Event-related potential correlates of emotional orthographic priming

Event-related potentials were used to explore the underlying mechanisms of masked orthographic priming and to determine whether the emotional valence of a word neighbor prime affects target processing in a lexical decision task. The results showed that the N200 and N400 amplitudes were modified by orthographic priming, which also varied with the emotional valence of the neighbors. These findings provide new evidence that the N400 component is sensitive to orthographic priming and further suggest that the affective content of the neighbor influences target word processing.     

Event-related brain potential correlates of emotional face processing

Results from recent event-related brain potential (ERP) studies investigating brain processes involved in the detection and analysis of emotional facial expression are reviewed. In all experiments, emotional faces were found to trigger an increased ERP positivity relative to neutral faces. The onset of this emotional expression effect was remarkably early, ranging from 120 to 180ms post-stimulus in different experiments where faces were either presented at fixation or laterally, and with or without non-face distractor stimuli. While broadly distributed positive deflections beyond 250ms post-stimulus have been found in previous studies for non-face stimuli, the early frontocentrally distributed phase of this emotional positivity is most likely face-specific. Similar emotional expression effects were found for six basic emotions, suggesting that these effects are not primarily generated within neural structures specialised for the automatic detection of specific emotions. Expression effects were eliminated when attention was directed away from the location of peripherally presented emotional faces, indicating that they are not linked to pre-attentive emotional processing. When foveal faces were unattended, expression effects were attenuated, but not completely eliminated. It is suggested that these ERP correlates of emotional face processing reflect activity within a neocortical system where representations of emotional content are generated in a task-dependent fashion for the adaptive intentional control of behaviour. Given the early onset of the emotion-specific effects reviewed here, it is likely that this system is activated in parallel with the ongoing evaluation of emotional content in the amygdala and related subcortical brain circuits.     

Electrophysiological correlates of the retrieval of emotional and non-emotional context

In two experiments, words were presented in negatively or neutrally valenced sentences. At test, subjects made old/new recognition judgments to these words. In Experiment 2 only, for words judged old, subjects also indicated whether the words had been studied in a neutral or a negative context. In Experiment 1, left parietal old/new event-related brain potential (ERP) effects were larger and more sustained when elicited by words that had been studied in negative sentences, and a right frontal old/new effect was elicited by these words exclusively. In Experiment 2, the left parietal and right frontal effects elicited by old words correctly assigned to their study context were equivalent in size regardless of the nature of the context; a third ERP old/new effect, maximal over posterior scalp regions, was seen only for words from negative contexts. The findings indicate that incidental retrieval of emotional context gives rise to greater activation in neural systems supporting conscious recollection than does retrieval of nonemotional context. When contextual retrieval is intentional, recollection of emotional and non-emotional information are associated with equivalent engagement of these systems. The findings from Experiment 2 suggest that additional neural circuitry may be activated selectively by emotionally valenced episodic information.     

Event-related potential correlates of the attentional blink phenomenon

The attentional blink phenomenon results from a transitory impairment of attention that can occur during rapid serial stimulus presentation. A previous study on the physiological correlates of the attentional blink employing event-related potentials (ERPs) suggested that the P3 ERP component for target items presented during this impairment is completely suppressed. This has been taken to indicate that the target-related information does not reach working memory. To reevaluate this hypothesis, we compared ERPs evoked by detected and missed targets in the attentional blink paradigm. Eighteen subjects performed a rapid serial visual presentation (RSVP) task in which either one target (control condition) or two targets had to be detected. ERPs elicited by the second target were analyzed separately for trials in which the target had been detected and missed, respectively. As predicted, detected targets did elicit a P3 during and after the attentional blink period. No clear P3 was found for detected targets presented before the attentional blink, that is, at lag 1. In contrast, missed targets generally did not evoke a P3. Our results provide evidence that targets presented during the attentional blink period can reach working memory. Thus, these findings contribute to evaluating theories of the attentional blink phenomenon.     

Event-related potential studies of associative recognition and recall: electrophysiological evidence for context dependent retrieval processes

To investigate the neural correlates of episodic recollection the ERP correlates of memory for new associations (recently studied novel word pairs) were investigated using two tasks, associative recognition and associative recall. For the recognition task subjects discriminated old from new word pairs and, for pairs judged old, reported whether the pairs were intact or recombined (compared to at study). For the recall task, subjects discriminated old from new words and, for each word judged old, reported its study associate. ERPs were recorded at test from 25 scalp electrodes, with a 1944-ms recording epoch. In Experiment 1, the tasks were randomly interleaved. Consistent with previous findings, relative to the ERPs for correctly classified new items, the ERP correlates of successful associative recognition consisted of a sustained left parietal positivity, and two frontal positivities, one early and bilateral, the other occurring later and showing a right-sided maximum. In contrast to previous findings, successful associative recall elicited similar effects to those found for recognition. Topographic analyses revealed that the distribution of these retrieval-related ERP effects were similar across the two tasks, suggesting that the recognition and recall of associative information gives rise to activity in overlapping, if not the same, neural populations. In Experiment 2 the tasks were blocked. In contrast to the findings of Experiment 1, successful associative recall elicited left parietal and late onsetting right frontal positivities, in the absence of the early bilateral frontal positivity. This finding suggests that frontally-distributed memory-related ERP effects are both neurally and functionally dissociable. Specifically, we argue that the functional significance of the early frontally distributed ERP effect cannot be accounted for by the 'post-retrieval processing' hypothesis that is taken to account for the late right frontal effect, suggesting that episodic recollection itself is neither neurally nor functionally homogenous.     

Event-related potential correlates of declarative and non-declarative sequence knowledge

The goal of the present study was to demonstrate that declarative and non-declarative knowledge acquired in an incidental sequence learning task contributes differentially to memory retrieval and leads to dissociable ERP signatures in a recognition memory task. For this purpose, participants performed a sequence learning task and were classified as verbalizers, partial verbalizers, or nonverbalizers according to their ability to verbally report the systematic response sequence. Thereafter, ERPs were recorded in a recognition memory task time-locked to sequence triplets that were either part of the previously learned sequence or not. Although all three groups executed old sequence triplets faster than new triplets in the recognition memory task, qualitatively distinct ERP patterns were found for participants with and without reportable knowledge. Verbalizers and, to a lesser extent, partial verbalizers showed an ERP correlate of recollection for parts of the incidentally learned sequence. In contrast, nonverbalizers showed a different ERP effect with a reverse polarity that might reflect priming. This indicates that an ensemble of qualitatively different processes is at work when declarative and non-declarative sequence knowledge is retrieved. By this, our findings favor a multiple-systems view postulating that explicit and implicit learning are supported by different and functionally independent systems.     

Event-related potential N270 correlates of brand extension

The aim of this study is to investigate the neural mechanism of extending a brand in a specific product category to other product categories. Facing two sequential stimuli in pairs consisting of beverage brand names (stimulus 1) and product names (stimulus 2) in other categories, 16 participants were asked to indicate the suitability of extending the brand in stimulus 1 to the product category in stimulus 2. These stimulus pairs were divided into four conditions depending on the product category in stimulus 2: beverage, snack, clothing, and household appliance. A negative component, N270, was recorded for each condition on the participants' scalps,whereas the maximum amplitude was observed at the frontal area. Greater N270 amplitude was observed when participants were presented with stronger conflict between the brand product category (stimulus 1) and the extension category (stimulus 2). It suggests that N270 can be evoked not only by a conflict of physical attributes (different shapes of words of brand and product names) but also by that of lexical content. From the marketing perspective, N270 can be potentially used as a reference measure in brand-extension attempts.     

Event-related potential correlates of paranormal ideation and unusual experiences

Separate dimensions of schizotypy have been differentially associated with electrophysiological measures of brain function, and further shown to be modified by sex/gender. We investigated event-related potential (ERP) correlates of two subdimensions of positive schizotypy, paranormal ideation (PI) and unusual experiences (UEs). Seventy-two individuals with no psychiatric diagnosis (men = 36) completed self-report measures of UE and PI and performed an auditory oddball task. Average scores for N100, N200 and P300 amplitudes were calculated for left and right anterior, central and posterior electrode sites. Multiple linear regression was used to examine the relationships between the measures of schizotypy and ERPs across the entire sample, as well as separately according to sex. PI was inversely associated with P300 amplitude at left-central sites across the entire sample, and at right-anterior electrodes in women only. Right-anterior P300 and right-posterior N100 amplitudes were negatively associated with UE in women only. Across the entire sample, UE was negatively associated with left-central N100 amplitude, and positively associated with left-anterior N200 amplitude. These results provide support from electrophysiological measures for the fractionation of the positive dimension of schizotypy into subdimensions of PI and UE, and lend indirect support to dimensional or quasidimensional conceptions of psychosis. More specifically, they suggest that PI may be associated with alteration in contextual updating processes, and that UE may reflect altered sensory/early-attention (N100) mechanisms. The sex differences observed are consistent with those previously observed in individuals with schizophrenia.     

Event-related potential correlates of inhibition in bipolar disorder

Lack of inhibitory control is a commonly reported impairment in patients with bipolar disorder, however, there has been little research regarding the time course of inhibitory processes. Twenty-six participants (13 bipolar and 13 controls) completed an emotional go/no-go inhibition task while event-related potentials were recorded. Go minus no-go difference waves were computed to index response inhibition. Across groups, there was greater activity in parietal and occipital compared with frontal and central electrodes. Longer latencies were found in bipolar disorder compared with controls. In conclusion, cortical regions recruited during response inhibition may be stimulus-dependent and not restricted to frontal areas. Impairments in bipolar disorder may relate to the speed at which inhibitory activity is executed, consistent with white matter deficits identified previously.     

Neurophysiological correlates of comprehending emotional meaning in context

Although the neurocognitive mechanisms of nonaffective language comprehension have been studied extensively, relatively less is known about how the emotional meaning of language is processed. In this study, electrophysiological responses to affectively positive, negative, and neutral words, presented within nonconstraining, neutral contexts, were evaluated under conditions of explicit evaluation of emotional content (Experiment 1) and passive reading (Experiment 2). In both experiments, a widely distributed Late Positivity was found to be larger to negative than to positive words (a "negativity bias"). In addition, in Experiment 2, a small, posterior N400 effect to negative and positive (relative to neutral) words was detected, with no differences found between N400 magnitudes to negative and positive words. Taken together, these results suggest that comprehending the emotional meaning of words following a neutral context requires an initial semantic analysis that is relatively more engaged for emotional than for nonemotional words, whereas a later, more extended, attention-modulated process distinguishes the specific emotional valence (positive vs. negative) of words. Thus, emotional processing networks within the brain appear to exert a continuous influence, evident at several stages, on the construction of the emotional meaning of language.     

Event-related potential correlates of impaired attention in schizophrenic children

Electrophysiological correlates of focused attention were studied in 13 schizophrenic and 19 age- and gender-matched children. Subjects performed a version of the Continuous Performance Task (CPT) in which a target was designated as any digit from 0 through 9 occurring on two successive stimulus presentations. Signal digits were surrounded by distractor digits which varied in position, value, and number. Event-related potentials (ERPs) elicited by each stimulus of a target pair were recorded from midline and homologous parietal, temporal, and occipital electrode placements. Schizophrenic children made significantly more errors of omission and commission than normal children. The amplitude and time course of the intertrial CNV was the same for both groups. There was a circumscribed amplitude asymmetry, left smaller than right, for the P1/N1 and P2 measures which was greater in normal than in schizophrenic children. The P3 component was significantly larger to the second stimulus of the target pair than to the first for both groups, and larger for the normal than the schizophrenic children to both stimuli.     

Event-related potential P2 correlates of implicit aesthetic experience

Using event-related potential measures, the present study investigated the affective responses to aesthetic experience. To differentiate the objective aesthetic value from subjective aesthetic evaluation, an amended oddball task was used in which pendant pictures were presented as frequent nontarget stimuli, whereas the landscape pictures were presented as a rare target. The pendant pictures were chosen from the largest online store in China and divided into beautiful and less beautiful conditions by the sales ranking. A positive component, P2, was recorded for each condition on the participants' frontal, central and parietal scalp areas. Less beautiful pendants elicited greater amplitudes of P2 than the beautiful ones. This indicates that emotion arousal seems to occur at the early stage of processing of aesthetics and can be detected by the P2 component, implying that the event-related potential methodology may be a more sensitive measure of the beauty-related attention bias. From the perspective of artwork design and marketing, our finding also shows that P2 can potentially be used as a reference measure in consumer aesthetic experience.     

Event-related potential correlates of repetition priming for ignored faces

An attentional capacity limit was recently suggested for faces, such that only one face can be processed at a time. We measured interference and repetition priming caused by irrelevant distractor faces. Participants initially performed male/female judgments for central faces or symbols flanked by distractor faces. Interference (slower responses for sex-incongruent target-distractor pairs) occurred for central symbols but was absent for central faces. In subsequent fame judgements, previously presented distractor faces had no repetition priming effect on response times. Relative to new faces, event-related brain potentials revealed a right occipitotemporal negativity approximately 400-600 ms for faces previously shown as distractors flanking central symbols (but not distractors flanking faces). These findings support a face-specific attentional capacity limit, showing that event-related brain potential priming effects can reveal covert distractor processing.     

Event-related potential correlates selectively reflect cognitive dysfunction in schizophrenics

Summary. Schizophrenics show event-related potential (ERP) and particularly P3 abnormalities. To study the more detailed relationships between these ERP alterations and cognitive dysfunction we recorded and analyzed ERPs using a particular experimental approach. In 34 schizophrenics and 25 controls ERPs were obtained by a visual Go/Nogo task requiring response inhibition and were decomposed into temporally independent topographical components using Independent Component Analysis (ICA). ICA disentangled different subcomponents of P3. Subcomponent P3b with a parietal maximum amplitude was significantly reduced in the schizophrenics, probably reflecting their attentional deficits. Subcomponent P3ng with a frontal maximum amplitude and enhanced during Nogo condition appeared as an electrophysiological index of response inhibition. A significantly reduced P3ng enhancement, found in schizophrenics, probably reflects their impaired response control. Conclusions: ICA can successfully identify ERP subcomponents with distinct scalp topographies representing significant differential indices of normal and abnormal cognitive processing. Involvement of frontal brain areas in disturbed executive control in schizophrenics is supported by our ICA findings.     

Event-related potential correlates of language change detection in bilingual toddlers

Children raised in a bilingual environment are faced with the daunting task of learning to extract meaning from language input that can differ between caregivers but, depending on the social context, also within caregivers. Here, we investigated monolingual and bilingual toddlers' brain responses to an unexpected language change. We presented 2-3 year old children with picture-word pairs and occasionally changed the language of the spoken word while recording event-related potentials (ERPs). In line with previous results obtained in adults, bilingual children differentiated between the languages of input faster than their monolingual peers, i.e., within 200 ms of spoken word onset, a time range previously associated with lexical access. However, while adult bilinguals displayed a late stimulus re-evaluation ERP response to a language change, no such modulation was found in bilingual toddlers. These results suggest that although bilingual individuals are sensitive to phonemic language cues already from an early age, language awareness and language monitoring mechanisms probably develop later in life.     

Event-related potential correlates of long-term memory for briefly presented faces

Electrophysiological studies have investigated the nature of face recognition in a variety of paradigms; some have contrasted famous and novel faces in explicit memory paradigms, others have repeated faces to examine implicit memory/priming. If the general finding that implicit memory can last for up to several months also holds for novel faces, a reliable measure of it could have practical application for eyewitness testimony, given that explicit measures of eyewitness memory have at times proven fallible. The current study aimed to determine whether indirect behavioral and electrophysiological measures might yield reliable estimates of face memory over longer intervals than have typically been obtained with priming manipulations. Participants were shown 192 faces and then tested for recognition at four test delays ranging from immediately up to 1 week later. Three event-related brain potential components (e.g., N250r, N400f, and LPC) varied with memory measures although only the N250r varied regardless of explicit recognition, that is, with both repetition and recognition.     

Event-related potential correlates of negation in a sentence-picture verification paradigm

In a sentence-picture verification paradigm, participants were presented in a rapid-serial-visual-presentation paradigm with affirmative or negative sentences (e.g., "In the front of the tower there is a/no ghost") followed by a matching or mismatching picture. Response latencies and event-related potentials (ERPs) were measured during reading and verification. An enhanced negative shift in the ERPs for the subject noun (i.e., "ghost") in negative, compared to affirmative sentences, was found during reading. We relate this ERP deflection to enhanced processing demands required by the negative particle no. Although this effect suggests a direct impact of negation on language processing, results for picture processing reveal that negation is not immediately integrated into sentence meaning. When the delay of picture presentation was short (250 msec), verification latencies and ERPs evoked by the picture showed a priming effect independent of whether the sentence contained a negation. Unprimed pictures (foreground object not mentioned in the sentence) led to longer latencies and higher N400 amplitudes than primed pictures (foreground object mentioned in the sentence). Main effects of negation showed up only in a late positive-going ERP effect. In contrast, when the delay was long (1500 msec), we observed main effects of truth value and negation in addition to the priming effect already in the N400 time window, that is, negation is fully integrated into sentence meaning only at a later point in the comprehension process. When negation has not yet been integrated, verification decisions appear to be modulated by additional time-consuming reanalysis processes.     

Event-related potential signatures of perceived and imagined emotional and food real-life photos

Although food and affective pictures share similar emotional and motivational characteristics, the relationship between the neuronal responses to these stimuli is unclear. Particularly, it is not known whether perceiving and imagining food and affective stimuli elicit similar event-related potential(ERP) patterns. In this study, two ERP correlates,the early posterior negativity(EPN) and the late positive potential(LPP) for perceived and imagined emotional and food photographs were investigated.Thirteen healthy volunteers were exposed to a set of food photos, as well as unpleasant, pleasant,and neutral photos from the International Affective Picture System. In each trial, participants were first asked to view a photo(perception condition), and then to create a visual mental image of it and to rate its vividness(imagery condition). The results showed that during perception, brain regions corresponding to sensorimotor and parietal motivational(defensive and appetitive) systems were activated to different extents, producing a graded pattern of EPN and LPP responses specifi c to the photo content – more prominent for unpleasant than pleasant and food content. Also, an EPN signature occurred in both conditions for unpleasant content, suggesting that,compared to food or pleasant content, unpleasant content may be attended to more intensely duringperception and may be represented more distinctly during imagery. Finally, compared to LLP activation during perception, as well as imagery and perception of all other content, LPP activation was signifi cantly reduced during imagery of unpleasant photos, suggesting inhibition of unwanted memories. Results are framed within a neurocognitive working model of embodied emotions.     

Event-related potential variations in the encoding and retrieval of different amounts of contextual information

Episodic memory events occur within multidimensional contexts; however, the electrophysiological manifestations associated with processing of more than one context have been rarely investigated. The effect of the amount of context on the ERPs was studied using two single and one double source memory tasks and by comparing full and partial context retrieval within a double source task. The single source tasks elicited waveforms with a larger amplitude during successful encoding and retrieval than the double source task. Compared with the waveforms elicited with a full source response, a partial source response elicited waveforms with a smaller amplitude, probably because the retrieval success for one context was combined with the retrieval attempt processes for the missing source. Comparing the tasks revealed that the larger the amount of contextual information processed, the smaller the amplitude of the ERPs, indicating that greater effort or further control processes were required during double source retrieval.     

Event-related potential correlates of the serial position effect in short-term memory.

Event-related potential (ERP) correlates of the serial position effect in short-term memory were investigated using a memory scanning task. Nine normal young adults (18-39 years) indicated whether a probe item was a member of a previously presented 5-item memory set by pressing 1 of 2 reaction-time buttons. Three types of stimuli were used: verbal digits presented both auditorily and visually, and musical notes presented auditorily. The ERPs to the probes were separately averaged according to the serial position of the probe (1, 2, 3, 4 or 5) in the memory set. The ERPs to the memory set items in positions 1, 3 and 5 also were separately averaged. Both baseline-to-peak and average amplitudes of a late positive parietal potential to the probes were larger to probe items presented in the last position in the memory set than to probes presented in the middle positions (2, 3 and 4), showing a significant recency effect, but only for auditory digits. Reaction time reflected significant recency effects for both auditory digits and notes, but not for visual digits. Response accuracy (percent correct) showed a significant recency effect only for notes. For each stimulus type, both the baseline-to-peak and average amplitudes of a late frontal component to the memory set items became more negative (in the case of the visual digits, less positive) in the third and last serial position of the memory set compared to the first. These findings provide electrophysiological evidence of serial position effects in short-term memory, which, during memory scanning, are dependent on stimulus modality (auditory, visual) and type (verbal, non-verbal).