Event-related Potential Effects Research Articles

Assessing the influence of latency variability on EEG classifiers - a case study of face repetition priming

AbstractData-driven strategies have been widely used to distinguish experimental effects on single-trial EEG signals. However, how latency variability, such as within-condition jitter or latency shifts between conditions, affects the performance of EEG classifiers has not been well investigated. Without explicitly considering and disentangling such attributes of single trials, neural network-based classifiers have limitations in measuring their contributions. Inspired by domain knowledge of subcomponent latency and amplitude from traditional cognitive neuroscience, this study applies a stepwise latency correction method on single trials to control for their contributions to classifier behavior. As a case study demonstrating the value of this method, we measure repetition priming effects of faces, which induce large reaction time differences, latency shifts, and amplitude effects in averaged event-related potentials. The results show that within-condition jitter negatively impacts classifier performance, but between-condition latency shifts improve accuracy, whereas genuine amplitude differences have no significant influence. While demonstrated in the case of priming effects, this methodology can be generalized to experiments involving many kinds of time-varying signals to account for the contributions of latency variability to classifier performance.

Threatening an Illusory Limb: An Event-related Potential Study of the Rubber Hand Illusion.

The rubber hand illusion (RHI) is a well-established method for studying body ownership: Given adequate concordance of visual, sensory, and proprioceptive stimuli, the individual experiences a rubber hand as his or her own. To study the effects of a threat to the rubber hand. We created a typical RHI paradigm but added threatening pain: Both the real hand of an individual and the rubber hand were stroked with a brush, either synchronously (RHI-inducing condition) or asynchronously (control condition), but only the rubber hand was then pricked with a needle to create a threatening pain condition. Event-related potentials (ERPs) were recorded in a group of 23 typically-developed individuals. ERP effects were source-localized using low-resolution electromagnetic tomography. The individuals consistently reported experience of the RHI during the experiment when the brush strokes were applied synchronously to both the real hand and the rubber hand. ERP analysis revealed that synchronous brush stroking gave rise to higher amplitude of frontal ERPs in the 100-200 ms range than asynchronous brush stroking, which was interpreted as reflecting the RHI. In the threatening pain condition, ERPs showed a greater positivity at frontocentral electrodes, source localized in the supplementary motor area (SMA). SMA activation could reflect a control mechanism over reflexive motor activity, facilitating a possible threat-related response. Further studies should address ERP effects and the extent of the RHI to standard and threat stimuli in a correlative fashion to further elucidate the functional significance of the neurophysiological findings.

Interaction of spatial attention and the associated reward value of audiovisual objects

Reward value and selective attention both enhance the representation of sensory stimuli at the earliest stages of processing. It is still debated whether and how reward-driven and attentional mechanisms interact to influence perception. Here we ask whether the interaction between reward value and selective attention depends on the sensory modality through which the reward information is conveyed. Human participants first learned the reward value of uni-modal visual and auditory stimuli during a conditioning phase. Subsequently, they performed a target detection task on bimodal stimuli containing a previously rewarded stimulus in one, both, or neither of the modalities. Additionally, participants were required to focus their attention on one side and only report targets on the attended side. Our results showed a strong modulation of visual and auditory event-related potentials (ERPs) by spatial attention. We found no main effect of reward value but importantly we found an interaction effect as the strength of attentional modulation of the ERPs was significantly affected by the reward value. When reward effects were examined separately with respect to each modality, auditory value-driven modulation of attention was found to dominate the ERP effects whereas visual reward value on its own led to no effect, likely due to its interference with the target processing. These results inspire a two-stage model where first the salience of a high reward stimulus is enhanced on a local priority map specific to each sensory modality, and at a second stage reward value and top-down attentional mechanisms are integrated across sensory modalities to affect perception.

Anterior N2 enhancement is not a general electrophysiological index of concealed information.

Event-related potentials (ERPs) have been used with the concealed information test (CIT) to detect concealed recognition of specific stimuli (i.e., "probes"). While most research has focused on the P300 component, which is larger for infrequent probes than for frequent control stimuli (i.e., "irrelevants"), some studies have investigated an earlier ERP component, the anterior N2, with mixed results. Although some studies have reported a larger anterior N2 for probes than irrelevants (N2 enhancement), other studies, including our own, have not found such an effect. The present study aimed to replicate and extend our previous findings using the same CIT paradigm and measurement parameters. Results of Bayesian analyses show strong evidence against the hypothesis of anterior N2 enhancement by probes, replicating our previous work. Bayesian analyses also show strong evidence against the hypothesis of N2 enhancement for the three components revealed by a temporal principal component analysis (PCA) conducted to disentangle potentially overlapping ERP effects. In conclusion, whereas the CIT has shown promise in detecting recognition of specific information, anterior N2 enhancement cannot be used as an electrophysiological measure of concealed information across CIT paradigms.

The impact of CSF-filled cavities on scalp EEG and its implications.

Previous studies have found electroencephalogram (EEG) amplitude and scalp topography differences between neurotypical and neurological/neurosurgical groups, being interpreted at the cognitive level. However, these comparisons are invariably accompanied by anatomical changes. Critical to EEG are the so-called volume currents, which are affected by the spatial distribution of the different tissues in the head. We investigated the effect of cerebrospinal fluid (CSF)-filled cavities on simulated EEG scalp data. We simulated EEG scalp potentials for known sources using different volume conduction models: a reference model (i.e., unlesioned brain) and models with realistic CSF-filled cavities gradually increasing in size. We used this approach for a single source close or far from the CSF-lesion cavity, and for a scenario with a distributed configuration of sources (i.e., a "cognitive event-related potential effect"). The magnitude and topography errors between the reference and lesion models were quantified. For the single-source simulation close to the lesion, the CSF-filled lesion modulated signal amplitude with more than 17% magnitude error and topography with more than 9% topographical error. Negligible modulation was found for the single source far from the lesion. For the multisource simulations of the cognitive effect, the CSF-filled lesion modulated signal amplitude with more than 6% magnitude error and topography with more than 16% topography error in a nonmonotonic fashion. In conclusion, the impact of a CSF-filled cavity cannot be neglected for scalp-level EEG data. Especially when group-level comparisons are made, any scalp-level attenuated, aberrant, or absent effects are difficult to interpret without considering the confounding effect of CSF.

How variable are the classic ERP effects during sentence processing? A systematic resampling analysis of the N400 and P600 effects

Although event-related potential (ERP) research on language processing has capitalized on key, theoretically influential components such as the N400 and P600, their measurement properties—especially the variability in their temporal and spatial parameters—have rarely been examined. The current study examined the measurement properties of the N400 and P600 effects elicited by semantic and syntactic anomalies, respectively, during sentence processing. We used a bootstrap resampling procedure to randomly draw many thousands of resamples varying in sample size and stimulus count from a larger sample of 187 participants and 40 stimulus sentences of each type per condition. Our resampling investigation focused on three issues: (a) statistical power; (b) variability in the magnitudes of the effects; and (c) variability in the temporal and spatial profiles of the effects. At the level of grand averages, the N400 and P600 effects were both robust and substantial. However, across resamples, there was a high degree of variability in effect magnitudes, onset times, and scalp distributions, which may be greater than is currently appreciated in the literature, especially for the P600 effects. These results provide a useful basis for designing future studies using these two well-established ERP components. At the same time, the results also highlight challenges that need to be addressed in future research (e.g., how best to analyze the ERP data without engaging in such questionable research practices as p-hacking).

Single-trial neurodynamics reveal N400 and P600 coupling in language comprehension

AbstractTheories of the electrophysiology of language comprehension are mostly informed by event-related potential effects observed between condition averages. We here argue that a dissociation between competing effect-level explanations of event-related potentials can be achieved by turning to predictions and analyses at the single-trial level. Specifically, we examine the single-trial dynamics in event-related potential data that exhibited a biphasic N400–P600 effect pattern. A group of multi-stream models can explain biphasic effects by positing that each individual trial should induce either an N400 increase or a P600 increase, but not both. An alternative, single-stream account, Retrieval-Integration theory, explicitly predicts that N400 amplitude and P600 amplitude should be correlated at the single-trial level. In order to investigate the single-trial dynamics of the N400 and the P600, we apply a regression-based technique in which we quantify the extent to which N400 amplitudes are predictive of the electroencephalogram in the P600 time window. Our findings suggest that, indeed, N400 amplitudes and P600 amplitudes are inversely correlated within-trial and, hence, the N400 effect and the P600 effect in biphasic data are driven by the same trials. Critically, we demonstrate that this finding also extends to data which exhibited only monophasic effects between conditions. In sum, the observation that the N400 is inversely correlated with the P600 on a by-trial basis supports a single stream view, such as Retrieval-Integration theory, and is difficult to reconcile with the processing mechanisms proposed by multi-stream models.

Asymetric Event-Related Potential Priming Effects Between English Letters and American Sign Language Fingerspelling Fonts.

Letter recognition plays an important role in reading and follows different phases of processing, from early visual feature detection to the access of abstract letter representations. Deaf ASL-English bilinguals experience orthography in two forms: English letters and fingerspelling. However, the neurobiological nature of fingerspelling representations, and the relationship between the two orthographies, remains unexplored. We examined the temporal dynamics of single English letter and ASL fingerspelling font processing in an unmasked priming paradigm with centrally presented targets for 200 ms preceded by 100 ms primes. Event-related brain potentials were recorded while participants performed a probe detection task. Experiment 1 examined English letter-to-letter priming in deaf signers and hearing non-signers. We found that English letter recognition is similar for deaf and hearing readers, extending previous findings with hearing readers to unmasked presentations. Experiment 2 examined priming effects between English letters and ASL fingerspelling fonts in deaf signers only. We found that fingerspelling fonts primed both fingerspelling fonts and English letters, but English letters did not prime fingerspelling fonts, indicating a priming asymmetry between letters and fingerspelling fonts. We also found an N400-like priming effect when the primes were fingerspelling fonts which might reflect strategic access to the lexical names of letters. The studies suggest that deaf ASL-English bilinguals process English letters and ASL fingerspelling differently and that the two systems may have distinct neural representations. However, the fact that fingerspelling fonts can prime English letters suggests that the two orthographies may share abstract representations to some extent.

An ERP measure of non-conscious memory reveals dissociable implicit processes in human recognition using an open-source automated analytic pipeline.

Non-conscious processing of human memory has traditionally been difficult to objectively measure and thus understand. A prior study on a group of hippocampal amnesia (N = 3) patients and healthy controls (N = 6) used a novel procedure for capturing neural correlates of implicit memory using event-related potentials (ERPs): old and new items were equated for varying levels of memory awareness, with ERP differences observed from 400 to 800 ms in bilateral parietal regions that were hippocampal-dependent. The current investigation sought to address the limitations of that study by increasing the sample of healthy subjects (N = 54), applying new controls for construct validity, and developing an improved, open-source tool for automated analysis of the procedure used for equating levels of memory awareness. Results faithfully reproduced prior ERP findings of parietal effects that a series of systematic control analyses validated were not contributed to nor contaminated by explicit memory. Implicit memory effects extended from 600 to 1000 ms, localized to right parietal sites. These ERP effects were found to be behaviorally relevant and specific in predicting implicit memory response times, and were topographically dissociable from other traditional ERP measures of implicit memory (miss vs. correct rejections) that instead occurred in left parietal regions. Results suggest first that equating for reported awareness of memory strength is a valid, powerful new method for revealing neural correlates of non-conscious human memory, and second, behavioral correlations suggest that these implicit effects reflect a pure form of priming, whereas misses represent fluency leading to the subjective experience of familiarity.

Successful reproduction of a large EEG study across software packages

As an active field of research and with the development of state-of-the-art algorithms to analyze EEG datasets, the parametrization of Electroencephalography (EEG) analysis workflows has become increasingly flexible and complex, with a great variety of methodological options and tools to be selected at each step. This high analytical flexibility can be problematic as it can yield to variability in research outcomes. Therefore, growing attention has been recently paid to understand the potential impact of different methodological decisions on the reproducibility of results.In this paper, we aim to examine how sensitive the results of EEG analyses are to variations in preprocessing with different software tools. We reanalyzed the shared EEG data (N = 500) from (Williams et al., 2021) using three of the most commonly used open-source Matlab-based EEG software tools: EEGLAB, Brainstorm and FieldTrip. After reproducing the same original preprocessing workflow in each software, the resulting event-related potentials (ERPs) were qualitatively and quantitatively compared in order to examine the degree of consistency/discrepancy between software packages. Our findings show a good degree of convergence in terms of the general profile of ERP waveforms, peak latencies and effect size estimates related to specific signal features. However, considerable variability was also observed in the magnitude of the absolute voltage observed with each software package as reflected by the similarity values and observed statistical differences at particular channels and time instants. In conclusion, we believe that this study provides valuable clues to better understand the impact of the software tool on the analysis of EEG results.

Beyond the N400: Confirmed and Disconfirmed Lexical Predictions in Aging

One of the basic tenets of predictive theories of language processing is that of misprediction cost. Post-N400 positive event-related potential (ERP) components are suitable for studying misprediction cost, but are not adequately described, especially in older adults, who show attenuated N400 ERP effects. We report a secondary analysis of a previously collected EEG data set. Using a picture–word matching paradigm, in which the target word could sometimes be predicted by context and sometimes not, the relationship between aging and late ERP effects was examined. Positivity effects for prediction violations were larger and more extended in older compared with younger adults, independent of context. Younger adults showed frontal negativity effects, indicating frame-shifting processes. Our data suggest that aging does not entail specific declines in prediction. Rather, they indicate that older adults may experience more processing difficulties than younger adults when their expectations are disconfirmed and that multiple mechanisms may be employed during language processing.

Perceptual learning of random acoustic patterns: Impact of temporal regularity and attention.

Perceptual learning is a powerful mechanism to enhance perceptual abilities and to form robust memory representations of previously unfamiliar sounds. Memory formation through repeated exposure takes place even for random and complex acoustic patterns devoid of semantic content. The current study sought to scrutinise how perceptual learning of random acoustic patterns is shaped by two potential modulators: temporal regularity of pattern repetition and listeners' attention. To this end, we adapted an established implicit learning paradigm and presented short acoustic sequences that could contain embedded repetitions of a certain sound segment (i.e., pattern) or not. During each experimental block, one repeating pattern recurred across multiple trials, whereas the other patterns were presented in only one trial. During the presentation of sound sequences that contained either temporally regular or jittered within-trial pattern repetitions, participants' attention was directed either towards or away from the auditory stimulation. Overall, we found a memory-related modulation of the event-related potential (ERP) and an increase in inter-trial phase coherence for patterns that recurred across multiple trials (compared to non-recurring patterns), accompanied by a performance increase in a (within-trial) repetition detection task when listeners attended the sounds. Remarkably, we show a memory-related ERP effect even for the first pattern occurrence per sequence when participants attended the sounds, but not when they were engaged in a visual distractor task. These findings suggest that learning of unfamiliar sound patterns is robust against temporal irregularity and inattention, but attention facilitates access to established memory representations upon first occurrence within a sequence.

Auditory pseudoword rhyming effects in bilingual children reflect second language proficiency: An ERP study

This study investigated second language (L2-English) phonological processing in 31 Spanish-English bilingual, 6- to 8-year-old schoolchildren in an event-related potential (ERP) auditory pseudoword rhyming paradigm. In addition, associations between ERP effects and L2 proficiency as measured by standardized tests of receptive language and receptive vocabulary were explored. We found a classic posterior ERP rhyming effect that was more widely distributed in children with higher L2 proficiency in group analyses and was larger for children with better L2 proficiency in correlation analyses. In contrast, the amplitude of an early (75–125 ms) auditory positivity was larger in children with lower L2 proficiency. This pattern suggests differential use of early and late auditory/phonological processing resources in the pseudoword rhyme task associated with L2 proficiency, which is consistent with the predictions of the lexical restructuring model in a bilingual context.

Perinatal nicotine exposure relates to stimulus-locked event-related potentials in early adolescence during an emotional go/no-go task

Nicotine exposure is associated with negative consequences on the developing brain, both in utero and after birth. We investigated the relationship between perinatal nicotine exposure and electroencephalographic brain activity recorded during an emotional faces Go/No-Go task among adolescents. Seventy-one adolescents aged 12–15 years completed a Go/No-Go task using fearful and happy faces. Parents completed questionnaire measures of their child's temperament and self-regulation and retrospectively reported on nicotine exposure during the perinatal period. Perinatally exposed children (n = 20) showed increased and prolonged frontal event-related potential (ERP) differentiation in stimulus-locked analyses; that is, greater emotion and condition differentiation in comparison with their non-exposed peers (n = 51). However, non-exposed children showed greater late emotion differentiation recorded over posterior sites. Response-locked ERP differences were not found. ERP effects were not related to temperamental, self-regulatory, or parental education and income-related factors. This study is the first to demonstrate a relationship between perinatal nicotine exposure and ERPs in an emotional Go/No-Go task among adolescents. Findings suggest that while conflict detection remains intact for adolescents with perinatal nicotine exposure, their attentional allocation to behaviourally relevant stimuli may be magnified to beyond optimal levels, particularly when emotion is salient in information processing. Future studies can extend these findings by isolating prenatal nicotine exposure and comparing its effects to isolated postnatal exposure and clarifying the implications of the face and performance processing differences in adolescence.

Sex-Determined Alteration of Frontal Electroencephalographic (EEG) Activity in Social Presence

This study represents a follow-up event-related potential (ERP) analysis of a prior investigation. The previous results showed that participants had most negative-tending ERPs in the mid-frontal brain region during exposure to neutral emotion pictures (compared to negative and positive pictures) while being accompanied by a significant other person (social presence condition). The present analysis aimed at investigating potential sex differences related to this phenomenon. Female and male participants' brain activity data from the previous study were analyzed separately for one representative mid-frontal electrode location selected on the basis of having the highest significance level. As a result, only female participants showed significantly more negative-tending potentials in response to neutral pictures, compared to both other emotion categories (positive and negative) in the social presence condition. This was not found in male participants. The respective ERP effect was most dominant at 838 ms post stimulus onset, which is slightly later than the effect found in the prior study. However, this result is interpreted as evidence that the general effect from the prior study can be understood as a largely female phenomenon. In line with the prior study, the present results are interpreted as a predominantly female activation in the mid-frontal brain region in response to neutral picture stimuli while being accompanied by a significant other person (social presence condition). Although only speculative, this would align with previous studies demonstrating sex-related hormonal and structural differences in the anterior cingulate cortex (ACC). In general, ACC activation has been associated with an integrative weighting function in ambiguous social settings, which makes sense given the ambiguous nature of neutral pictures in combination with a social presence condition.

Neural correlates of retrieval practice on the learning and memory retention of L3 French vocabulary

ABSTRACT This study used event-related potential (ERP) and retrieval practice effect paradigm to investigate the neurocognitive mechanisms underlying the retrieval practice effect in a third language (L3) vocabulary learning. Thirty-five Chinese (First Language, L1)-English (Second Language, L2) bilinguals without prior knowledge of French (L3) studied 120 French (L3)–English (L2) word pairs and then practiced the word pairs through retrieval practice or repeated studying. On a final recognition test 30 minutes later, the participants were asked to perform old/new recognition judgments while recording electroencephalography (EEG) signals. Behavioural results found that retrieval practice led to a higher accuracy rate and faster response time in the final test than repeated studying. ERP results found that retrieval practice elicited less negative N400 waveforms than repeated studying at the frontal site and less negative N400 waveforms than new condition at the central-parietal sites. By contrast, retrieval practice only elicited more positive LPC waveforms than new condition at the parietal site. In sum, the present results provide first neural evidence that retrieval practice facilitates L3 (French) vocabulary learning. These findings suggest that retrieval practice might involve more semantic information processing in L3 vocabulary learning, which supports the elaborative retrieval hypothesis of the retrieval practice effect.

Neurophysiological signatures of approximate number system acuity in preschoolers

BackgroundA hallmark of the approximate number system (ANS) is ratio dependence. Previous work identified specific event-related potentials (ERPs) that are modulated by numerical ratio throughout the lifespan. In adults, ERP ratio dependence was correlated with the precision of the numerical judgments with individuals who make more precise judgments showing larger ratio-dependent ERP effects. The current study evaluated if this relationship generalizes to preschoolers. MethodERPs were recorded from 56 4.5 to 5.5-year-olds while they compared the numerosity of two sequentially presented dot arrays. Nonverbal numerical precision, often called ANS acuity, was assessed using a similar behavioral task. ResultsOnly children with high ANS acuity exhibited a P2p ratio-dependent effect onsetting ∼250 ms after the presentation of the comparison dot array. Furthermore, P2p amplitude positively correlated with ANS acuity across tasks. ConclusionResults demonstrate developmental continuity between preschool years and adulthood in the neural basis of the ANS.

Task Demands Differentially Affect Processing of Intrinsic and Extrinsic Object Features in Working Memory

Some argue that visual working memory operates on integrated object representations. Here, we contend that obligatory feature integration occurs with intrinsic but not extrinsic object features. Working memory for shapes and colors was assessed using a change-detection task with a central test probe, while recording event-related potentials (ERPs). Color was either an intrinsic surface feature of a shape or connected to the shape via a proximal but spatially disjunct extrinsic frame. There were two types of test: The direct test required memory for shape and color; the indirect test required only shape memory. Study-test changes of color were therefore either task-relevant or task-irrelevant. We assessed performance costs and event-related potential (ERP) effects arising from color changes. In the direct test, performance was poorer for extrinsic than intrinsic stimuli; task-relevant color changes elicited enhanced frontal negativity (N2, FN400) for both intrinsic and extrinsic stimuli. In the indirect test, performance costs and ERP effects associated with irrelevant color change were larger for intrinsic than extrinsic stimuli. This suggests intrinsic information is more readily integrated into the working-memory representation and evaluated against the test probe. Findings imply that feature integration is not obligatory under all conditions but influenced by stimulus-driven and task-related focus of attention.

Behavioral and ERP effects of encoded facial expressions on facial identity recognition depend on recognized facial expressions.

Behavioral and event-related potential (ERP) studies have shown that the expressions of a face displayed in the encoding phase (encoded facial expressions) influences identity recognition of this face in a later recognition phase. As facial expressions displayed in the recognition phase (recognized facial expressions) might also influence facial identity recognition, the current study investigated whether the effect of encoded facial expressions on facial identity recognition changed depending on recognized facial expressions. Therefore, participants were asked to learn facial identities displaying angry, happy or neutral expressions during the encoding phase. In the subsequent recognition phase, participants were presented with the learned identities and several novel identities and asked to judge whether the prompted identities had been learned. Each identity displayed angry, happy and neutral expressions. The results showed that d' scores were smaller for happy-recognized identities (i.e., learned identities displaying happy expressions during the recognition phase) in the angry-encoded (i.e., learned identities that had displayed angry expressions during the preceding encoding phase) condition than in the neutral-encoded condition and for neutral-recognized identities in the angry-encoded condition than in the happy-encoded condition. ERP results showed that angry-encoded identities elicited less negative responses in the P200 and early posterior negativity (EPN)/N250 components and less positive responses in the late positive potential (LPP) component than happy-encoded identities. For neutral-recognized identities, LPP responses were reduced in the angry-encoded condition compared with those in the neutral-encoded condition. These findings might contribute to understanding the influence of previous and current facial expressions on facial identity recognition.

Longitudinal Effects of Breast Cancer Treatment on Neural Correlates of Attention.

Cognitive dysfunction has been observed consistently in a subset of breast cancer survivors. Yet, the precise physiological and processing origins of dysfunction remain unknown. The current study examined the utility of methods and procedures based on cognitive neuroscience to study cognitive change associated with cancer and cancer treatment. We used electroencephalogram and behavioral measures in a longitudinal design to investigate pre- versus post-treatment effects on attention performance in breast cancer patients (n = 15) compared with healthy controls (n = 24), as participants completed the revised Attention Network Test, a cognitive measure of alerting, orienting, and inhibitory control of attention. We found no group differences in behavioral performance from pretest to posttest, but significant event-related potential effects of cancer treatment in processing cue validity: After treatment, patients revealed decreased N1 amplitude and increased P3 amplitude, suggesting a suppressed early (N1) response and an exaggerated late (P3) response to invalid cues. The results suggest that treatment-related attentional disruption begins in early sensory/perceptual processing and extends to compensatory top-down executive processes.