Delayed cortical processing of auditory stimuli in children with autism spectrum disorder: A meta-analysis of electrophysiological studies.

Several researchers have hypothesised that individuals with Autism Spectrum Disorder (ASD) show encoding delays in their obligatory event-related potentials (ERPs)/ event-related fields (ERFs) for low-level auditory information compared to neurotypical (NT) samples. However, empirical research has yielded varied findings, such as low-level auditory processing in ASD samples being unimpaired, superior, or impaired compared to NT samples. Diverse outcomes have also been reported for studies investigating ASD-NT differences in functional lateralisation of delays. The lack of consistency across studies has prevented a comprehensive understanding of the overall effects in the autistic population. Therefore, this meta-analysis compared long-latency ERPs and ERFs produced by autistic and NT individuals to non-linguistic auditory stimuli to test, firstly, the robustness of auditory processing differences and, secondly, whether these differences are observed in one or both hemispheres. Nine articles meeting the inclusion criteria were included in the meta-analysis. Meta-analytic results indicated that autistic individuals demonstrate bilaterally delayed P1/ M50 peaks and lateralised delays in the right but not left hemisphere N1/ M100 peak. These results further inform our understanding of auditory processing and lateralisation across the autism spectrum.

Impaired practice effects following mild traumatic brain injury: an event-related potential investigation.

BACKGROUND: The negative effects of mild traumatic brain injury (mTBI) on attention are well established. Effects of practice on neuropsychological test performance have also been long recognized and more recently linked to electrophysiological indices of information processing. OBJECTIVE: The current study examined the behavioural and electrophysiological impact of mTBI on consistent practice of a neuropsychological test of attention. RESEARCH DESIGN: Prospective cohort study. METHODS: Adult participants with a history of mild TBI (n = 10; time since injury > 2 months, mean = 15.2 months) and healthy matched controls (n = 10) completed the Paced Auditory Serial Addition Task (PASAT) at four separate sessions. Event-related potentials (ERPs) were simultaneously recorded. RESULTS: Accuracy of PASAT performance in both groups improved significantly with practice. In healthy controls behavioural improvements were associated with significant attenuation of a frontally distributed ERP component marker of executive attention. These executive attention demands did not appear to ease with consistent practice in the mTBI group, who also endorsed more concussion-related symptoms. CONCLUSIONS: These preliminary results suggest sustained mental effort is required to achieve 'normal' performance levels following mTBI and support the use of practice-related, ERP indices of recovery from mTBI as a sensitive correlate of persistent post-concussion symptoms.

Global shape processing: A behavioral and electrophysiological analysis of both contour and texture processing.

The number of corners on the boundary of a closed contour is thought to be particularly critical for shape detection and discrimination. The aim of the current study was to examine the relative contribution of the number of corners and the angle between corners to shape discrimination in complex visual scenes as well as to determine the time course and neural substrates of global shape processing based on the presence or absence of these specific features. In Experiment 1, event-related potentials were recorded while participants discriminated between two radial frequency (RF) patterns with the same maximum local curvature defining corners but varying arrangements of those corners. The results showed that the angle separating corners was more critical than the overall number of corners for discrimination performance. An enhanced negativity (posterior N220) over the occipital lobe was elicited following the presentation of an RF with three modulation cycles (RF3) but not following a circle, suggesting that the posterior N220 is sensitive to variation in curvature on a contour. In Experiment 2, we confirm the primary effect of the presence of corners on the amplitude of the posterior N220 component and extend the stimuli to include shapes defined by texture. Source localization on the N170 and N220 components was conducted in Experiment 2, and a source in cortical area V4 was identified. These findings suggest that corners contain vital information for the discrimination of shapes. Additionally, this study shows that the perceptual characteristics and neuroanatomical substrates can be detected using electrophysiological measures.

Maturation of rapid auditory temporal processing and subsequent nonword repetition performance in children.

According to the rapid auditory processing theory, the ability to parse incoming auditory information underpins learning of oral and written language. There is wide variation in this low-level perceptual ability, which appears to follow a protracted developmental course. We studied the development of rapid auditory processing using event-related potentials (ERPs) elicited by tone pairs presented at varying inter-stimulus intervals (25, 50, 100, 200, and 400 ms) in a sample of children (N = 103) aged 7-9 years initially and again at 9-11 years. We also assessed their ability to repeat nonsense words at both time-points. The amount of difference between the ERP to single tones and paired tones (as assessed by the intra-class correlation coefficient, ICC) provided a measure of the brain's capacity to discriminate auditory information delivered at different presentation rates. Results showed that older children showed greater neural discrimination to tone pairs than younger children at rapid presentation rates, although these differences were reduced at slower presentation rates. The ICC at time 1 significantly predicted nonword repetition scores two years later, providing support for the view that rapid auditory temporal processing ability affects oral language development in typically developing children.

Vitamin B-12 and the Gastrointestinal Microbiome: A Systematic Review.

Vitamin B-12 deficiency is a major public health problem affecting individuals across the lifespan, with known hematological, neurological, and obstetric consequences. Emerging evidence suggests that vitamin B-12 may have an important role in other aspects of human health, including the composition and function of the gastrointestinal (gut) microbiome. Vitamin B-12 is synthesized and utilized by bacteria in the human gut microbiome and is required for over a dozen enzymes in bacteria, compared to only 2 in humans. However, the impact of vitamin B-12 on the gut microbiome has not been established. This systematic review was conducted to examine the evidence that links vitamin B-12 and the gut microbiome. A structured search strategy was used to identify in vitro, animal, and human studies that assessed vitamin B-12 status, dietary intake, or supplementation, and the gut microbiome using culture-independent techniques. A total of 22 studies (3 in vitro, 8 animal, 11 human observational studies) were included. Nineteen studies reported that vitamin B-12 intake, status, or supplementation was associated with gut microbiome outcomes, including beta-diversity, alpha-diversity, relative abundance of bacteria, functional capacity, or short-chain fatty acids (SCFA) production. Evidence suggests that vitamin B-12 may be associated with changes in bacterial abundance. While results from in vitro studies suggest that vitamin B-12 may increase alpha-diversity and shift gut microbiome composition (beta-diversity), findings from animal studies and observational human studies were heterogeneous. Based on evidence from in vitro and animal studies, microbiome outcomes may differ by cobalamin form and co-intervention. To date, few prospective observational studies and no randomized trials have been conducted to examine the effects of vitamin B-12 on the human gut microbiome. The impact of vitamin B-12 on the gut microbiome needs to be elucidated to inform screening and public health interventions.

Neural indicators of error processing and intraindividual variability in reaction time in 7 and 9 year-olds.

Childhood is associated with improvements in task accuracy, response time, and reductions in intraindividual trial-to-trial variability in reaction times. The aims of this study were to investigate neural indicators of error monitoring to better understand the mechanisms underlying these cognitive developments in primary school aged children. Specifically, this study explored the development of error processing in 36 children aged 7 years and 41 children aged 9 years, as indexed by two electrophysiological indices of error processing, the error-related negativity (ERN) and the error positivity (Pe). Notably, the amplitude and latency of the ERN and Pe did not differ significantly between the age groups. However, intraindividual variability in response time (RT) was strongly related to ERN amplitude. These data suggest the utility of comparing neural and behavioral indicators of cognitive performance in children and uniquely highlight the importance of considering intraindividual variability in task performance in studies that explore error processing.

Processing emotional category congruency between emotional facial expressions and emotional words.

Facial expressions are critical for effective social communication, and as such may be processed by the visual system even when it might be advantageous to ignore them. Previous research has shown that categorising emotional words was impaired when faces of a conflicting valence were simultaneously presented. In the present study, we examined whether emotional word categorisation would also be impaired when faces of the same (negative) valence but different emotional category (either angry, sad or fearful) were simultaneously presented. Behavioural results provided evidence for involuntary processing of basic emotional facial expression category, with slower word categorisation when the face and word categories were incongruent (e.g., angry word and sad face) than congruent (e.g., angry word and angry face). Event-related potentials (ERPs) time-locked to the presentation of the word-face pairs also revealed that emotional category congruency effects were evident from approximately 170 ms after stimulus onset.

Maturation of auditory temporal integration and inhibition assessed with event-related potentials (ERPs).

BACKGROUND: We examined development of auditory temporal integration and inhibition by assessing electrophysiological responses to tone pairs separated by interstimulus intervals (ISIs) of 25, 50, 100, 200, 400, and 800 ms in 28 children aged 7 to 9 years, and 15 adults. RESULTS: In adults a distinct neural response was elicited to tones presented at ISIs of 25 ms or longer, whereas in children this was only seen in response to tones presented at ISIs above 100 ms. In adults, late N1 amplitude was larger for the second tone of the tone pair when separated by ISIs as short as 100 ms, consistent with the perceptual integration of successive stimuli within the temporal window of integration. In contrast, children showed enhanced negativity only when tone pairs were separated by ISIs of 200 ms. In children, the amplitude of the P1 component was attenuated at ISIs below 200 ms, consistent with a refractory process. CONCLUSIONS: These results indicate that adults integrate sequential auditory information into smaller temporal segments than children. These results suggest that there are marked maturational changes from childhood to adulthood in the perceptual processes underpinning the grouping of incoming auditory sensory information, and that electrophysiological measures provide a sensitive, non-invasive method allowing further examination of these changes.

Differential effects of ecstasy on short-term and working memory: a meta-analysis.

Quantitative analysis of studies examining the effect of ecstasy on short-term and working memory in the verbal and visuo-spatial domain was undertaken. Thirty verbal short-term memory, 22 verbal working memory, 12 visuospatial short-term memory and 9 visuospatial working memory studies met inclusion criteria. Ecstasy users performed significantly worse in all memory domains, both in studies using drug-naïve controls and studies using polydrug controls. These results are consistent with previous meta-analytic findings that ecstasy use is associated with impaired short-term memory function. Lifetime ecstasy consumption predicted effect size in working memory but not in short-term memory. The current meta-analysis adds to the literature by showing that ecstasy use in humans is also associated with impaired working memory, and that this impairment is related to total lifetime ecstasy consumption. These findings highlight the long-term, cumulative behavioral consequences associated with ecstasy use in humans.

Fast fronto-parietal cortical dynamics of conflict detection and context updating in a flanker task.

Recent research has found that the traditional target P3 consists of a family of P3-like positivities that can be functionally and topographically dissociated from one another. The current study examined target N2 and P3-like subcomponents indexing conflict detection and context updating at low- and high-order levels in the neural hierarchy during cognitive control. Electroencephalographic signals were recorded from 45 young adults while they completed a hybrid go/nogo flanker task, and Residue Iteration Decomposition (RIDE) was applied to functionally dissociate these peaks. Analyses showed a stimulus-locked frontal N2 revealing early detection and fast perceptual categorization of nogo, congruent and incongruent trials, resulting in frontal P3-like activity elicited by nogo trials in the latency-variable RIDE cluster, and by incongruent trials in the response-locked cluster. The congruent trials did not elicit frontal P3-like activity. These findings suggest that behavioral incongruency effects are related to intermediate and later stages of motor response re-programming.

The relationship between naturalistic sleep variation and error monitoring in young adults: An event-related potential (ERP) study.

Sleep deprivation studies have highlighted the importance of adequate sleep for optimal daytime functioning. However, there is limited research exploring whether variations in natural sleep patterns produce similar difficulties to those seen in sleep deprivation studies. The aim of the current study was to explore whether naturalistic reductions in sleep duration and/or sleep quality were associated with behavioural and electrophysiological measures of cognitive control. Sixty undergraduate students were asked to wear an actigraph for 7 consecutive nights before completing a hybrid Flanker-Go/NoGo task whilst continuous EEG data were recorded. Participants were assigned to high or low sleep quality and short or long sleep duration groups using the National Sleep Foundation guidelines. Results indicated that individuals who, on average, slept <7 h each night showed inefficiencies in error-monitoring, as reflected by a reduction in amplitude of the error-related negativity (ERN) in comparison to those with longer sleep duration. These findings suggest that natural variations in sleep quantity are associated with atypical error detection.

Development of inhibition and switching: A longitudinal study of the maturation of interference suppression and reversal processes during childhood.

Inhibition and switching are executive functions (EFs) that have different developmental trajectories across childhood. The development of specific processes unique to each EF may contribute to these trajectories. Interference suppression and reversal were examined in a large sample of children aged 7 and 9 years (n = 120) and followed-up after two-years to investigate developmental trajectories of inhibition and switching. The N2 and P3b components provided neural correlates of conflict monitoring and attentional processing of conflict involved in interference suppression and reversal. Interference suppression improved over time, however, switching performance did not significantly change between 7 and 11 years. Improvements in correct RT with age and time indicated increased efficiency of stimulus evaluation, response preparation and execution. N2 amplitude decreased with both age and time, indicating less reliance on conflict monitoring to signal cognitive control to manage stimulus and response conflict. P3b amplitude modulations indicated that different amounts of attention were allocated to updating mental representations of interference suppression and reversal task features. These data indicated different developmental trajectories of specific processes unique to inhibition and switching across the childhood period of 7-11 years, providing further empirical evidence that 7-11 years is a critical period for cognitive development.

The error-related negativity (ERN) is an electrophysiological marker of motor impulsiveness on the Barratt Impulsiveness Scale (BIS-11) during adolescence.

OBJECTIVES: Previous studies have postulated that the error-related negativity (ERN) may reflect individual differences in impulsivity; however, none have used a longitudinal framework or evaluated impulsivity as a multidimensional construct. The current study evaluated whether ERN amplitude, measured in childhood and adolescence, is predictive of impulsiveness during adolescence. METHODS: Seventy-five children participated in this study, initially at ages 7-9 years and again at 12-18 years. The interval between testing sessions ranged from 5 to 9 years. The ERN was extracted in response to behavioural errors produced during a modified visual flanker task at both time points (i.e. childhood and adolescence). Participants also completed the Barratt Impulsiveness Scale - a measure that considers impulsiveness to comprise three core sub-traits - during adolescence. RESULTS: At adolescence, the ERN amplitude was significantly larger than during childhood. Additionally, ERN amplitude during adolescence significantly predicted motor impulsiveness at that time point, after controlling for age, gender, and the number of trials included in the ERN. In contrast, ERN amplitude during childhood did not uniquely predict impulsiveness during adolescence. CONCLUSIONS: These findings provide preliminary evidence that ERN amplitude is an electrophysiological marker of self-reported motor impulsiveness (i.e. acting without thinking) during adolescence.

Hemispheric asymmetries in rapid temporal processing at age 7 predict subsequent phonemic decoding 2 years later: A longitudinal event-related potential (ERP) study.

The asymmetric sampling in time hypothesis (AST) suggests that the left and right secondary auditory areas process auditory stimuli according to different sampling rates (Poeppel, 2003). We investigated whether asymmetries consistent with the AST are observable in children at age 7 and whether they become more pronounced at age 9. Data were collected from 50 children who attended a 2-day research program at age 7 and were followed up 2 years later. At both time points, children were presented with tone-pairs, each composed of two 50 ms, 1000 Hz, sinusoidal tones separated by inter-stimulus intervals (ISIs) of 25, 50, 100, or 200 ms. Stimuli were presented binaurally whilst the EEG was recorded. The Ta and Tb, which are components of the auditory event-related potential (ERP), were used as electrophysiological indices of auditory processing. There was no significant effect of age on Ta or Tb responses. Tb responses to the second tone of tone-pairs indicated a left-hemisphere preference for rapidly presented stimuli (50 ms ISI) and a right hemisphere preference for more slowly presented stimuli (100 and 200 ms ISI). The results provide evidence that auditory areas of the left hemisphere preferentially respond to fast temporal rates, and those of the right hemisphere preferentially respond to slow temporal rates in children at age 7 and 9. In 7-year-old children, leftward lateralisation of responses to rapidly presented tones predicted better phonemic decoding ability 2 years later, which suggests that hemispheric specialisation may be a precursor for subsequent phonemic decoding skills.

Allelic variation in dopamine D2 receptor gene is associated with attentional impulsiveness on the Barratt Impulsiveness Scale (BIS-11).

OBJECTIVES: Previous studies have postulated that noradrenergic and/or dopaminergic gene variations are likely to underlie individual differences in impulsiveness, however, few have shown this. The current study examined the relationship between catecholamine gene variants and self-reported impulsivity, as measured by the Barratt Impulsiveness Scale (Version 11; BIS-11) Methods: Six hundred and seventy-seven non-clinical adults completed the Barratt Impulsiveness Scale (BIS-11). DNA was analysed for a set of 142 single-nucleotide polymorphisms (SNPs) across 20 autosomal catecholamine genes. Association was tested using an additive regression model with permutation testing used to control for the influence of multiple comparison. RESULTS: Analysis revealed an influence of rs4245146 of the dopamine D2 receptor (DRD2) gene on the BIS-11 attention first-order factor, such that self-reported attentional impulsiveness increased in an additive fashion with each copy of the T allele. CONCLUSIONS: These findings provide preliminary evidence that allelic variation in DRD2 may influence impulsiveness by increasing the propensity for attentional lapses.

Error monitoring and empathy: Explorations within a neurophysiological context.

Past literature has proposed that empathy consists of two components: cognitive and affective empathy. Error monitoring mechanisms indexed by the error-related negativity (ERN) have been associated with empathy. Studies have found that a larger ERN is associated with higher levels of empathy. We aimed to expand upon previous work by investigating how error monitoring relates to the independent theoretical domains of cognitive and affective empathy. Study 1 (N = 24) explored the relationship between error monitoring mechanisms and subcomponents of empathy using the Questionnaire of Cognitive and Affective Empathy and found no relationship. Study 2 (N = 38) explored the relationship between the error monitoring mechanisms and overall empathy. Contrary to past findings, there was no evidence to support a relationship between error monitoring mechanisms and scores on empathy measures. A subsequent meta-analysis (Study 3, N = 125) summarizing the relationship across previously published studies together with the two studies reported in the current paper indicated that overall there was no significant association between ERN and empathy and that there was significant heterogeneity across studies. Future investigations exploring the potential variables that may moderate these relationships are discussed.

Assessing hemispheric specialization for processing arithmetic skills in adults: A functional transcranial doppler ultrasonography (fTCD) study.

BACKGROUND: A major model of the cerebral circuits that underpin arithmetic calculation is the triple-code model of numerical processing. This model proposes that the lateralization of mathematical operations is organized across three circuits: a left-hemispheric dominant verbal code; a bilateral magnitude representation of numbers and a bilateral Arabic number code. NEW METHOD: This study simultaneously measured the blood flow of both middle cerebral arteries using functional transcranial Doppler ultrasonography to assess hemispheric specialization during the performance of both language and arithmetic tasks. The propositions of the triple-code model were assessed in a non-clinical adult group by measuring cerebral blood flow during the performance of multiplication and subtraction problems. Participants were 17 adults aged between 18-27 years. We obtained laterality indices for each type of mathematical operation and compared these in participants with left-hemispheric language dominance. It was hypothesized that blood flow would lateralize to the left hemisphere during the performance of multiplication operations, but would not lateralize during the performance of subtraction operations. RESULTS: Hemispheric blood flow was significantly left lateralized during the multiplication task, but was not lateralized during the subtraction task. COMPARISON WITH EXISTING METHOD(S): Compared to high spatial resolution neuroimaging techniques previously used to measure cerebral lateralization, functional transcranial Doppler ultrasonography is a cost-effective measure that provides a superior temporal representation of arithmetic cognition. CONCLUSIONS: These results provide support for the triple-code model of arithmetic processing and offer complementary evidence that multiplication operations are processed differently in the adult brain compared to subtraction operations.

Verbal Learning and Memory in Cannabis and Alcohol Users: An Event-Related Potential Investigation.

Aims: Long-term heavy use of cannabis and alcohol are known to be associated with memory impairments. In this study, we used event-related potentials to examine verbal learning and memory processing in a commonly used behavioral task. Method: We conducted two studies: first, a small pilot study of adolescent males, comprising 13 Drug-Naive Controls (DNC), 12 heavy drinkers (HD) and 8 cannabis users (CU). Second, a larger study of young adults, comprising 45 DNC (20 female), 39 HD (16 female), and 20 CU (9 female). In both studies, participants completed a modified verbal learning task (the Rey Auditory Verbal Learning Test, RAVLT) while brain electrical activity was recorded. ERPs were calculated for words which were subsequently remembered vs. those which were not remembered, and for presentations of learnt words, previously seen words, and new words in a subsequent recognition test. Pre-planned principal components analyses (PCA) were used to quantify the ERP components in these recall and recognition phases separately for each study. Results: Memory performance overall was slightly lower than published norms using the standardized RAVLT delivery, but was generally similar and showed the expected changes over trials. Few differences in performance were observed between groups; a notable exception was markedly poorer delayed recall in HD relative to DNC (Study 2). PCA identified components expected from prior research using other memory tasks. At encoding, there were no between-group differences in the usual P2 recall effect (larger for recalled than not-recalled words). However, alcohol-related differences were observed in a larger P540 (indexing recollection) in HD than DNC, and cannabis-related differences were observed in a smaller N340 (indexing familiarity) and a lack of previously seen > new words effect for P540 in Study 2. Conclusions: This study is the first examination of ERPs in the RAVLT in healthy control participants, as well as substance-using individuals, and represents an important advance in methodology. The results indicate alterations in recognition memory processing, which even if not manifesting in overt behavioral impairment, underline the potential for brain dysfunction with early exposure to alcohol and cannabis.

N2 and P3 modulation during partial inhibition in a modified go/nogo task.

The neural response following the partial inhibition of responses can provide insight into the processes underlying response inhibition. We examined the N2 and P3 on trials where participants correctly responded to go stimuli, successfully inhibited their response to nogo stimuli, and nogo trials where they initiated but did not complete their response (partial inhibitions) in an adult sample (N=24, M(age)=21.17, SD(age)=3.52). An enhanced and delayed N2 was observed on partially inhibited compared to successfully inhibited nogo trials. Further analysis showed that this modulation was error-related. An enhanced central P3 was observed following successful inhibitions compared to correct go trials, but not following partial inhibitions. The results suggest that the central P3 enhancement is specific to the complete and successful inhibition of responses. Therefore, the absence of a central P3 on partial inhibitions could reflect insufficient inhibition or a monitored failure in inhibiting the response. Although, our findings provide support for the role of P3 in response inhibition, it raises questions about the processes involved in the subsequent inhibition or correction of the erroneous response. Further research examining the neural response following both partial and unsuccessful inhibitions could provide insight regarding these processes.

Electrophysiological evidence for lateralization of preparatory motor processes.

Event-related potentials were recorded during a warned choice reaction time task in which the warning signal was informative (it signaled the specific response to be required) or uninformative (it gave no response-specific information). The response signal specified a key press with either the middle or the ring finger of the left or the right hand. The informative warning signal facilitated reaction time in two separate protocols. The contingent negative variation elicited following the informative warning signal was larger than that following the uninformative warning signal, and this effect was larger over the left hemisphere than over the right hemisphere. This finding gives converging evidence that preparatory motor processes are predominantly lateralized to the dominant hemisphere.