probability of reported awareness of these stimuli.

Differential effects of prediction error and adaptation along the auditory cortical hierarchy during deviance processing.

Neural mismatch responses have been proposed to rely on different mechanisms, including prediction error-related activity and adaptation to frequent stimuli. However, the hierarchical cortical structure of these mechanisms is unknown. To investigate this question, we recorded hemodynamic responses while participants (N = 54) listened to an auditory oddball sequence as well as a suited control condition. In addition to effects in sensory processing areas (Heschl's gyrus, superior temporal gyrus (STG)), we found several distinct clusters that indexed deviance processing in frontal and parietal regions (anterior cingulate cortex/supplementary motor area (ACC/SMA), inferior parietal lobule (IPL), anterior insula (AI), inferior frontal junction (IFJ)). Comparing responses to the control stimulus with the deviant and standard enabled us to delineate the contributions of prediction error- or adaptation-related brain activation, respectively. We observed significant effects of adaptation in Heschl's gyrus, STG and ACC/SMA, while prediction error-related activity was observed in STG, IPL, AI and IFJ. Additional dynamic causal modeling confirmed the superiority of a hierarchical processing structure compared to a flat structure. Thus, we found that while prediction-error related processes increased with the hierarchical level of the brain area, adaptation declined. This suggests that the relative contribution of different mechanisms in deviance processing varies across the cortical hierarchy.

No trait anxiety influences on early and late differential neuronal responses to aversively conditioned faces across three different tasks.

The human brain's ability to quickly detect dangerous stimuli is crucial in selecting appropriate responses to possible threats. Trait anxiety has been suggested to moderate these processes on certain processing stages. To dissociate such different information-processing stages, research using classical conditioning has begun to examine event-related potentials (ERPs) in response to fear-conditioned (CS +) faces. However, the impact of trait anxiety on ERPs to fear-conditioned faces depending on specific task conditions is unknown. In this preregistered study, we measured ERPs to faces paired with aversive loud screams (CS +) or neutral sounds (CS -) in a large sample (N = 80) under three different task conditions. Participants had to discriminate face-irrelevant perceptual information, the gender of the faces, or the CS category. Results showed larger amplitudes in response to aversively conditioned faces for all examined ERPs, whereas interactions with the attended feature occurred for the P1 and the early posterior negativity (EPN). For the P1, larger CS + effects were observed during the perceptual distraction task, while the EPN was increased for CS + faces when deciding about the CS association. Remarkably, we found no significant correlations between ERPs and trait anxiety. Thus, fear-conditioning potentiates all ERP amplitudes, some processing stages being further modulated by the task. However, the finding that these ERP differences were not affected by individual differences in trait anxiety does not support theoretical accounts assuming increased threat processing or reduced threat discrimination depending on trait anxiety.

Increased early and late neuronal responses to aversively conditioned faces across different attentional conditions.

Faces with emotional information-by virtue of their expression or their history of affective learning-are prioritized during neuronal processing as compared to neutral faces. Classical conditioning studies have shown that aversively conditioned (CS+) faces potentiate different face processing stages as evidenced by increased early and late event-related potential (ERPs) components. However, it is unknown whether and how ERP modulations depend on certain attentional conditions. To examine this question, this preregistered study investigated ERPs to faces paired with aversive screams or neutral sounds under three tasks with increasing attention to CS + relevant features of the face: Participants (N = 40) had to discriminate either the orientation of superimposed lines, perceived gender, or the CS association. We found potentiation of the N170, the Early Posterior Negativity (EPN), and, most remarkably, the Late Positive Potential (LPP) to CS + faces regardless of task condition. This finding suggests that, in contrast to other types of emotional information and learning, classical conditioning boosts early and late processing stages, even if no explicit attention to the face information or the CS association is required.

Charged With a Crime: The Neuronal Signature of Processing Negatively Evaluated Faces Under Different Attentional Conditions.

Our brains rapidly respond to human faces and can differentiate between many identities, retrieving rich semantic emotional-knowledge information. Studies provide a mixed picture of how such information affects event-related potentials (ERPs). We systematically examined the effect of feature-based attention on ERP modulations to briefly presented faces of individuals associated with a crime. The tasks required participants (N = 40 adults) to discriminate the orientation of lines overlaid onto the face, the age of the face, or emotional information associated with the face. Negative faces amplified the N170 ERP component during all tasks, whereas the early posterior negativity (EPN) and late positive potential (LPP) components were increased only when the emotional information was attended to. These findings suggest that during early configural analyses (N170), evaluative information potentiates face processing regardless of feature-based attention. During intermediate, only partially resource-dependent, processing stages (EPN) and late stages of elaborate stimulus processing (LPP), attention to the acquired emotional information is necessary for amplified processing of negatively evaluated faces.

Let's Talk About Each Other: Neural Responses to Dissenting Personality Evaluations Based on Real Dyadic Interactions.

Dyadic interactions are associated with the exchange of personality-related messages, which can be congruent or incongruent with one's self-view. In the current preregistered study (N = 52), we investigated event-related potentials (ERPs) toward real social evaluations in order to uncover the neural mechanisms underlying the processing of congruent and incongruent evaluative feedback. Participants interacted first, and then during an electroencephalogram (EEG) session, they received evaluations from their interaction partner that were either congruent or incongruent with their own ratings. Findings show potentiated processing of self-related incongruent negative evaluations at early time points (N1) followed by increased processing of both incongruent negative and positive evaluations at midlatency time windows (early posterior negativity) and a prioritized processing of self-related incongruent positive evaluations at late time points (feedback-related P3, late positive potential). These findings reveal that, after real social interactions, evaluative feedback about oneself that violates one's self-view modulates all processing stages with an early negativity and a late positivity bias.

Electrophysiological responses to negative evaluative person-knowledge: Effects of individual differences.

Faces transmit rich information about a unique personal identity. Recent studies examined how negative evaluative information affects event-related potentials (ERPs), the relevance of individual differences, such as trait anxiety, neuroticism, or agreeableness, for these effects is unclear. In this preregistered study, participants (N = 80) were presented with neutral faces, either associated with highly negative or neutral biographical information. Faces were shown under three different task conditions that varied the attentional focus on face-unrelated features, perceptual face information, or emotional information. Results showed a task-independent increase of the N170 component for faces associated with negative information, while interactions occurred for the Early Posterior Negativity (EPN) and the Late Positive Potential (LPP), showing ERP differences only when paying attention to the evaluative information. Trait anxiety and neuroticism did not influence ERP differences. Low agreeableness increased EPN differences during perceptual distraction. Thus, we observed that low agreeableness leads to early increased processing of potentially hostile faces, although participants were required to attend to a face-unrelated feature.

Bayes Factors show evidence against systematic relationships between the anchoring effect and the Big Five personality traits.

Examining personality traits as predictors of human behaviour is of high interest. There are several but inconclusive reported relationships of personality and the susceptibility to the "anchoring effect", a tendency to adjust estimates towards a given anchor. To provide an answer to variably reported links between personality traits and the anchoring effect, we collected data from 1000 participants in the lab and validated typical anchoring effects and representative personality scores of the sample. Using Bayesian statistical data analyses, we found evidence for the absence of a relationship between anchoring effects and personality scores. We, therefore, conclude that there are no specific personality traits that relate to a higher susceptibility to the anchoring effect. The lack of a relationship between personality and the susceptibility to the anchoring effect might be due to the specific anchoring design, be limited to specific cognitive domains, or the susceptibility to anchors might reflect no reliable individual cognitive phenomena. In the next step, studies should examine the reliability of anchoring effects on the individual level, and testing relationships of individual traits and anchoring effects for other types of anchors, anchoring designs, or cognitive domains.

Reduced early fearful face processing during perceptual distraction in high trait anxious participants.

Fearful facial expressions are prioritized across different stages of information processing as reflected by early, mid-latency, and late components of event-related brain potentials (ERP). Trait anxiety has been proposed to modulate these responses, but it is yet unclear how such modulations depend on feature-based attention. In this preregistered study (N = 80), we investigated the effects of trait anxiety on ERP differences between fearful and neutral faces across three different tasks. Participants had to discriminate either the orientation of lines overlaid onto the faces, the gender of the face, or the emotional expression, thus increasing attention to emotionally relevant facial features across the tasks. Fearful versus neutral faces elicited increased P1 and N170 amplitudes across tasks and potentiated amplitudes when attention was directed to faces (early posterior negativity [EPN]) or the expression (EPN and late positive potential). Higher trait anxiety was related to smaller EPN differences between fearful and neutral faces during the perceptual discrimination task. This early relationship suggests reduced instead of amplified processing of fearful faces for high trait anxious participants under perceptual distraction.

Effects of low-level visual information and perceptual load on P1 and N170 responses to emotional expressions.

Emotional facial expressions lead to modulations of early event-related potentials (ERPs). However, it has so far remained unclear how far these modulations represent face-specific effects rather than differences in low-level visual features, and to which extent they depend on available processing resources. To examine these questions, we conducted two preregistered independent experiments (N = 40 in each experiment) using different variants of a novel task that manipulates peripheral perceptual load across levels but keeps overall visual stimulation constant. At the display center, we presented task-irrelevant angry, neutral, and happy faces and their Fourier phase-scrambled versions, which preserved low-level visual features. The results of both studies showed load-independent P1 and N170 emotional expression effects. Importantly, by using Bayesian analyses we could confirm that these facial expression effects were face-independent for the P1 but not for the N170 component. We conclude that firstly, ERP modulations during the P1 interval strongly depend on low-level visual information, while the N170 modulation requires the processing of figural facial expression features. Secondly, both P1 and N170 modulations appear to be immune to a large range of variations in perceptual load.

Attentional conditions differentially affect early, intermediate and late neural responses to fearful and neutral faces.

The processing of fearful facial expressions is prioritized by the human brain. This priority is maintained across various information processing stages as evident in early, intermediate and late components of event-related potentials (ERPs). However, emotional modulations are inconsistently reported for these different processing stages. In this pre-registered study, we investigated how feature-based attention differentially affects ERPs to fearful and neutral faces in 40 participants. The tasks required the participants to discriminate either the orientation of lines overlaid onto the face, the sex of the face or the face's emotional expression, increasing attention to emotion-related features. We found main effects of emotion for the N170, early posterior negativity (EPN) and late positive potential (LPP). While N170 emotional modulations were task-independent, interactions of emotion and task were observed for the EPN and LPP. While EPN emotion effects were found in the sex and emotion tasks, the LPP emotion effect was mainly driven by the emotion task. This study shows that early responses to fearful faces are task-independent (N170) and likely based on low-level and configural information while during later processing stages, attention to the face (EPN) or-more specifically-to the face's emotional expression (LPP) is crucial for reliable amplified processing of emotional faces.

Time-dependent effects of perceptual load on processing fearful and neutral faces.

High perceptual load is thought to impair the early processing of task-irrelevant distractors. In contrast, for emotional faces, previous studies have shown that early event-related potentials (ERPs), the P1, the N170, and, albeit to a lesser degree, the EPN, are relatively resistant to perceptual load manipulations. However, the temporal dynamics of the interaction between load and processing of emotional distractor faces have been neglected so far. In this preregistered EEG study (N = 40), we investigated effects of perceptual load and different interstimulus intervals (ISIs) on ERPs to fearful and neutral task-irrelevant faces. We used a task with identical visual input regardless of perceptual load (high vs. low), and four ISIs between task and face onset (100 ms, 300 ms, 600 ms, 900 ms). Results show that emotional ERP modulations depend on load manipulations as well as on specific ISIs between the perceptual task and face onset. Emotional P1 effects were modulated by load, irrespective of the ISI, while emotional N170 and EPN effects were independent of load, but modulated by the ISI. In particular, emotion effects for the EPN were only observed after a prolonged period between load task and face onset (ISI900), suggesting a strong vulnerability of this component to any competing task. Taken together, our findings show that early ERP components for fearful expressions show dissociable responses to load and timing manipulations.

Nonlinear Effects of Linearly Increasing Perceptual Load on ERPs to Emotional Pictures.

The prioritized processing of emotional as compared to neutral stimuli is reflected in enlarged event-related potentials (ERPs). However, perceptual load theory proposes that under conditions of high perceptual load, information processing is attenuated or abolished. The parametrical effects of load on ERPs to emotional pictures are unknown. To shed light on this question, the current preregistered ERP study (N = 30) systematically investigated the effects of load on ERPs to task-irrelevant negative, neutral, and positive pictures. Crucially, while perceptual input was held constant, perceptual load was systematically manipulated so that it increased linearly across 4 load levels, which was evident in behavioral data. In contrast, load effects on ERP differences between emotional and neutral stimuli did not follow a linear function. For the N1, early posterior negativity and late positive potential, a nonlinear function with reversed emotion effects at the third load level provided the best fit. These findings do not only show that perceptual load attenuates emotional picture processing but also suggest that active processes are initiated to reduce distraction by emotional information. Moreover, these effects of perceptual load on emotional ERP components appear to deviate from theoretically expected functions.