An ERP study of category priming: evidence of early lexical semantic access

We investigated the effects of lexical semantic access on early components of high-density ERPs. Participants performed five blocks of a standard lexical decision (LD) task in which visually presented words were distinguished from nonwords (pseudowords) matched on word length. A second condition involved a lexical semantic (LS) version, in which the words (e.g., tiger) used in each block were selected from a single category (e.g., animals). ERP results indicated that (1) a main effect of lexicality occurred at 100 ms with P1 amplitude greater for words than for nonwords; (2) a task effect for both words and nonwords was also found in the P1 amplitude (larger for LS); (3) a lexicalityxtask interaction in the N1 amplitude indicated lexical semantic access by 168 ms; (4) semantic facilitation of response time to word-nonword judgment may be largely explained by P1 enhancement. Our findings of an early lexicality effect at 100 ms and of semantic access by 168 ms is in accordance with results of recent ERP and eye movement studies.     

Emotion,Etmnooi, or Emitoon? – Faster lexical access to emotional than to neutral words during reading

Cortical processing of emotional words differs from that of neutral words. Using EEG event-related potentials (ERPs), the present study examines the functional stage(s) of this differentiation. Positive, negative, and neutral nouns were randomly mixed with pseudowords and letter strings derived from words within each valence and presented for reading while participants’ EEG was recorded. Results indicated emotion effects in the N1 (110–140 ms), early posterior negativity (EPN, 216–320) and late positive potential (LPP, 432–500 ms) time windows. Across valence, orthographic word-form effects occurred from about 180 ms after stimulus presentation. Crucially, in emotional words, lexicality effects (real words versus pseudowords) were identified from 216 ms, words being more negative over posterior cortex, coinciding with EPN effects, whereas neutral words differed from pseudowords only after 320 ms. Emotional content affects word processing at pre-lexical, lexical and post-lexical levels, but remarkably lexical access to emotional words is faster than access to neutral words.     

Inferring native language from early bio-electrical activity

Early semantic effects (<200 ms) for single word processing have been reported inconsistently, though not rarely, in the ERP literature. It may be hypothesized that the frequently reported later lexical effects are related to the lengthy processing of long/scarcely familiar words or task factors. In this paper, we have investigated the timing of brain activation during processing of native vs. later-acquired languages in simultaneous interpreters. The data show a clear-cut difference between native and foreign languages (proficiency being equal) in a silent letter detection task not requiring semantic processing. Although interpreters were equally proficient in L1 (Italian) and L2 (English), only L1 showed early lexical effects at occipito/temporal sites at about 160-180 ms. L2 words were distinguished from pseudo-words at about 260-320 ms (N2 level), while L3 (German) words showed a lexical effect only at about 320-380 ms (N3 level) at posterior sites. The fact that only L1 words were discriminated from pseudo-words at the earliest processing stage suggests a faster/more efficient access to lexicon for L1 than for later-acquired languages, regardless of proficiency.     

Emotion and attention in visual word processing: an ERP study

Emotional words are preferentially processed during silent reading. Here, we investigate to what extent different components of the visual evoked potential, namely the P1, N1, the early posterior negativity (EPN, around 250 ms after word onset) as well as the late positive complex (LPC, around 500 ms) respond differentially to emotional words and whether this response depends on the availability of attentional resources. Subjects viewed random sequences of pleasant, neutral and unpleasant adjectives and nouns. They were first instructed to simply read the words and then to count either adjectives or nouns. No consistent effects emerged for the P1 and N1. However, during both reading and counting the EPN was enhanced for emotionally arousing words (pleasant and unpleasant), regardless of whether the word belonged to a target or a non-target category. A task effect on the EPN was restricted to adjectives, but the effect did not interact with emotional content. The later centro-parietal LPC (450-650 ms) showed a large enhancement for the attended word class. A small and topographically distinct emotion-LPC effect was found specifically in response to pleasant words, both during silent reading and the active task. Thus, emotional word content is processed effortlessly and automatically and is not subject to interference from a primary grammatical decision task. The results are in line with other reports of early automatic semantic processing as reflected by posterior negativities in the ERP around 250 ms after word onset. Implications for models of emotion-attention interactions in the brain are discussed.     

Word frequency modulates the processing of emotional words: convergent behavioral and electrophysiological data

The processing of high frequency (HF) words is speeded as compared to the processing of low frequency (LF) words, which is known as the word frequency effect. This effect has been suggested to occur at either a lexical access or in a decision processing stage. Previous work has shown that word frequency influenced the processing of emotional content at both neural and behavioral levels. However, the results of these studies lead to discrepant findings because some of the variables that have shown to impact the processing of affective information were not always controlled. In order to make a better characterization of frequency effects on emotional word processing, event related potentials (ERPs) and reaction times to HF and LF negative and neutral nouns were measured as participants performed a lexical decision task. Temporal and spatial component analyses were used to detect and quantify, in a reliable way, those components associated with the interaction between word frequency and emotion. LF negative nouns were recognized faster and more accurately than LF neutral nouns whereas no differences were found in the HF word comparison. Also, LF neutral words elicited reduced amplitudes in a late positive component (P450) as compared to LF negative words. These findings might be reflecting a different involvement of attentional mechanisms during the evaluation of lexical information that benefits the processing of LF negative nouns.     

Emotionally positive stimuli facilitate lexical decisions-an ERP study

The influence of briefly presented positive and negative emotional pictures on lexical decisions on positive, negative and neutral words or pseudowords was investigated. Behavioural reactions were the fastest following all positive stimuli and most accurate for positive words. Stimulus-locked ERPs revealed enhanced early posterior and late parietal attention effects following positive pictures. A small neural affective priming effect was reflected by P3 modulation, indicating more attention allocation to affectively incongruent prime-target pairs. N400 was insensitive to emotion. Response-locked ERPs revealed an early fronto-central negativity from 480 ms before reactions to positive words. It was generated in both fronto-central and extra-striate visual areas, demonstrating a contribution of perceptual and, notably, motor preparation processes. Thus, no behavioural and little neural evidence for congruency-driven affective priming with emotional pictures was found, but positive stimuli generally facilitated lexical decisions, not only enhancing perception, but also acting rapidly on response preparation and by-passing full semantic analysis.     

Early semantic context integration and lexical access as revealed by event-related brain potentials

A late neurophysiological response, the N400, is well known to reflect word processing and semantic context integration. Nevertheless, behavioural and neurophysiological data have demonstrated that word features and semantic sentence context influence linguistic processes already within the first 200 ms following the onset of the critical word stimulus. The lack of early word-related ERP effects in some studies might be due to large stimulus variance on relevant linguistic parameters, for example the length of written words or their frequency of usage. Here we investigated the effect of the length of words, their standardized lexical frequency and probability to occur in a given semantic context, by orthogonally varying these factors in a sentence-reading task. We found word frequency and probability to be reflected neurophysiologically already at 120 and 180 ms after written word onset. However, at these early stages frequency and probability effects were modulated by word length, as documented by significant interactions, whereas at later stages, around 300-500 ms, additive effects of these variables were found. These results indicate that semantic context integration may take place at a surprisingly early stage and near-simultaneously with the processing of information about the form of a word and its lexical properties, therefore challenging serial models of psycholinguistic information access. A methodological implication of this study is that, in order to obtain early psycholinguistic ERP effects, stimulus variance must be kept to a minimum.     

The influence of stimulus valence on perceptual processing of facial expressions and subsequent response inhibition

The constant interplay between affective processing and cognitive control supports emotion regulation and appropriate social functioning. Even when affective stimuli are processed implicitly, threat-related stimuli are prioritized in the earliest stages of processing; yet, it remains unclear how implicit attention to affect influences subsequent cognitive control functions. The present study evaluated the influence of affective valence on early perceptual processes and subsequent response inhibition in a context where affective properties of the stimuli (facial expressions) were not critical for performing the task. Participants (N = 32) completed an affective stop-signal task (SST) while their scalp EEGs were recorded. The SST assessed response inhibition while participants implicitly attended to happy and afraid facial expressions that were matched for level of arousal. Behavioral performance was measured via response time and accuracy while physiological response was measured via the P100, N170, and N200/P300 ERP components. Decreased gender discrimination accuracy, delayed P100 latency, and more negative N170 amplitude were observed for afraid faces compared to happy faces, suggesting a shift in processing with respect to face valence. However, differences in stopping accuracy or N200/P300 ERP components during response inhibition were not observed, pointing to top-down cognitive processes likely being recruited to override the early automatic response to prioritize threat-related stimuli. Findings highlight that, in this implicit affective attention task, threat-related stimuli are prioritized early during processing, but implicitly attending to differentially valenced stimuli did not modulate subsequent cognitive control functions.     

Emotional conflict occurs at an early stage: Evidence from the emotional face–word Stroop task

The perceptual processing of emotional conflict was studied using electrophysiological techniques to measure event-related potentials (ERPs). The emotional face–word Stroop task in which emotion words are written in prominent red color across a face was use to study emotional conflict. In each trial, the emotion word and facial expression were either congruent or incongruent (in conflict). When subjects were asked to identify the expression of the face during a trial, the incongruent condition evoked a more negative N170 ERP component in posterior lateral sites than in the congruent condition. In contrast, when subjects were asked to identify the word during a trial, the incongruent condition evoked a less negative N170 component than the congruent condition. The present findings extend our understanding of the control processes involved in emotional conflict by demonstrating that differentiation of emotional congruency begins at an early perceptual processing stage.     

Phasic boosting of auditory perception by visual emotion

Emotionally negative stimuli boost perceptual processes. There is little known, however, about the timing of this modulation. The present study aims at elucidating the phasic effects of, emotional processing on auditory processing within subsequent time-windows of visual emotional, processing in humans. We recorded the electroencephalogram (EEG) while participants responded to a, discrimination task of faces with neutral or fearful expressions. A brief complex tone, which subjects, were instructed to ignore, was displayed concomitantly, but with different asynchronies respective to, the image onset. Analyses of the N1 auditory event-related potential (ERP) revealed enhanced brain, responses in presence of fearful faces. Importantly, this effect occurred at picture-tone asynchronies of, 100 and 150 ms, but not when these were displayed simultaneously, or at 50 ms or 200 ms asynchrony. These results confirm the existence of a fast-operating crossmodal effect of visual emotion on auditory, processing, suggesting a phasic variation according to the time-course of emotional processing.     

Attentional bias modulation by reappraisal in patients with generalized anxiety disorder: an event-related potential study

Affective states influence subsequent attention allocation. We evaluated emotional negativity bias modulation by reappraisal in patients with generalized anxiety disorder (GAD) relative to normal controls. Event-related potential (ERP) recordings were obtained, and changes in P200 and P300 amplitudes in response to negative or neutral words were noted after decreasing negative emotion or establishing a neutral condition. We found that in GAD patients only, the mean P200 amplitude after negative word presentation was much higher than after the presentation of neutral words. In normal controls, after downregulation of negative emotion, the mean P300 amplitude in response to negative words was much lower than after neutral words, and this was significant in both the left and right regions. In GAD patients, the negative bias remained prominent and was not affected by reappraisal at the early stage. Reappraisal was observed to have a lateralized effect at the late stage.     

Expectation decreases brain susceptibility to fearful stimuli: ERP evidence from a modified emotion evaluation task

Expectation decreased the susceptibility to fearful stimuli in prior studies using distracting tasks. The present study tests whether expectation remains effective in decreasing this susceptibility, when subjects focus attention on emotional properties. Event-related potentials were recorded for fearful and neutral faces, while subjects performed a modified emotion evaluation task during unpredictable and predictable conditions. Behavioral data showed faster response latencies during predictable versus unpredictable conditions. ERP data showed prolonged peak latencies in N1 (80–130 ms) and larger amplitudes in P2 (130–180 ms) and N200-300 components, for unpredictable fearful versus neutral faces. Conversely, all these components showed similar responses to predictable fearful and neutral faces. Source analysis suggested that medial temporal lobe mediated ERPs elicited by unpredictable fearful faces, while ventromedial prefrontal cortex mediated those elicited by predictable fearful faces, in the 130–180 ms interval. Thus, we propose emotional expectation as a cognitive regulation strategy that reliably dampens human susceptibility to fearful stimuli.     

An event-related potential study on cross-modal conversion of Chinese characters

In the current study, we explored the effects of ERPs (event-related potentials), related to the cross-modal transfer from visual input to phonological retrieval. Using Chinese single-character words, participants were asked to make orthographic (intra-modal) and phonological (cross-modal) responses to visually presented words. By comparing the cross-modal and intra-modal tasks, we found that both tasks evoke similar activity in the early stage of lexical processing, showing the same pattern of N2 effect (a negative component peaking around 220 ms) and P2 effect (a positive component peaking around 270 ms). However, the effect of the task was significant in the 300-700 ms time window, consisting of a frontal-based N400 effect and a parietal based late positive component (LPC) effect. These findings suggest that the frontal-based N400 is associated with orthography-to-phonology mapping in Chinese, and the LPC reflects greater requirement of maintaining retrieved information in working memory for the cross-modal processing.     

The role of encoding and attention in facial emotion memory: An EEG investigation

Facial expressions are encoded via sensory mechanisms, but meaning extraction and salience of these expressions involve cognitive functions. We investigated the time course of sensory encoding and subsequent maintenance in memory via EEG. Twenty-nine healthy participants completed a facial emotion delayed match-to-sample task. P100, N170 and N250 ERPs were measured in response to the first stimulus, and evoked theta power (4–7 Hz) was measured during the delay interval. Negative facial expressions produced larger N170 amplitudes and greater theta power early in the delay. N170 amplitude correlated with theta power, however larger N170 amplitude coupled with greater theta power only predicted behavioural performance for one emotion condition (very happy) out of six tested (see Supplemental Data). These findings indicate that the N170 ERP may be sensitive to emotional facial expressions when task demands require encoding and retention of this information. Furthermore, sustained theta activity may represent continued attentional processing that supports short-term memory, especially of negative facial stimuli. Further study is needed to investigate the potential influence of these measures, and their interaction, on behavioural performance.     

SOA-dependent N400 and P300 semantic priming effects using pseudoword primes and a delayed lexical decision.

In a previous semantic priming study, we found a semantic distance effect on the lexical-decision-related P300 when SOA was short (150 ms) only, but no different RT and N400 priming effects between short and long (700 ms) SOAs. To investigate this further, we separated priming from lexical decision, using a delayed lexical decision in the present study. In the short SOA only, primed targets evoked an early peaking (approximately 480 ms) P300-like component, probably because the subject detected the semantic relationship implicitly. We hypothesize that in tasks requiring an immediate lexical decision, this early P300 and the later lexical decision P300 (approximately 600 ms) are additive. Secondly, we found both a direct and an indirect priming effect for both SOAs for the ERP amplitude of the N400 time window. However the N400 component itself was considerably larger in the long SOA than in the short SOA. We interpreted this finding as an ERP correlate for deeper semantic processing in the long SOA, due to increased attention that was provoked by the use of pseudoword primes. In contrast, in the short SOA, subjects might have used a shallowed semantic processing. N400, P300, and RTs are sensitive to semantic priming-but the modulation patterns are not consistent. This raises the question as to which variable reflects an immediate physiological correlate of semantic priming, and which variable reflects co-occurring processes associated with semantic priming.     

Adult attachment and emotional processing biases: An Event-Related Potentials (ERPs) study

Attachment-related electrophysiological differences in emotional processing biases were examined using Event-Related Potentials (ERPs). We identified ERP correlates of emotional processing by comparing ERPs elicited in trials with angry and neutral faces. These emotional expression effects were then compared across groups with secure, anxious and avoidant attachment orientations. Results revealed significant interactions between attachment orientation and facial expression in mean amplitudes of the early C1 (50-80ms post-stimulus) and P1 (80-120ms post-stimulus) ERP components. Significant differences in C1 and P1 mean amplitudes were found at occipital and posterior-parietal channels in response to angry compared with neutral faces only within the avoidant attachment group. No such differences were found within the secure or anxious attachment groups. The present study underscores the usefulness of the ERP methodology, as a sensitive measure for the study of emotional processing biases in the research field of attachment.     

Electrophysiological correlates of decreasing and increasing emotional responses to unpleasant pictures

We examined event-related brain potential (ERP) modulations during the anticipation and processing of unpleasant pictures under instructions to cognitively decrease and increase negative emotion. Instructions to decrease and increase negative emotion modulated the ERP response to unpleasant pictures in the direction of emotional intensity beginning around 400 ms and lasting several seconds. Decrease, but not increase, instructions also elicited enhanced frontal negativity associated with orienting and preparation prior to unpleasant picture onset. Last, ERP modulation by unpleasant pictures began around 300 ms, just prior to regulation effects, suggesting that appraisal of emotion occurs before emotion regulation. Together, the current findings underscore the utility of ERPs in illuminating the time course of emotion modulation and regulation that may help to refine extant theoretical models.     

Time course of implicit processing and explicit processing of emotional faces and emotional words

Facial expressions are important emotional stimuli during social interactions. Symbolic emotional cues, such as affective words, also convey information regarding emotions that is relevant for social communication. Various studies have demonstrated fast decoding of emotions from words, as was shown for faces, whereas others report a rather delayed decoding of information about emotions from words. Here, we introduced an implicit (color naming) and explicit task (emotion judgment) with facial expressions and words, both containing information about emotions, to directly compare the time course of emotion processing using event-related potentials (ERP). The data show that only negative faces affected task performance, resulting in increased error rates compared to neutral faces. Presentation of emotional faces resulted in a modulation of the N170, the EPN and the LPP components and these modulations were found during both the explicit and implicit tasks. Emotional words only affected the EPN during the explicit task, but a task-independent effect on the LPP was revealed. Finally, emotional faces modulated source activity in the extrastriate cortex underlying the generation of the N170, EPN and LPP components. Emotional words led to a modulation of source activity corresponding to the EPN and LPP, but they also affected the N170 source on the right hemisphere. These data show that facial expressions affect earlier stages of emotion processing compared to emotional words, but the emotional value of words may have been detected at early stages of emotional processing in the visual cortex, as was indicated by the extrastriate source activity.     

An electrophysiological analysis of modality-specific aspects of word repetition.

Priming effects to words are reduced when modality changes from study to test. This change was examined here using behavioral and electrophysiological measures of priming. During the study, half of the words were presented visually and half auditorally; during a subsequent lexical decision test, all words were presented visually. Lexical decisions were faster for within- than cross-modality repetitions. In contrast, modality influenced recognition only for low-frequency words. During lexical decision, event-related brain potentials were more positive to studied than unstudied words (200-500 ms). A larger and shorter duration effect was observed for within- than cross-modality repetitions (300-400 ms). This later effect is viewed as an electrophysiological index of modality-specific processing associated with priming. Results suggest that multiple events--both modality-specific and modality-nonspecific--underlie perceptual priming phenomena.     

Electrophysiological indices of word fragment priming allow characterizing neural stages of speech recognition

Spoken word onset syllables (prime fragments) have been used to track neurophysiological processing of following written words (targets). Between 300 and 400 ms event-related potentials (ERPs) over the left hemisphere were more positive for targets that did not match their preceding prime fragments (e.g., hun-dragon) compared to matching targets (e.g., dra-dragon). This P350 effect has been related to the activation of modality independent neural word form representations. In the present experiment we set out to characterize neural word processing specific to the auditory domain. Spoken word onset syllables (prime fragments) were followed by spoken words (targets). Reduced amplitudes for matching targets were found for the N100 and the T-complex (100-300 ms), for the P350 (300-400 ms) and for a central negativity starting at 300 ms. The early potentials possibly index the priming of speech sound processing. The P350 replicates previous work with written words. This constitutes further evidence for shared neural word form representations in auditory and visual word recognition. The central negativity might be related to the rapid phonological matching of prime and target; or to the immediate testing of phonological expectations in speech recognition.