Sex differences in two event-related potentials components related to semantic priming

The inter-related effects of alcohol use severity and sleep deficiency on semantic processing in young adults

BACKGROUND

Both alcohol misuse and sleep deficiency are associated with deficits in semantic processing. However, alcohol misuse and sleep deficiency are frequently comorbid and their inter-related effects on semantic processing as well as the underlying neural mechanisms remain to be investigated.

METHODS

We curated the Human Connectome Project data of 973 young adults (508 women) to examine the neural correlates of semantic processing in link with the severity of alcohol use and sleep deficiency. The latter were each evaluated using the first principal component (PC1) of principal component analysis of all drinking metrics and the Pittsburgh Sleep Quality Index (PSQI). We employed path modeling to elucidate the interplay among clinical, behavioral, and neural variables.

RESULTS

Among women, we observed a significant negative correlation between the left precentral gyrus (PCG) and PSQI scores. Mediation analysis revealed that the left PCG activity fully mediated the relationship between PSQI scores and word comprehension in language tasks. In women alone also, the right middle frontal gyrus (MFG) exhibited a significant negative correlation with PC1. The best path model illustrated the associations among PC1, PSQI scores, PCG activity, and MFG activation during semantic processing in women.

CONCLUSIONS

Alcohol misuse may lead to reduced MFG activation while sleep deficiency hinder semantic processing by suppressing PCG activity in women. The pathway model underscores the influence of sleep quality and alcohol consumption severity on semantic processing in women, suggesting that sex differences in these effects need to be further investigated.

Effect of Healthy Aging and Gender on Syntactic Input Processing: A P600 Event-Related Potential Study

PURPOSE

This study aimed to investigate the effect of healthy aging and gender, as well as the interaction, thereof, on syntactic input processing during sentence comprehension. This was achieved through the recording of the P600 event-related potential.

METHOD

Sixty Flemish (native speakers of Dutch) participants (30 men and 30 women), equally distributed into three age groups (young, middle-aged, and older adults), were subjected to a visually presented word order violation task under simultaneous electro-encephalography recording. The task contained 60 sentences, of which half were grammatical and half contained a word order violation. P600 responses were analyzed for amplitude, latency, topographical distribution, and source localization.

RESULTS

Regarding the effect of healthy aging, no age-related differences were found for the amplitude, onset latency, and topographical distribution of the P600 effect (difference wave). Although aging effects on the P600 effect amplitude were absent, a reduced P600 amplitude in response to both the grammatical and ungrammatical sentences was found, next to a reduced overall degree of source activation in linguistic regions of interest. Also, a reduced behavioral accuracy in response to the word order violation was observed in the older adults group. Regarding the effect of gender, females exhibited a larger P600 effect amplitude and a reduced behavioral accuracy compared to males. No gender-related differences were found for P600 effect onset latency, topographical distribution, and source activation.

CONCLUSIONS

While this study demonstrates no effect of aging on the P600 effect, the lower behavioral response and absence of any activation shift argues against functional compensation. Moreover, although increased neural activation in women combined with their reduced behavioral accuracy may indicate the use of different cognitive strategies in men and women, source localization analysis could not objectify this hypothesis.

Effects of Healthy Aging and Gender on the Electrophysiological Correlates of Semantic Sentence Comprehension: The Development of Dutch Normative Data

PURPOSE

The clinical use of event-related potentials in patients with language disorders is increasingly acknowledged. For this purpose, normative data should be available. Within this context, healthy aging and gender effects on the electrophysiological correlates of semantic sentence comprehension were investigated.

METHOD

One hundred and ten healthy subjects (55 men and 55 women), divided among three age groups (young, middle aged, and elderly), performed a semantic sentence congruity task in the visual modality during electroencephalographic recording.

RESULTS

The early visual complex was affected by increasing age as shown by smaller P2 amplitudes in the elderly compared to the young. Moreover, the N400 effect in the elderly was smaller than in the young and was delayed compared to latency measures in both middle-aged and young subjects. The topography of age-related amplitude changes of the N400 effect appeared to be gender specific. The late positive complex effect was increased at frontal electrode sites from middle age on, but this was not statistically significant. No gender effects were detected regarding the early P1, N1, and P2, or the late positive complex effect.

CONCLUSION

Especially aging effects were found during semantic sentence comprehension, and this from the level of perceptual processing on. Normative data are now available for clinical use.

Gender-dependent variations in optical illusions: evidence from N400 waveforms

OBJECTIVE

The cognitive mechanisms (especially the gender-related ones) underlying optical illusion processing remain elusive. Since the N400 component of event-related potentials (ERPs) is an index of the semantic integration of information processing tasks, the present study focuses on gender-related differences in N400 waveforms elicited during the reasoning process applied to reach a valid conclusion of optical illusions engaging working memory (WM).

APPROACH

Fifty-one healthy participants (28 males, age = 34.25 years ± 10.25, years of education = 16.00 years ± 1.78; and 23 females, age = 33.43 ± 7.93, years of education = 15.56 ± 1.82) were measured. The N400 ERP component was evoked by 39 optical illusions adjusted to induce WM. We compared brain activation patterns while participants maintained conclusions of the optical illusions in WM. The N400 of ERPs was recorded during the WM phase, during which participants were required to draw a logical conclusion regarding the correctness of the optical illusions.

MAIN RESULTS

Analysis revealed that females compared to males exhibited significantly increased N400 amplitudes located at parietal and occipital sites, whereas males exhibited significantly higher N400 amplitudes located at frontal areas. Furthermore, females compared to males demonstrated significantly prolonged latencies of the N400 component located at right frontotemporal abductions.

SIGNIFICANCE

These results suggest that coupling of optical illusions with WM engages distinct gender-related variations of brain semantic processing as reflected by the N400 ERP component. Based on the dual process account, our study gives support to the notion that women tend to employ a more deliberate and slower semantic reasoning than the men who tend to employ an automatic and fast one. Topographically, within the network sub-serving the semantic operation, the posterior brain areas responsible for sensorimotor integration-related processes elicit a greater brain activation among females while the anterior brain areas responsible for control and storage/retrieval operation elicit a greater brain activation among males.

The role of experience for abstract concepts: Expertise modulates the electrophysiological correlates of mathematical word processing

Embodied theories assign experience a crucial role in shaping conceptual representations. Supporting evidence comes mostly from studies on concrete concepts, where e.g., motor expertise facilitated action concept processing. This study examined experience-dependent effects on abstract concept processing. We asked participants with high and low mathematical expertise to perform a lexical decision task on mathematical and nonmathematical abstract words, while acquiring event-related potentials. Analyses revealed an interaction of expertise and word type on the amplitude of a fronto-central N400 and a centro-parietal late positive component (LPC). For mathematical words, we found a trend for a lower N400 and a significantly higher LPC amplitude in experts compared to nonexperts. No differences between groups were found for nonmathematical words. The results suggest that expertise affects the processing stages of semantic integration and memory retrieval specifically for expertise-related concepts. This study supports the generalization of experience-dependent conceptual processing mechanisms to the abstract domain.

The impact of spoken action words on performance in a cross-modal oddball task

In this study a cross-modal oddball task was employed to study the effect that words spoken either non-urgently or urgently would have on a digit categorization task and if women would exhibit greater behavioral inhibitory control. The words were unrelated to the task itself, but related to the action required to complete the task. Forty participants (21 women) conducted a computerized categorization task while exposed to a sinewave tone as a standard stimulus (75% of the trials) or a to-be ignored word (press, stop) spoken either non-urgently or urgently as unexpected auditory deviant stimulus (6.25% trials for each category). Urgent words had sharp intonation and an average fundamental frequency (F₀) ranging from 191.9 (stop) to 204.6 (press) Hz. Non-urgent words had low intonation with average F₀ ranging from 103.9.9 (stop) to 120.3 (press) Hz. As expected, deviant distraction and longer response times were found by exposure to the word stop, but deviant distraction was not found to be significant with the word press or due to intonation. While the results showed that women had in general longer reaction times, there were no gender differences found related to the deviant distraction caused by word or intonation. The present results do not support the hypothesis that women have greater behavioral inhibitory control, but there was evidence that the meaning of the word could influence response times.

The relationship between semantic access and introspective awareness

There have long been speculations about the relationship between consciousness and language. This study aimed to determine whether an individual's level of introspective awareness, based on self-report, relates to accessibility of their semantic system as evaluated by the N400. Thirty-five university students completed the study. All were right-handed, with normal or corrected-to-normal vision, without known neurological or psychological health issues. They first performed on a lexical decision task while their brain electrophysiological responses were recorded. Then, they provided assessment ratings about their levels of introspective awareness. Analysis revealed moderate to strong correlations (Pearson's rs = 0.49-0.62) between awareness self-ratings and ease of semantic access as indexed by the N400. Correlation between the self-report measure and the objective neurophysiological measure suggests that subjective assessment of awareness may deserve more credibility, which in addition to reflecting subjective perception and evaluation about one's own higher order mental functioning, may also interact with the neurophysiological processes contributive and subject to such awareness. Implications for future research on the role of semantic network in the mechanism of introspective awareness are discussed.

Tell me sweet little lies: An event-related potentials study on the processing of social lies

In reading tasks, words that convey a false statement elicit an enhanced N400 brainwave response, relative to words that convey a true statement. N400 amplitude reductions are generally linked to the online expectancy of upcoming words in discourse. White lies, contrary to false statements, may not be unexpected in social scenarios. We used the event-related potential (ERP) technique to determine whether there is an impact of social context on sentence processing. We measured ERP responses to target words that either conveyed a social "white" lie or a socially impolite blunt truth, relative to semantic violations. Word expectancy was controlled for by equating the cloze probabilities of white lying and blunt true targets, as measured in previous paper-and-pencil tests. We obtained a classic semantic violation effect (a larger N400 for semantic incongruities relative to sense making statements). White lies, in contrast to false statements, did not enhance the amplitude of the N400 component. Interestingly, blunt true statements yielded both a late frontal positivity and an N400 response in those scenarios particularly biased to white lying. Thus, white lies do not interfere with online semantic processing, and they do not engage further reanalysis processes, which are typically indexed by subsequent late positivity ERP effects. Instead, an N400 and a late frontal positivity obtained in response to blunt true statements indicate that they were treated as unexpected events. In conclusion, unwritten rules of social communicative behavior influence the electrical brain response to locally coherent but socially inappropriate statements.

Sex Differences in Neurophysiological Activation Patterns During Phonological Input Processing: An Influencing Factor for Normative Data

In the context of neurophysiological normative data, it has been established that aging has a significant impact on neurophysiological correlates of auditory phonological input processes, such as phoneme discrimination (PD) and word recognition (WR). Besides age, sex is another demographic factor that influences several language processes. We aimed to disentangle whether sex has a similar effect on PD and WR. Event-related potentials (ERPs) were recorded in 20 men and 24 women. During PD, three phonemic contrasts (place and manner of articulation and voicing) were compared using the attentive P300 and pre-attentive Mismatch Negativity. To investigate WR, real words were contrasted with pseudowords in a pre-attentive oddball task. Women demonstrated a larger sensitivity to spectrotemporal differences, as evidenced by larger P300 responses to the place of articulation (PoA) contrast and larger P300 and MMN responses than men in PoA-based PD. Men did not display such sensitivity. Attention played an important role, considering that women needed more attentional resources to differentiate between PoA and the other phonemic contrasts. During WR, pseudowords evoked larger amplitudes already 100 ms post-stimulus independent of sex. However, women had decreased P200 latencies, but longer N400 latencies in response to pseudowords, whereas men showed increased N400 latencies compared to women in response to real words. The current results demonstrate significant sex-related influences on phonological input processes. Therefore, existing neurophysiological normative data for age should be complemented for the factor sex.

The effects of gender and self-insight on early semantic processing

This event-related potential (ERP) study explored individual differences associated with gender and level of self-insight in early semantic processing. Forty-eight Chinese native speakers completed a semantic judgment task with three different categories of words: abstract neutral words (e.g., logic, effect), concrete neutral words (e.g., teapot, table), and emotion words (e.g., despair, guilt). They then assessed their levels of self-insight. Results showed that women engaged in greater processing than did men. Gender differences also manifested in the relationship between level of self-insight and word processing. For women, level of self-insight was associated with level of semantic activation for emotion words and abstract neutral words, but not for concrete neutral words. For men, level of self-insight was related to processing speed, particularly in response to abstract and concrete neutral words. These findings provide electrophysiological evidence for the effects of gender and self-insight on semantic processing and highlight the need to take into consideration subject variables in related research.

Effects of krill oil containing n-3 polyunsaturated fatty acids in phospholipid form on human brain function: a randomized controlled trial in healthy elderly volunteers

Background

Krill oil, rich in n-3 (omega-3) polyunsaturated fatty acids (PUFAs) incorporated in phosphatidylcholine, has been reported to have many effects on physiological function. However, there are few studies using psychophysiological methods published that describe the effects of krill oil on brain function. We investigated the influence of ingestion of krill oil on cognitive function in elderly subjects by using near-infrared spectroscopy and electroencephalography.

Methods

A randomized, double-blind, parallel-group comparative study design was adopted. Forty-five healthy elderly males aged 61–72 years were assigned to receive 12 weeks of treatment with: medium-chain triglycerides as placebo; krill oil, which is rich in n-3 PUFAs incorporated in phosphatidylcholine; or sardine oil, which is abundant in n-3 PUFAs incorporated in triglycerides. Changes in oxyhemoglobin concentrations in the cerebral cortex during memory and calculation tasks were measured. The P300 component of event-related potentials was also measured during a working memory task.

Results

During the working memory task, changes in oxyhemoglobin concentrations in the krill oil and sardine oil groups were significantly greater than those in the medium-chain triglyceride group at week 12. The differential value for P300 latency in the krill oil group was significantly lower than that in the medium-chain triglyceride group at week 12. With regard to the calculation task, changes in oxyhemoglobin concentrations in the krill oil group were significantly greater than those in the medium-chain triglyceride group at week 12.

Conclusion

This study provides evidence that n-3 PUFAs activate cognitive function in the elderly. This is especially the case with krill oil, in which the majority of n-3 PUFAs are incorporated into phosphatidylcholine, causing it to be more effective than sardine oil, in which n-3 PUFAs are present as triglycerides.

Gender differences on the semantic flanker task using transposed-letter target words

Previous research has demonstrated that men and women are differentially influenced by irrelevant distractors. Other lines of evidence have suggested that increasing the perceptual load of a task reduces distractor interference for participants generally. The present study examined these effects using a semantic version of the flanker task; participants made speeded responses to category target words that were flanked by irrelevant distractors. The response mapping between the target and flanker words was either congruent (mapped to the same motor response) or incongruent (target word mapped to a different motor response to that of the flankers). Target words were presented either normally (e.g., table: low perceptual load) or with the beginning letters transposed (e.g., atble: high perceptual load). The results revealed that women showed a larger congruency effect than men but this was not due to greater interference on incongruent trials. While men and women made faster responses to normal than to transposed target words, this was similar in magnitude. The magnitude of the flanker effect for normal and transposed target words was significantly correlated in men but not in women. These findings are consistent with the view that women may process target words to a deeper level than men and therefore may engage in more conflict monitoring then men.

Individual variation in the late positive complex to semantic anomalies

It is well-known that, within ERP paradigms of sentence processing, semantically anomalous words elicit N400 effects. Less clear, however, is what happens after the N400. In some cases N400 effects are followed by Late Positive Complexes (LPC), whereas in other cases such effects are lacking. We investigated several factors which could affect the LPC, such as contextual constraint, inter-individual variation, and working memory. Seventy-two participants read sentences containing a semantic manipulation (Whipped cream tastes sweet/anxious and creamy). Neither contextual constraint nor working memory correlated with the LPC. Inter-individual variation played a substantial role in the elicitation of the LPC with about half of the participants showing a negative response and the other half showing an LPC. This individual variation correlated with a syntactic ERP as well as an alternative semantic manipulation. In conclusion, our results show that inter-individual variation plays a large role in the elicitation of the LPC and this may account for the diversity in LPC findings in language research.

Neural correlates of foreign-language learning in childhood: a 3-year longitudinal ERP study

A foreign language (a language not spoken in one's community) is difficult to master completely. Early introduction of foreign-language (FL) education during childhood is becoming a standard in many countries. However, the neural process of child FL learning still remains largely unknown. We longitudinally followed 322 school-age children with diverse FL proficiency for three consecutive years, and acquired children's ERP responses to FL words that were semantically congruous or incongruous with the preceding picture context. As FL proficiency increased, various ERP components previously reported in mother-tongue (L1) acquisition (such as a broad negativity, an N400, and a late positive component) appeared sequentially, critically in an identical order to L1 acquisition. This finding was supported not only by cross-sectional analyses of children at different proficiency levels but also by longitudinal analyses of the same children over time. Our data are consistent with the hypothesis that FL learning in childhood reproduces identical developmental stages in an identical order to L1 acquisition, suggesting that the nature of the child's brain itself may determine the normal course of FL learning. Future research should test the generalizability of the results in other aspects of language such as syntax.

Empathy matters: ERP evidence for inter-individual differences in social language processing

When an adult claims he cannot sleep without his teddy bear, people tend to react surprised. Language interpretation is, thus, influenced by social context, such as who the speaker is. The present study reveals inter-individual differences in brain reactivity to social aspects of language. Whereas women showed brain reactivity when stereotype-based inferences about a speaker conflicted with the content of the message, men did not. This sex difference in social information processing can be explained by a specific cognitive trait, one's ability to empathize. Individuals who empathize to a greater degree revealed larger N400 effects (as well as a larger increase in γ-band power) to socially relevant information. These results indicate that individuals with high-empathizing skills are able to rapidly integrate information about the speaker with the content of the message, as they make use of voice-based inferences about the speaker to process language in a top-down manner. Alternatively, individuals with lower empathizing skills did not use information about social stereotypes in implicit sentence comprehension, but rather took a more bottom-up approach to the processing of these social pragmatic sentences.

Delayed auditory feedback effects during reading and conversation tasks: gender differences in fluent adults

Delayed auditory feedback (DAF) impacts the speech fluency of normally fluent males more than that of normally fluent females. Understanding this gender difference may contribute to our understanding of gender differences in the prevalence of developmental stuttering. To characterize this gender difference in fluent people, DAF-induced dysfluency was measured in 20 male and 21 female young adults during oral reading and conversation tasks. Stutter-like dysfluencies (SLDs), articulation errors, interjections, reading errors, and speech rate were measured for both speech tasks as the participant spoke without feedback, with non-delayed feedback, and with DAF presented with 5 delay intervals (14 conditions total). DAF induced SLDs (but not other dysfluencies) more frequently during conversation than reading, and this effect was significantly greater for males than females (Gender x Task x Feedback interaction). Males also produced significantly more reading errors than females. DAF reduced speaking rate significantly more while reading than conversing (Task x Feedback interaction). DAF significantly decreased the frequency of interjections and increased the frequency of articulation errors; however, no Gender effects on these variables were observed. Although significant order effects indicated improved fluency across trials, covariance analysis suggested that order effects could not explain other results.

EDUCATIONAL OBJECTIVES

After reading this article, the reader will be able to (1) Discuss developmental stuttering (DS) and gender differences in DS prevalence. (2) Define delayed auditory feedback (DAF). (3) Evaluate the evidence that gender is linked to DAF effects on fluent people. (4) Summarize the results of new research designed to assess sex differences in DAF effects on speech fluency in normally fluent adults. (5) Evaluate the degree to which evidence from the literature indicating that individual differences in attentional control may help us understand gender difference in DAF effects and possibly in DS prevalence as well.