The more you ignore me the closer I get: An ERP study of evaluative priming

Electrophysiological correlates of semantic pain processing in the affective priming

Introduction

Pain plays a fundamental role in the well-being of the individual, and its semantic content may have specific properties compared to other negative domains (i.e., fear and anger) which allows the cognitive system to detect it with priority. Considering the influence of the affective context in which stimuli (targets) are evaluated, it is possible that their valence could be differentially processed if preceded by negative stimuli (primes) associated with pain than negative stimuli not associated with pain. Thus, the present study aims to investigate the electrophysiological correlates of the implicit processing of words with pain content by using an affective priming paradigm.

Methods

Event-related potentials (ERPs) were recorded while participants were presented with positive and negative word targets (not associated with pain) that were preceded by positive, negative (not associated with pain), and pain word primes. Participants were asked to judge the valence of the target word.

Results

Results showed faster reaction times (RTs) in congruent conditions, especially when the negative target was preceded by a pain prime rather than a positive one. ERPs analyses showed no effect of pain at an early-stage processing (N400), but a larger waveform when the pain prime preceded the positive prime on the LPP.

Discussion

These results reaffirm the importance that valence has in establishing the priority with which stimuli are encoded in the environment and highlight the role that pain has in the processing of stimuli, supporting the hypothesis according to which the valence and the semantics of a stimulus interact with each other generating a specific response for each type of emotion.

Attention to affect 2.0: Multiple effects of emotion and attention on event-related potentials of visual word processing in a valence-detection task

Here we continue recent work on the specific mental processes engaged in a valence-detection task. Fifty-seven participants responded to one predefined target level of valence (negative, neutral, or positive), and ignored the remaining two levels. This enables more precise fine-tuning of neuronal pathways, compared to valence categorization where attention is divided between different levels of valence. Our group recently used valence detection with emotional words. Posterior P1 and N170 effects in the event-related potential (ERP) supported the idea of valent word forms that can be tuned by selective attention to valence. Here we report findings on three distinct posterior N2 components, P300, N400, and the late positive potential (LPP). Target but not nontarget words showed an arousal effect (emotional > neutral) on left-side early posterior negativity (180-280 ms). In contrast, an arousal effect on a sharp N2 deflection in left-minus-right difference ERPs (230-270 ms), suggesting facilitation of lexical access for emotional words, was independent of target status. This also applied to increased medial parieto-occipital N2 (260-300 ms) specific to negative words, indicating attentional capture. Medial-central N400 was specifically enhanced for negative nontarget words, further supporting attentional capture. The typical LPP arousal effect was observed, being stronger and more left-lateralized in target words. An exploratory finding concerned a broad component-overarching ERP valence effect (250-650 ms). Independent of target status, ERPs were more positive for positive than negative words. Combined with our previous results, data suggest multiple loci of emotion-attention interactions in valence detection.

Subliminal affective priming effect: Dissociated processes for intense versus normal facial expressions

Positive vs. negative intense-facial expressions are difficult to explicitly distinguish; yet, whether they dissociate when subliminally presented remains unclear. Through three experiments using affective priming paradigms, we assessed how intense facial expressions, when presented briefly (17 ms) and masked, influenced following neutral ambiguous words (Experiment 1) or visible facial expressions (Experiments 2&3). We also compared these results with those of using normal facial expressions as primes in each experiment. All experiments indicated masked affective priming effects (biasing valence judgement of neutral words or facilitating reaction time to faces with the same valence as the prime) in normal facial expression, but not those intense ones. Experiment 3 using event related potentials (ERPs) further revealed that two ERP components N250 and LPP were consistent with behavioral changes in the normal condition (larger when valences of primes and targets were different), but inconsistent in the intense condition. Taken together, our results provided behavioral and neural evidence for distinctive processing between normal and intense facial expressions under masked condition.

Attention please: ERP evidence for prime-target resource competition in the neutral-target variant of affective priming

Using event-related potentials we examined the mechanisms that underlie the influence of affective context information on evaluative judgments in affective priming (AP). Participants (N = 44) evaluated a priori neutral target ideographs that were preceded by 800-ms negative, neutral or positive prime pictures. We observed a significant AP effect (APE), with more positive target ratings for targets following positive versus negative primes, with neutral primes lying in between. A greater individual APE was associated with increased attention for the primes, indicated by larger amplitudes of parietal positive slow wave (PSW) and more pronounced prime affect discrimination mirrored in affect-specific variations of parieto-occipital prime P1 and parietal prime P2, P300, and PSW amplitudes. This confirms previous theoretical and empirical work suggesting that the size of the APE critically depends on the extent of prime-elicited affective activation. Furthermore, a greater individual APE was related to generally reduced depth of target processing as mirrored in smaller overall amplitudes of attention-sensitive target-related P1, P2, P300, and PSW. In addition, in the total sample P2, P300, and PSW were smaller for targets following AP eliciting, attention-capturing emotional, as compared to neutral primes. Based on the observed coincidence of increased processing of affective versus neutral primes, and specifically reduced processing of those targets that followed affective primes, we propose prime-target resource competition as an additional, not yet described process contributing to AP in the neutral-target paradigm.

Independent ERP predictors of affective priming underline the importance of depth of prime and target processing and implicit affect misattribution

We used event-related potentials (ERPs) to investigate the mental processes that contribute to affective priming (AP), a systematic shift of evaluative judgments about neutral targets toward the valence of preceding primes. 64 participants rated their liking of a priori neutral ideographs preceded by 800-ms emotional primewords, while 64-channel EEG was recorded. We observed a significant AP effect that was closely associated with prime valence dependent variations of the right central-to-parieto-occipital positive slow wave (PSW) amplitude in the target ERP, providing evidence for implicit affect misattribution as one source of the effect. While deeper target processing mirrored in valence unspecific central-to-parieto-occipital target PSW amplitude was negatively associated with AP, deeper prime processing indicated by valence unspecific central-to-parieto-occipital prime PSW amplitude was positively related to AP. These depth of processing effects underline the importance of strategic processes in AP. In a stepwise linear regression analysis, the prime valence effect on right central-to-parieto-occipital target PSW indicating affect misattribution and the two valence-unspecific ERP indices of processing depth (central-to-parieto-occipital prime- and target PSW) were independent predictors of the size of the AP effect. Together they accounted for 60% of the variance. Furthermore, an explorative analysis provided first evidence for the relevance of early discrimination of prime valence for AP.

On ignoring words-exploring the neural signature of inhibition of affective words using ERPs

In the present study event-related potentials were used to shed further light on the neural signatures of active inhibition of the (affective) content of written words. Intentional inhibition was implemented by simply asking participants (N = 32) to ignore single words that served as primes in an affective priming (AP) task. In AP, evaluations about a priori neutral targets typically tend to shift towards the valence of preceding primes, denoting an AP effect (APE). To create a plausible cover-context emphasizing the usefulness of word inhibition, participants were asked to avoid this shift, that is, to make unbiased target evaluations. Ignoring the prime words was suggested as the most efficient strategy to achieve this aim. Effective inhibition of the words' (affective) content, as suggested by a significant APE present for words processed without any further instruction, but not for ignored ones, affected multiple stages of processing. On the neuronal level, word inhibition was characterized by reduced early perceptual (left-lateralized word-specific N170), later attentional (parietal P300), and affective-semantic processing (reduced posterior semantic asymmetry). Furthermore, an additional recruitment of top-down inhibitory control processes, which was mirrored in increased amplitudes of medial-frontal negativity, showed to be critically involved in intentional word inhibition.

Lexical Processing as Revealed by Lateralized Event-Related Brain Potentials

Abstract. Neurocognitive models of written-word processing from low-level perceptual up to semantic analysis include the notion of a strongly left-lateralized posterior-to-anterior stream of activation. Two left-lateralized components in the event-related brain potential (ERP), N170 and temporo-parietal PSA (posterior semantic asymmetry; peak at 300 ms), have been suggested to reflect sublexical analysis and semantic processing, respectively. However, for intermediate processing steps, such as lexical access, no posterior left-lateralized ERP signature has yet been observed under single-word reading conditions. In combination with a recognition task, lexicality and depth of processing were varied. Left-minus-right difference ERPs optimally suited to accentuate left-lateralized language processes revealed an occipito-temporal processing negativity (210–270 ms) for all stimuli except alphanumerical strings. This asymmetry showed greater sensitivity to the combined effects of attention and lexicality than other ERPs in this time range (i.e., N170, P1, and P2). It is therefore introduced as “lexical asymmetry.”

The posterior semantic asymmetry (PSA): An early brain electrical signature of semantic activation from written words

This study replicates and extends the findings of Koppehele-Gossel, Schnuerch, and Gibbons (2016) of a posterior semantic asymmetry (PSA) in event-related brain potentials (ERPs), which closely tracks the time course and degree of semantic activation from single visual words. This negativity peaked 300 ms after word onset, was derived by subtracting right- from left-side activity, and was larger in a semantic task compared to two non-semantic control tasks. The validity of the PSA in reflecting the effort to activate word meaning was again attested by a negative correlation between the meaning-specific PSA increase and verbal intelligence, even after controlling for nonverbal intelligence. Extending prior work, current source density (CSD) transformation was used. CSD results were consistent with a left temporo-parietal cortical origin of the PSA. Moreover, no PSA was found for pictorial material, suggesting that the component reflects early semantic processing specific to verbal stimuli.

Affective priming and cognitive load: Event-related potentials suggest an interplay of implicit affect misattribution and strategic inhibition

Prior research suggests that the affective priming effect denoting prime-congruent evaluative judgments about neutral targets preceded by affective primes increases when the primes are processed less deeply. This has been taken as evidence for greater affect misattribution. However, no study so far has combined an experimental manipulation of the depth of prime processing with the benefits of ERPs. Forty-seven participants made like/dislike responses about Korean ideographs following 800-ms affective prime words while 64-channel EEG was recorded. In a randomized within-subject design, three levels of working-memory load were applied specifically during prime processing. Affective priming was significant for all loads and even tended to decrease over loads, although efficiency of the load manipulation was confirmed by reduced amplitudes of posterior attention-sensitive prime ERPs. Moreover, ERPs revealed greater explicit affective discrimination of the prime words as load increased, with strongest valence effects on central/centroparietal N400 and on the parietal/parietooccipital late positive complex under high load. This suggests that (a) participants by default tried to inhibit the processing of the prime's affect, and (b) inhibition more often failed under cognitive load, thus causing emotional breakthrough that resulted in a binding of affect to the prime and, hence, reduced affect misattribution to the target. As a correlate of affective priming in the target ERP, medial-frontal negativity, a well-established marker of (low) stimulus value, increased with increasing negative affect of the prime. Findings support implicit prime-target affect transfer as a major source of affective priming, but also point to the role of strategic top-down processes.

Motivated malleability: Frontal cortical asymmetry predicts the susceptibility to social influence

Humans, just as many other animals, regulate their behavior in terms of approaching stimuli associated with pleasure and avoiding stimuli linked to harm. A person's current and chronic motivational direction - that is, approach versus avoidance orientation - is reliably reflected in the asymmetry of frontal cortical low-frequency oscillations. Using resting electroencephalography (EEG), we show that frontal asymmetry is predictive of the tendency to yield to social influence: Stronger right- than left-side frontolateral activation during a resting-state session prior to the experiment was robustly associated with a stronger inclination to adopt a peer group's judgments during perceptual decision-making (Study 1). We posit that this reflects the role of a person's chronic avoidance orientation in socially adjusted behavior. This claim was strongly supported by additional survey investigations (Studies 2a, 2b, 2c), all of which consistently revealed that trait avoidance was positively linked to the susceptibility to social influence. The present contribution thus stresses the relevance of chronic avoidance orientation in social conformity, refining (yet not contradicting) the longstanding view that socially influenced behavior is motivated by approach-related goals. Moreover, our findings valuably underscore and extend our knowledge on the association between frontal cortical asymmetry and a variety of psychological variables.

A brain electrical signature of left-lateralized semantic activation from single words

Lesion and imaging studies consistently indicate a left-lateralization of semantic language processing in human temporo-parietal cortex. Surprisingly, electrocortical measures, which allow a direct assessment of brain activity and the tracking of cognitive functions with millisecond precision, have not yet been used to capture this hemispheric lateralization, at least with respect to posterior portions of this effect. Using event-related potentials, we employed a simple single-word reading paradigm to compare neural activity during three tasks requiring different degrees of semantic processing. As expected, we were able to derive a simple temporo-parietal left-right asymmetry index peaking around 300ms into word processing that neatly tracks the degree of semantic activation. The validity of this measure in specifically capturing verbal semantic activation was further supported by a significant relation to verbal intelligence. We thus posit that it represents a promising tool to monitor verbal semantic processing in the brain with little technological effort and in a minimal experimental setup.

Multiple neural signatures of social proof and deviance during the observation of other people's preferences

Detecting one's agreement with or deviation from other people, a key principle of social cognition, relies on neurocognitive mechanisms involved in reward processing, mismatch detection, and attentional orienting. Previous studies have focused on explicit depictions of the (in)congruency of individual and group judgments. Here, we report data from a novel experimental paradigm in which participants first rated a set of images and were later simply confronted with other individuals' ostensible preferences. Participants strongly aligned their judgments in the direction of other people's deviation from their own initial rating, which was neither an effect of regression toward the mean nor of evaluative conditioning (Experiment 1). Most importantly, we provide neurophysiological evidence of the involvement of fundamental cognitive functions related to social comparison (Experiment 2), even though our paradigm did not overly boost this process. Mismatches, as compared to matches, of preferences were associated with an amplitude increase of a broadly distributed N400-like deflection, suggesting that social deviance is represented in the human brain in a similar way as conflicts or breaches of expectation. Also, both early (P2) and late (LPC) signatures of attentional selection were significantly modulated by the social (mis)match of preferences. Our data thus strengthen and valuably extend previous findings on the neurocognitive principles of social proof.