Emotions in word and face processing: Early and late cortical responses

Capture of lexical but not visual resources by task-irrelevant emotional words: a combined ERP and steady-state visual evoked potential study

Numerous studies have found that emotionally arousing faces or scenes capture visual processing resources. Here we investigated whether emotional distractor words capture attention in an analogous way. Participants detected brief intervals of coherent motion in an array of otherwise randomly moving squares superimposed on words of positive, neutral or negative valence. Processing of the foreground task was assessed by behavioural responses and steady-state visual evoked potentials (SSVEPs) elicited by the squares flickering at 15 Hz. Although words were task-irrelevant, P2 and N400 deflections to negative words were enhanced, indicating that emotionally negative word content modulated lexico-semantic processing and that emotional significance was detected. In contrast, the time course of behavioural data and SSVEP amplitudes revealed no interference with the task regardless of the emotional connotation of distractor words. This dissociation of emotion effects on early perceptual versus lexical stages of processing suggests that written emotional words do not inevitably lead to attentional modulation in early visual areas. Prior studies have shown a distraction effect of emotional pictures on a similar task. Thus, our results indicate the specificity of emotion effects on sensory processing and semantic encoding dependent on the information channel that emotional significance is derived from.

The Time Course of Emotion Effects in First and Second Language Processing: A Cross Cultural ERP Study with German-Spanish Bilinguals

To investigate whether second language processing is characterized by the same sensitivity to the emotional content of language - as compared to native language processing - we conducted an EEG study manipulating word emotional valence in a visual lexical decision task. Two groups of late bilinguals - native speakers of German and Spanish with sufficient proficiency in their respective second language - performed each a German and a Spanish version of the task containing identical semantic material: translations of words in the two languages. In contrast to theoretical proposals assuming attenuated emotionality of second language processing, a highly similar pattern of results was obtained across L1 and L2 processing: event related potential waves generally reflected an early posterior negativity plus a late positive complex for words with positive or negative valence compared to neutral words regardless of the respective test language and its L1 or L2 status. These results suggest that the coupling between cognition and emotion does not qualitatively differ between L1 and L2 although latencies of respective effects differed about 50-100 ms. Only Spanish native speakers currently living in the L2 country showed no effects for negative as compared to neutral words presented in L2 - potentially reflecting a predominant positivity bias in second language processing when currently being exposed to a new culture.

Association with positive outcome induces early effects in event-related brain potentials

Emotional pictures, faces, or words elicit an early posterior negativity (EPN) in the event-related potential, starting around 200-400 ms, followed by a late positive complex (LPC). Occasionally, also very early effects of emotion (VEEEs) are seen prior to 200 ms. The present study examined whether VEEEs can be due to direct links established by reinforcement learning. In the learning session, participants learned to associate previously unknown Chinese words with monetary gain, loss, or neither. In the test session, they were required to distinguish the learned stimuli from novel distracters. Specific to stimuli associated with positive outcome a VEEE, consisting of a posterior positivity, appeared around 150 ms and an LPC between 550 and 700 ms, whereas an EPN was absent. These results show that previous association with reward can induce VEEEs, indicating that emotion effects in ERPs may arise in the absence of biologically preparedness and semantic meaning.

Are effects of emotion in single words non-lexical? Evidence from event-related brain potentials

Emotional meaning impacts word processing. However, it is unclear, at which functional locus this influence occurs and whether and how it depends on word class. These questions were addressed by recording event-related potentials (ERPs) in a lexical decision task with written adjectives, verbs, and nouns of positive, negative, and neutral emotional valence. In addition, word frequency (high vs. low) was manipulated. The early posterior negativity (EPN) in ERPs started earlier for emotional nouns and adjectives than for verbs. Depending on word class, EPN onsets coincided with or followed the lexicality effects. Main ERP effects of emotion overlapped with effects of word frequency between 300 and 550 ms but interacted with them only after 500 ms. These results indicate that in all three word classes examined, emotional evaluation as represented by the EPN has a post-lexical locus, starting already after a minimum of lexical access.

Emotional words impact the mind but not the body: evidence from pupillary responses

Pupillary responses have been shown to be sensitive to both task load and emotional content. We investigated the interplay of these factors in the processing of single words that varied in emotional valence and arousal. Two tasks of different cognitive load, uninstructed reading and a lexical decision task, were employed, followed by an unannounced recognition task. Reaction times were faster and incidental memory performance was better for high-arousing than for low-arousing words. In contrast to previous findings for pictures and sounds, high-arousing words elicited smaller pupillary responses than low-arousing words; these effects were independent of task load, which increased pupil diameter. Therefore, emotional arousal attributed to words does not mandatorily activate the autonomic nervous system, but rather works on a cognitive level, facilitating word processing.

Facial and semantic emotional interference: a pilot study on the behavioral and cortical responses to the Dual Valence Association Task

Background

Integration of compatible or incompatible emotional valence and semantic information is an essential aspect of complex social interactions. A modified version of the Implicit Association Test (IAT) called Dual Valence Association Task (DVAT) was designed in order to measure conflict resolution processing from compatibility/incompatibly of semantic and facial valence. The DVAT involves two emotional valence evaluative tasks which elicits two forms of emotional compatible/incompatible associations (facial and semantic).

Methods

Behavioural measures and Event Related Potentials were recorded while participants performed the DVAT.

Results

Behavioural data showed a robust effect that distinguished compatible/incompatible tasks. The effects of valence and contextual association (between facial and semantic stimuli) showed early discrimination in N170 of faces. The LPP component was modulated by the compatibility of the DVAT.

Conclusions

Results suggest that DVAT is a robust paradigm for studying the emotional interference effect in the processing of simultaneous information from semantic and facial stimuli.

Impact of emotion on consciousness: positive stimuli enhance conscious reportability

Emotion and reward have been proposed to be closely linked to conscious experience, but empirical data are lacking. The anterior cingulate cortex (ACC) plays a central role in the hedonic dimension of conscious experience; thus potentially a key region in interactions between emotion and consciousness. Here we tested the impact of emotion on conscious experience, and directly investigated the role of the ACC. We used a masked paradigm that measures conscious reportability in terms of subjective confidence and objective accuracy in identifying the briefly presented stimulus in a forced-choice test. By manipulating the emotional valence (positive, neutral, negative) and the presentation time (16 ms, 32 ms, 80 ms) we measured the impact of these variables on conscious and subliminal (i.e. below threshold) processing. First, we tested normal participants using face and word stimuli. Results showed that participants were more confident and accurate when consciously seeing happy versus sad/neutral faces and words. When stimuli were presented subliminally, we found no effect of emotion. To investigate the neural basis of this impact of emotion, we recorded local field potentials (LFPs) directly in the ACC in a chronic pain patient. Behavioural findings were replicated: the patient was more confident and accurate when (consciously) seeing happy versus sad faces, while no effect was seen in subliminal trials. Mirroring behavioural findings, we found significant differences in the LFPs after around 500 ms (lasting 30 ms) in conscious trials between happy and sad faces, while no effect was found in subliminal trials. We thus demonstrate a striking impact of emotion on conscious experience, with positive emotional stimuli enhancing conscious reportability. In line with previous studies, the data indicate a key role of the ACC, but goes beyond earlier work by providing the first direct evidence of interaction between emotion and conscious experience in the human ACC.

Emotional speech perception unfolding in time: the role of the basal ganglia

The basal ganglia (BG) have repeatedly been linked to emotional speech processing in studies involving patients with neurodegenerative and structural changes of the BG. However, the majority of previous studies did not consider that (i) emotional speech processing entails multiple processing steps, and the possibility that (ii) the BG may engage in one rather than the other of these processing steps. In the present study we investigate three different stages of emotional speech processing (emotional salience detection, meaning-related processing, and identification) in the same patient group to verify whether lesions to the BG affect these stages in a qualitatively different manner. Specifically, we explore early implicit emotional speech processing (probe verification) in an ERP experiment followed by an explicit behavioral emotional recognition task. In both experiments, participants listened to emotional sentences expressing one of four emotions (anger, fear, disgust, happiness) or neutral sentences. In line with previous evidence patients and healthy controls show differentiation of emotional and neutral sentences in the P200 component (emotional salience detection) and a following negative-going brain wave (meaning-related processing). However, the behavioral recognition (identification stage) of emotional sentences was impaired in BG patients, but not in healthy controls. The current data provide further support that the BG are involved in late, explicit rather than early emotional speech processing stages.

Early Neural Markers of Implicit Attitudes: N170 Modulated by Intergroup and Evaluative Contexts in IAT

The Implicit Association Test (IAT) is the most popular measure to evaluate implicit attitudes. Nevertheless, its neural correlates are not yet fully understood. We examined event related potentials (ERPs) in response to face- and word processing while indigenous and non-indigenous participants performed an IAT displaying faces (ingroup and outgroup members) and words (positive and negative valence) as targets of category judgments. The N170 component was modulated by valence of words and by ingroup/outgroup face categorization. Contextual effects (face–words implicitly associated in the task) had an influence on the N170 amplitude modulation. On the one hand, in face categorization, right N170 showed differences according to the association between social categories of faces and affective valence of words. On the other, in word categorization, left N170 presented a similar modulation when the task implied a negative-valence associated with ingroup faces. Only indigenous participants showed a significant IAT effect and N170 differences. Our results demonstrate an early ERP blending of stimuli processing with both intergroup and evaluative contexts, suggesting an integration of contextual information related to intergroup attitudes during the early stages of word and face processing. To our knowledge, this is the first report of early ERPs during an ethnicity IAT, opening a new branch of exchange between social neuroscience and social psychology of attitudes.

Emotion modulates language production during covert picture naming

Previous studies have shown that emotional content modulates the activity of several components of the event-related potentials during word comprehension. However, little is known about the impact of affective information on the different processing stages involved in word production. In the present study we aimed to investigate the influence of positive and negative emotions in phonological encoding, a process that have been shown to take place between 300 and 450 ms in previous studies. Participants performed letter searching in a picture naming task. It was found that grapheme monitoring in positive and negative picture names was associated with slower reaction times and enhanced amplitudes of a positive component around 400 ms as compared to monitoring letters in neutral picture names. We propose that this modulation reflects a disruption in phonological encoding processes as a consequence of the capture of attention by affective content. Grapheme monitoring in positive picture names also elicited higher amplitudes than letter searching in neutral image names in a positive component around 100 ms. This amplitude enhancement might be interpreted as a manifestation of the 'positive offset' during conceptual preparation processes. The results of a control experiment with a passive viewing task showed that both effects cannot be simply attributed to the processing of the emotional images per se. Overall, it seems that emotion modulates word production at several processing stages.

Looking at emotional words is not the same as reading emotional words: Behavioral and neural correlates

Recent research suggests that the allocation of attentional resources to emotional content during word processing might be sensitive to task requirements. This question was investigated in two tasks with similar instructions. The stimuli were positive, negative, and neutral nouns. Participants had to identify meaningful words embedded in a stream of non-recognizable stimuli (task 1) or pseudowords (task 2). Task 1 could be successfully performed on the basis of the perceptual features whereas a lexico-semantic analysis was required in task 2. Effects were found only in task 2. Positive nouns were identified faster, with fewer errors and elicited larger amplitude in an early negativity. Also, the amplitude of a late positivity was larger for both positive and negative nouns than for neutral nouns. It is concluded that some degree of linguistic processing is needed to direct attention to the affective content during word processing.