Event-related Brain Potentials Research Articles

Alpha-2 Adrenoreceptor Antagonist Yohimbine Potentiates Consolidation of Conditioned Fear.

BackgroundHyperconsolidation of aversive associations and poor extinction learning have been hypothesized to be crucial in the acquisition of pathological fear. Previous animal and human research points to the potential role of the catecholaminergic system, particularly noradrenaline and dopamine, in acquiring emotional memories. Here, we investigated in a between-participants design with 3 groups whether the noradrenergic alpha-2 adrenoreceptor antagonist yohimbine and the dopaminergic D2-receptor antagonist sulpiride modulate long-term fear conditioning and extinction in humans.MethodsFifty-five healthy male students were recruited. The final sample consisted of n = 51 participants who were explicitly aware of the contingencies between conditioned stimuli (CS) and unconditioned stimuli after fear acquisition. The participants were then randomly assigned to 1 of the 3 groups and received either yohimbine (10 mg, n = 17), sulpiride (200 mg, n = 16), or placebo (n = 18) between fear acquisition and extinction. Recall of conditioned (non-extinguished CS+ vs CS−) and extinguished fear (extinguished CS+ vs CS−) was assessed 1 day later, and a 64-channel electroencephalogram was recorded.ResultsThe yohimbine group showed increased salivary alpha-amylase activity, confirming a successful manipulation of central noradrenergic release. Elevated fear-conditioned bradycardia and larger differential amplitudes of the N170 and late positive potential components in the event-related brain potential indicated that yohimbine treatment (compared with a placebo and sulpiride) enhanced fear recall during day 2.ConclusionsThese results suggest that yohimbine potentiates cardiac and central electrophysiological signatures of fear memory consolidation. They thereby elucidate the key role of noradrenaline in strengthening the consolidation of conditioned fear associations, which may be a key mechanism in the etiology of fear-related disorders.

Event-related brain potentials study of arithmetic fact retrieval in children with different math achievement levels

ABSTRACT Fact retrieval deficits have been documented in children with mathematical learning disabilities. We assessed the retrieval of arithmetic facts in neurotypical 9-to-10-year-old children with different mathematical achievement levels using event-related potential methods while performing an arithmetic verification task (addition, subtraction, and multiplication). Forty-eight participants were divided into High (H), Average (A), and Low (L) mathematics performance according to their scores on The Wide Range Achievement Test 4 (WRAT4). Children determined whether appearing digits matched or not the correct solution of the preceding problem. L group showed a lower number of correct responses, prolonged reaction times, and poorer performance on working memory (WM) tasks. P300 component showed significantly higher amplitudes for correct solutions in H, while N270 showed higher amplitudes for incorrect solutions. L children showed difficulty in recovering arithmetic facts and poorly modulated N270 and P300 components, probably reflecting WM processing problems affecting the construction and retrieval of numerical information.

The effect of attention bias modification on the recognition of dynamic-angry faces in individuals with high social anxiety: Evidence from event-related brain potentials

The effect of attention bias modification on the recognition of dynamic-angry faces in individuals with high social anxiety: Evidence from event-related brain potentials

Emotion regulation and the late positive potential (LPP) in older adults

Emotion regulation (ER) processes in older adults may be important for successful aging. Neural correlates of ER processes have been examined using event-related brain potentials (ERPs), such as the late-positive potential (LPP) during cognitive reappraisal paradigms. The current study sought to extend this research by examining the LPP from an ER task in a sample of 47 community-dwelling older adults between the ages of 60 and 84 years, scoring either high on emotional well-being (as measured by habitual ER use and resiliency; high WB group, n = 20) or low on emotional well-being (as measured by habitual ER use, resiliency, and depression; low WB group, n = 27). Participants viewed unpleasant and neutral images and were instructed to simply react to the images or reappraise their emotional response. Both pre- and post-instruction LPP amplitudes were scored, in addition to self-reported ratings of negative emotion collected during the task. We found greater LPP amplitude to emotionally salient compared to neutral stimuli, reduced LPP amplitude following instructions to reappraise emotional response to stimuli across groups, and a blunted LPP overall for individuals with higher depressive symptoms. Additionally, we demonstrated that older adults with low emotional well-being were less successful at reappraisal according to self-reported ratings of negative emotion, although this was not reflected in the LPP. Collectively, these data suggest that laboratory-based ER tasks might be used to understand abnormal ER use—though the LPP may be more sensitive to depression than individual differences in ER ability.

Age-related Changes in Cortical Excitability Linked to Decreased Attentional and Inhibitory Control

Understanding age-related changes in cortical excitability and their relation to cognitive functions will help to improve interventions based on non-invasive brain stimulation that aim to support cognitive function in older adults. Here, we investigate the relationship between cortical excitability, executive function, and underlying neural activity in samples of healthy young and older adults. These participants performed a Simon task during electroencephalogram (EEG) recording. During the task, participants had to respond to the colour of a lateralized stimulus while ignoring its spatial location. We studied event-related brain potential correlates of attentional and inhibitory control [i.e., the posterior contralateral negativity (N2pc) and central contralateral negativity (N2cc), respectively] related to the Simon task performance. We also used transcranial magnetic stimulation (TMS) EEG coregistration. In detail, we applied single-pulse TMS during EEG recording in order to analyse global mean field power (GMFP) and TMS-evoked potentials (TEPs) as correlates of cortical excitability. We found lower GMFP amplitude within 101–200 ms in older compared to young adults. Moreover, older adults showed smaller N45 amplitude and slower P180 latency. These findings suggest cortical excitability alterations related to ageing. Older adults also exhibited longer reaction times and N2pc and N2cc latencies, indicating that it took them longer to allocate attention to the target stimulus and inhibit the tendency to respond to the attended location. Finally, in older adults, cortical excitability alterations correlated with longer reaction times and N2pc latencies. These results suggest that age-related alterations in cortical excitability represent a dysfunctional change associated with physiological ageing.

The Multi-Determined Nature of Online Verbal Irony Processing: A Review of Empirical Studies Employing Eye-Tracking and Event-Related Potentials

Methodologies used in behavioral studies on the processing of figurative languages have been criticized for lack of sufficiently fine-grained recordings. Thus, recent literature on empirical studies on irony processing often talks about advantages of online-processing employing techniques with higher temporal resolution. This article reviews a series of selected Event-Related Brain Potentials (ERPs) and eye-tracking studies on the recognition and comprehension of verbal irony to provide an informed state of knowledge on this particular figurative language. First of all, we will introduce some common eye-tacking measures and ERP components recorded in these empirical studies; then we will enumerate factors involved in verbal irony processing from three differing but closely related dimensions. In this way, we expect to propose future research directions that could embrace more cognitive difference of individuals within the framework of theories about verbal irony comprehension.

Investigation of the optimal time interval between task-irrelevant auditory probes for evaluating mental workload in the shortest possible time

Event-related brain potentials (ERPs) elicited by auditory stimuli unrelated to a current visual-cognitive task (i.e., task-irrelevant auditory probes) can be used to evaluate the level of mental workload. Towards the evaluation of workload in the shortest possible time, the present study with a multiple-stimulus paradigm (Takeda and Kimura, 2014, Int. J. Psychophysiol.) examined whether manipulating time intervals between probes could improve the temporal resolution in evaluating workload. Probes were presented in four interval conditions as a combination of two mean interval lengths [long (600 ms) vs. short (300 ms)] and two interval variabilities [variable (five levels) vs. fixed], while participants were performing a driving game at slow and fast speeds (i.e., imposing low and high workload, respectively). For each interval condition, the minimum data length required to obtain a significant difference in the amplitude of ERPs (i.e., auditory N1 and P2) between the slow and fast driving tasks was estimated. The N1 difference was significant in all four interval conditions but the required minimum data lengths to observe this difference did not greatly differ across the interval conditions (about 60–90 s). The P2 difference was significant only in the long-variable condition and the required minimum data length was about 120 s. These results suggest that, at least with a multiple-stimulus paradigm, manipulations of time intervals between probes did not greatly improve the temporal resolution in evaluating mental workload; at present, long-variable intervals would be optimal for evaluating mental workload in detail.

The P300, loneliness, and depression in older adults

Depression is associated with high levels of cognitive impairment and increased loneliness among older adults. The current study examines associations between a reliable and robust neural marker of cognitive impairment (i.e., the P300 event-related brain potential [ERP]), loneliness, and depression and assesses the role of loneliness in the P300─depression relationship. In a community sample of 70 older adults between 61 and 75 years, we evaluated cross-sectional associations between depressive symptoms (Geriatric Depression Scale), loneliness (NIH Toolbox), and P300 amplitude measured from the electroencephalogram during a go/no-go task. Results indicated that reduced go and no-go P300 amplitudes were associated with increased depressive symptom severity, with the most unique variance accounted for by a reduced no-go P300 amplitude. Notably, loneliness significantly moderated the no-go P300-depressive symptom severity relationship, such that there was no relationship between the no-go P300 and depressive symptom severity among older adults reporting low levels of loneliness. This finding provides insight into the possibility that social support may offer protection against the depressogenic effects of poor inhibitory control in older adults. Taken together, this study provides a novel examination of the relationships between depression, loneliness, and the P300 ERP in older adults, with important implications for understanding the role of neural inhibition and loneliness in relation to depressive symptomatology.

Association of prenatal exposure to dioxin-like compounds, polychlorinated biphenyl, and methylmercury with event-related brain potentials in school-aged children: The Hokkaido study

Previous studies have indicated that prenatal exposure to dioxin-like compounds (DLC) or polychlorinated biphenyl (PCB) has a negative association with neurodevelopment in school-aged children. Event-related brain potentials (ERP) can reveal subtle and specific differences in the modulation of cognitive processes that are assumed when they are associated with lower levels of prenatal exposure to DLC or PCBs. This prospective birth cohort study was conducted to examine the association between prenatal exposure to relatively low levels of DLC, PCB or methylmercury (MeHg), and ERP. A total of 55 children who were 13 years old participated in a 3-stimulus oddball task to detect P3a and P3b waves. The task required participants to respond to a target among random stimuli at two difficulty levels. The P3a amplitude reflects an automated attention capture process, and P3b reflects a voluntary attention allocation process. We analyzed DLC congeners in blood samples from four groups, including 7 polychlorinated dibenzo-p-dioxins (PCDD), 10 polychlorinated dibenzofuranes (PCDF), 4 non-ortho PCBs, and 8 mono-ortho PCBs. PCB-153 was chosen as an indicator because of its high correlation with the sum of 58 NDL (non-dioxin-like)-PCBs. MeHg exposure level was assessed by the mercury concentration in hair samples (HHg) taken during the perinatal period. The reaction time to the target stimulus during the oddball task shortened with the increasing MeHg exposure level. Furthermore, P3b latency, which reflect response decision and correlates with reaction time, was also shortened with increasing MeHg level in the difficult condition. These results are counterintuitive because shorter reaction times or rapid decision making reflected by P3 latency are generally favorable. This might be due to nutritional factors such as fatty acids, which have beneficial effects on brain development. The P3a amplitude decreased with non- and mono-ortho PCB and HHg levels, regardless of the difficulty level, and with PCDD, PCDF, and total DLC levels, especially in the difficult condition. P3b latency shortened with HHg, and P3b amplitude decreased with mono-ortho PCBs and PCB-153 in both conditions and with PCDD, PCDF, non-ortho PCBs, and total DLC in the difficult condition. In conclusion, we found an association between prenatal exposure to DLC and a decrease in both P3a and P3b amplitude, even when DLC levels were lower than in most previous studies. Additionally, our results suggest that the automated attention capture process reflected by P3a is associated with maternal MeHg exposure and that the voluntary attention allocation process reflected by P3b is associated with PCB-153. However, these results should be interpreted with caution because of the limitations on sample size, population bias, and statistical analyses.

The complexity of simple counting: ERP findings reveal early perceptual and late numerical processes in different arrangements

The counting process can only be fully understood when taking into account the visual characteristics of the sets counted. Comparing behavioral data as well as event-related brain potentials (ERPs) evoked by different task-irrelevant arrangements of dots during an exact enumeration task, we aimed to investigate the effect of illusory contour detection on the counting process while other grouping cues like proximity were controlled and dot sparsity did not provide a cue to the numerosity of sets. Adult participants (N = 37) enumerated dots (8–12) in irregular and two different types of regular arrangements which differed in the shape of their illusory dot lattices. Enumeration speed was affected by both arrangement and magnitude. The type of arrangement influenced an early ERP negativity peaking at about 270 ms after stimulus onset, whereas numerosity only affected later ERP components (> 300 ms). We also observed that without perceptual cues, magnitude was constructed at a later stage of cognitive processing. We suggest that chunking is a prerequisite for more fluent counting which influences automatic processing (< 300 ms) during enumeration. We conclude that the procedure of exact enumeration depends on the interaction of several perceptual and numerical processes that are influenced by magnitude and arrangement.

Mechanisms of associative word learning: Benefits from the visual modality and synchrony of labeled objects

Despite humans' ability to communicate about concepts relating to different senses, word learning research tends to largely focus on labeling visual objects. Although sensory modality is known to influence memory and learning, its specific role for word learning remains largely unclear. We investigated associative word learning in adults, that is the association of an object with its label, by means of event-related brain potentials (ERPs). We evaluated how learning is affected by object modality (auditory vs visual) and temporal synchrony of object-label presentations (sequential vs simultaneous). Across 4 experiments, adults were, in training phases, presented either visual objects (real-world images) or auditory objects (environmental sounds) in temporal synchrony with or followed by novel pseudowords (2 × 2 design). Objects and pseudowords were paired either in a consistent or an inconsistent manner. In subsequent testing phases, the consistent pairs were presented in matching or violated pairings. Here, behavioral and ERP responses should reveal whether consistent object–pseudoword pairs had been successfully associated with one another during training. The visual-object experiments yielded behavioral learning effects and an increased N400 amplitude for violated versus matched pairings indicating short-term retention of object–word associations, in both the simultaneous and sequential presentation conditions. For the auditory-object experiments, only the simultaneous, but not the sequential presentation, revealed similar results. Across all experiments, we found behavioral and ERP correlates of associative word learning to be affected by both sensory modality and partly, by temporal synchrony of object-label combinations. Based on our findings, we argue for independent advantages of temporal synchrony and visual modality in associative word learning.

Wrong or right? Brain potentials reveal hemispheric asymmetries to semantic relations during word-by-word sentence reading as a function of (fictional) knowledge

How does individual-level variation in experience and knowledge influence neural mechanisms important for real-time language comprehension? We used event-related brain potentials (ERPs) combined with lateralized visual field (VF) presentation of sentence-final words to examine asymmetries in hemispheric processing as individuals who varied in their knowledge of the fictional world of Harry Potter (HP) read sentences about general topics and HP. HP sentence endings were either contextually supported, unrelated anomalies, or semantically related anomalies. Amongst HP experts, we observed contextual support effects with presentation to both left and right VFs, but related anomaly effects only with presentation to the left VF (right hemisphere). Our findings are in line with accounts in which the left hemisphere (LH) activates relatively narrow/specific semantic information and the RH activates a broader range of semantic relations, including those relating to the construction of mental/situation models, as individuals attempt to comprehend sentences, one word at a time. We suggest that RH-biased hemispheric asymmetries in processing related (but linguistically inappropriate) words in written sentences may emerge as a function of each individual's degree of relevant knowledge. We tentatively hypothesize that content experts may optimize hemispheric differences in scope of semantic activation to maximize both precision (in the LH) and flexibility (in the RH) during language comprehension.

A N400 event-related potential elicitation paradigm for Canadian French speakers*

Abstract The N400 event-related brain potential (ERP) can be used to evaluate language comprehension, and may be a particularly powerful tool for the assessment of individuals who are behaviourally unresponsive. This study presents a set of semantic violation sentences developed in Canadian French and characterizes their ability to elicit an N400 effect in healthy adults. A novel set of 100 French sentences were created and normed through two surveys that assessed sentence cloze probability (n = 98) and semantic plausibility (n = 99). The best 80 sentences (40 congruent; 40 incongruent) were selected for the final stimulus set and tested for their ability to elicit N400 effects in 33 French-speaking individuals. The final stimulus set successfully generated an N400 effect in the grand-average across all individuals, and in the grand-average within age groups (young, middle-age, and older adults). On a single-subject level, the final stimulus set elicited N400 effects in 76% of the participants. The feasibility of using this stimulus set to assess semantic processing in behaviourally unresponsive individuals was demonstrated in a case example of a French individual in a disorder of consciousness. These sentences enable the inclusion of Canadian French speakers in this simple assessment of language comprehension abilities.

Belief in biological origin of race (racial essentialism) increases sensitivities to cultural category changes measured by ERP mismatch negativity (MMN)

The dynamic multicultural view explains culture-specific effects on cognition that cultural knowledge is organized in multiple knowledge systems which are specific to each culture and differentially activated when exposed to related objects or scenes. This view predicts automatic categorizations of environmental information according to the culture-specific knowledge systems. This study investigated whether cultural information could be spontaneously categorized, and the modulation of this process by the belief in the biological origin of race (i.e., racial essentialism) with an event-related brain potential, the visual Mismatch Negativity (vMMN). Deviant pictures of Eastern (Western) culture were randomly presented in a stream of standard Western (Eastern) pictures while participants were playing a video game. Participants who endorse racial essentialism (high group) showed vMMNs to the deviants with high relevance to the Eastern or Western culture and the deviant with low Eastern relevance; while participants with low racial essentialism showed vMMN to the deviant with high Eastern relevance only. These results revealed spontaneous cultural categorization with vMMN and the top-down modulation of spontaneous categorization by personal belief. In addition, this is the first demonstration of MMNs to cultural deviance and the potentials in applying MMNs to study psychological essentialism and social categorization.

The time it takes to truly know someone: Neurophysiological correlates of face and identity learning during the first two years

How long does it take to truly know a person? To answer this question, we investigated how event-related brain potential (ERP) correlates of facial familiarity (N250) and the integration of identity-specific knowledge (Sustained Familiarity Effect, SFE) develop over time. Sixty undergraduate students from three year groups were tested with images of a university friend (with two, 14, and 26 months of familiarity for Year 1, Year 2, and Year 3 students), a highly familiar friend from home, and an unfamiliar identity. While clear ERP familiarity effects for home friends were observed in all groups, university friends yielded a clear N250 effect but only a small SFE in Year 1. Importantly, both effects significantly increased for university friends from Year 1 to Year 2, but not afterwards. Our results demonstrate that neural representations of visual familiarity and identity-specific knowledge build up over time and are fully developed by 14 months of familiarity.

Meaning above (and in) the head: Combinatorial visual morphology from comics and emoji

Compositionality is a primary feature of language, but graphics can also create combinatorial meaning, like with items above faces (e.g., lightbulbs to mean inspiration). We posit that these “upfixes” (i.e., upwards affixes) involve a productive schema enabling both stored and novel face–upfix dyads. In two experiments, participants viewed either conventional (e.g., lightbulb) or unconventional (e.g., clover-leaves) upfixes with faces which either matched (e.g., lightbulb/smile) or mismatched (e.g., lightbulb/frown). In Experiment 1, matching dyads sponsored higher comprehensibility ratings and faster response times, modulated by conventionality. In Experiment 2, event-related brain potentials (ERPs) revealed conventional upfixes, regardless of matching, evoked larger N250s, indicating perceptual expertise, but mismatching and unconventional dyads elicited larger semantic processing costs (N400) than conventional-matching dyads. Yet mismatches evoked a late negativity, suggesting congruent novel dyads remained construable compared with violations. These results support that combinatorial graphics involve a constrained productive schema, similar to the lexicon of language.

Neurophysiological Basis of the Cognitive Gender Differences in Adulthood in Humans. Evidence from Event-related Brain Potentials

Gender can affect nervous system functioning at multiple levels – from genetics to behaviour. In the present review, effects of gender on neurophysiologic mechanisms of mental rotation, efficiency of language processing, emotions and sensory processes were studied in adults by exploring event-related brain potentials (ERPs). Since these processes were best recognized as gender-dependent at the behavioural level, it was aimed to verify the presence of gender effects on the respective ERP correlates at the neurophysiologic level. Articles from the PubMed database were selected, with a publication year until 2020. The review additionally includes studies that were cited in the selected articles. Thus, forty-six articles published between 1982 and 2020 were included. The reviewed data of healthy humans demonstrate that gender affects the early (related to perception and identification) and the late stages of processing (related to actual cognitive processes) of ERPs elicited during the three cognitive categories (mental rotation, language, and emotions). Mental rotation process in males demonstrates smaller amplitudes and shorter latencies of ERP components. It is concluded that men perform mental rotation more efficiently than females because they not only apply a different processing strategy (implied by distinct topography patterns), but they also benefit from faster processing mechanisms. During language processing, gender differences are expressed in increased amplitudes, shortened latencies, and different scalp topographies of language-related ERPs in females compared to males. ERPs confirm that the two genders employ different processing strategies and provide new evidence that females’ advantages can be associated with the fact that women are involved in a more extensive, more in-depth semantic processing and have a more automatized language processing. Gender differences in the emotion-related processes are mainly expressed as increased ERP amplitudes in females compared to males for both the early and late ERP components. ERP results reveal that women are more sensitive to emotionally salient stimuli, especially to unpleasant negative ones, and that this sensitivity extends beyond early emotional reactivity to a later emotional and emotion-regulation processes. However, studies exploring the neurophysiological level of the mental rotation process, language, and emotional processing in men and women are still scarce and inconsistent and thus further extensive research is required. The present review provides important hints that many of the established gender effects on specific processes (mental rotation, language and emotion regulation) may originate from fundamental and material-unspecific effects of gender on sensory processing mechanisms, which also merits additional clarification.

Encoding in a social feedback context enhances and biases behavioral and electrophysiological correlates of long-term recognition memory

Encoding often occurs in social contexts, yet research has hardly addressed their role in verbal memory. In three experiments, we investigated the behavioral and neural effects of encoding context on memory for positive, negative, and neutral adjectives, contrasting a social-feedback group (N = 24) with an explicit verbal-learning (N = 24) and a levels-of-processing group (N = 24). Participants in the social-feedback group were not aware of a recognition session one week later, but their memory was better than the explicit learning or the levels-of-processing groups'. However, they also exhibited the strongest response bias, particularly for positive words. Brain event-related potentials (ERPs) revealed largest early negativities (EPN) and late positivities (LPP) in the social-feedback group. Only in the subsequent slow-wave did the explicit learning group show higher amplitudes than the other two groups, suggesting reliance on strategic rather than automatic processes. Still, context-driven incidental encoding outweighed explicit instructions, specifying a decisive role of social factors in memory.

When multiplying is meaningful in memory: Electrophysiological signature of the problem size effect in children

Children are less fluent at verifying the answers to larger single-digit arithmetic problems compared with smaller ones. This problem size effect may reflect the structure of memory for arithmetic facts. In the current study, typically developing third to fifth graders judged the correctness of single-digit multiplication problems, presented as a sequence of three digits, that were either small (e.g., 4 3 12 vs. 4 3 16) or large (e.g., 8 7 56 vs. 8 7 64). We measured the N400, an index of access to semantic memory, along with accuracy and response time. The N400 was modulated by problem size only for correct solutions, with larger amplitude for large problems than for small problems. This suggests that only solutions that exist in memory (i.e., correct solutions) reflect a modulation of semantic access likely based on the relative frequency of encountering small versus large problems. The absence of an N400 problem size effect for incorrect solutions suggests that the behavioral problem size effects were not due to differences in initial access to memory but instead were due to a later stage of cognitive processing that was reflected in a post-N400 main effect of problem size. A second post-N400 main effect of correctness at occipital electrodes resembles the beginning of an adult-like brain response observed in prior studies. In sum, event-related brain potentials revealed different cognitive processes for correct and incorrect solutions. These results allude to a gradual transition to an adult-like brain response, from verifying multiplication problems using semantic memory to doing so using more automatic categorization.

DISCRIMINABILITY AND PROTOTYPICALITY OF NONNATIVE VOWELS

AbstractThis study examined how discriminability and prototypicality of nonnative phones modulate the amplitude of the Mismatch Negativity (MMN) event-related brain potential. We hypothesized that if a frequently occurring (standard) stimulus is not prototypical to a listener, a weaker predictive memory trace will be formed and a smaller MMN will be generated for a phonetic deviant, regardless of the discriminability between the standard and deviant stimuli. The MMN amplitudes of Japanese speakers hearing the English vowels /æ/ and /ɑ/ as standard stimuli and /ʌ/ as a deviant stimulus in an oddball paradigm were measured. Although the English /æ/-/ʌ/ contrast was more discriminable than the English /ɑ/-/ʌ/ contrast for Japanese speakers, when Japanese speakers heard the /æ/ standard stimulus (i.e., less prototypical as Japanese /a/) and the /ʌ/ deviant stimulus, their MMN amplitude was smaller than the one elicited when they heard /ɑ/ as a standard stimulus (i.e., more prototypical as Japanese /a/) and /ʌ/ as a deviant stimulus. The prototypicality of the standard stimuli in listeners’ phonological representations modulates the MMN amplitude more robustly than does the discriminability between standard and deviant stimuli.