Internal and external control: A two-factor model of amplitude change of event-related potentials

Long-term responses of internal environment dynamics in a freshwater lake to variations in external nutrient inputs: A model simulation approach

Lake restoration usually focuses on reducing external nutrient sources. However, when sediments contain nutrients accumulated over multiple years, internal nutrient release can delay restoration progress. In lake restoration and management, it is important to understand the dynamic relationship between nutrient concentrations in a lake and internal and external nutrient sources. In this study, we quantified external nutrient inputs through measurements and compared them with internal sediment release from simulation using the PCLake+ model. Additionally, we evaluated alterations in the internal nutrient release, lake nutrient concentrations, and algae biomass (chlorophyll-a) within the lake following varying degrees of reduction in external nutrient loads. The results demonstrate that the PCLake+ effectively simulated the lake's nutrient concentration and algae biomass. Based on the PCLake+ estimates, internal nutrient loads accounted for 51 % of the total nitrogen (N) and 80 % of the total phosphorus (P) loadings in Lake Erhai in 2019. In 2020, the total contributions were 43 % for TN and 72 % for TP. We simulated four scenarios where external nutrient inputs were reduced to 25 %, 50 %, 75 %, and 99.99 % of their original levels. The 40-year simulation showed that the lake's ecological system initially exhibited a fast internal response but reached equilibrium after eight years. P concentrations took longer to reach equilibrium compared to N concentrations, probably due to the stronger binding characteristics of P. To meet the water quality target in the future, it is necessary to reduce external N and P inputs into Lake Erhai by at least 23 % and 15 %, respectively, under current conditions. Although reducing external nutrient loads can indirectly lower internal nutrient loads, water management should address both external and internal loads simultaneously, as internal release cannot be effectively reduced by external reductions alone. Additionally, the lake's internal release may continue for several years, even with reductions in external inputs.

Comparing the 'When' and the 'Where' of Electrocortical Activity in Patients with Tourette Syndrome, Body-Focused Repetitive Behaviors, and Obsessive Compulsive Disorder

Background/Objectives: Tourette Syndrome (TS), Obsessive Compulsive Disorder (OCD), and Body-Focused Repetitive Behaviors (BFRB) are three disorders that share many similarities in terms of phenomenology, neuroanatomy, and functionality. However, despite the literature pointing toward a plausible spectrum of these disorders, only a few studies have compared them. Studying the neurocognitive processes using Event-Related Potentials (ERPs) offers the advantage of assessing brain activity with excellent temporal resolution. The ERP components can then reflect specific processes known to be potentially affected by these disorders. Our first goal is to characterize 'when' in the processing stream group differences are the most prominent. The second goal is to identify 'where' in the brain the group discrepancies could be. Methods: Participants with TS (n = 24), OCD (n = 18), and BFRB (n = 16) were matched to a control group (n = 59) and were recorded with 58 EEG electrodes during a visual counting oddball task. Three ERP components were extracted (i.e., P200, N200, and P300), and generating sources were modelized with Standardized Low-Resolution Electromagnetic Tomography. Results: We showed no group differences for the P200 and N200 when controlling for anxiety and depressive symptoms, suggesting that the early cognitive processes reflected by these components are relatively intact in these populations. Our results also showed a decrease in the later anterior P300 oddball effect for the TS and OCD groups, whereas an intact oddball effect was observed for the BFRB group. Source localization analyses with sLORETA revealed activations in the lingual and middle occipital gyrus for the OCD group, distinguishing it from the other two clinical groups and the controls. Conclusions: It seems that both TS and OCD groups share deficits in anterior P300 activation but reflect distinct brain-generating source activations.

Effects of benzodiazepine and orexin receptor antagonist on cognitive function revealed by auditory event-related potentials

BACKGROUND

Cognitive decline after oral administration of sedatives, such as benzodiazepines, is a serious side effect. Suvorexant, an orexin receptor antagonist, has a favorable tolerability and a limited side-effect profile.

AIM

The purpose of this study was to estimate the cognitive decline 1 day after oral medication with lormetazepam, a benzodiazepine, and suvorexant by comparing mismatch negativity (MMN) and P300 reflecting auditory discrimination function.

METHODS

Sixty healthy subjects (42 males) were randomly assigned to three groups receiving suvorexant 20 mg, lormetazepam 2 mg, or placebo in this double-blind, randomized control study. Event-related potential recordings during an auditory oddball task and a digit symbol substitution test (DSST) were performed 1 day after oral administration.

RESULTS

MMN, on the day after oral administration, was significantly attenuated in the lormetazepam group compared with the other two groups, but there was no difference between the suvorexant and placebo groups. No significant difference was found in P300 amplitudes and DSST scores among the three groups.

CONCLUSION

These findings suggest that suvorexant, unlike benzodiazepine, is not associated with cognitive deficits, as revealed by MMN but not P300. This study shows a neurophysiological difference in the effects of suvorexant and benzodiazepine on cognitive function.

EEG and behavioral correlates of attentional processing while walking and navigating naturalistic environments

The capacity to regulate one's attention in accordance with fluctuating task demands and environmental contexts is an essential feature of adaptive behavior. Although the electrophysiological correlates of attentional processing have been extensively studied in the laboratory, relatively little is known about the way they unfold under more variable, ecologically-valid conditions. Accordingly, this study employed a 'real-world' EEG design to investigate how attentional processing varies under increasing cognitive, motor, and environmental demands. Forty-four participants were exposed to an auditory oddball task while (1) sitting in a quiet room inside the lab, (2) walking around a sports field, and (3) wayfinding across a university campus. In each condition, participants were instructed to either count or ignore oddball stimuli. While behavioral performance was similar across the lab and field conditions, oddball count accuracy was significantly reduced in the campus condition. Moreover, event-related potential components (mismatch negativity and P3) elicited in both 'real-world' settings differed significantly from those obtained under laboratory conditions. These findings demonstrate the impact of environmental factors on attentional processing during simultaneously-performed motor and cognitive tasks, highlighting the value of incorporating dynamic and unpredictable contexts within naturalistic designs.

EEG Markers in Emotionally Unstable Personality Disorder-A Possible Outcome Measure for Neurofeedback: A Narrative Review

Objectives. There is growing evidence for the use of biofeedback (BF) in affective disorders, dissocial personality disorder, and in children with histories of abuse. Electroencephalogram (EEG) markers could be used as neurofeedback in emotionally unstable personality disorder (EUPD) management especially for those at high risk of suicide when emotionally aroused. This narrative review investigates the evidence for EEG markers in EUPD. Methods. PRISMA guidelines were used to conduct a narrative review. A structured search method was developed and implemented in collaboration with an information specialist. Studies were identified via 3 electronic database searches of MEDLINE, Embase, and PsycINFO. A predesigned inclusion/exclusion criterion was applied to selected papers. A thematic analysis approach with 5 criteria was used. Results. From an initial long list of 5250 papers, 229 studies were identified and screened, of which 44 met at least 3 of the predesigned inclusion criteria. No research to date investigates EEG-based neurofeedback in EUPD. A number of different EEG biomarkers are identified but there is poor consistency between studies. Conclusions. The findings heterogeneity may be due to the disorder complexity and the variable EEG related parameters studied. An alternative explanation may be that there are a number of different neuromarkers, which could be clustered together with clinical symptomatology, to give new subdomains. Quantitative EEGs in particular may be helpful to identify more specific abnormalities. EEG standardization of neurofeedback protocols based on specific EEG abnormalities detected may facilitate targeted use of neurofeedback as an intervention in EUPD.

Decreased effective connectivity between insula and anterior cingulate cortex during a working memory task after prolonged sleep deprivation

Total sleep deprivation (TSD) causes a decline in almost all cognitive domains, especially working memory. However, we do not have a clear understanding of the degree working memory is impaired under prolonged TSD, nor do we know the underlying neurophysiological mechanism. In this study, we recorded EEG data from 64 subjects while they performed a working memory task during resting wakefulness, after 24 h TSD, and after 30 h TSD. ANOVA was used to verify performance differences between 24 h and 30 h TSD in working memory tasks: (1) reaction time and accuracy hit rates, (2) P200, N200, and P300 amplitude and latency in measurements of event-related potential, as well as (3) effective connectivity strength between brain areas associated with working memory. Compared to 24 h TSD, 30 h TSD significantly decreased accuracy hit rates and induced a larger N200 difference waveform. The effective connectivity analysis showed that 30 h TSD also decreased beta frequency in effective connection strength from the right insular lobe to the left anterior cingulate cortex (ACC). Effective connection from the left ventrolateral prefrontal cortex to the left dorsolateral prefrontal cortex increased in the match condition of the 2-back task. In conclusion, 30 h TSD had a greater negative impact on working memory than 24 h TSD. This impairment of working memory is associated with decreased strength in the effective connection from the right insula to the left ACC.

Inter- and intra-individual coupling between pupillary, electrophysiological, and behavioral responses in a visual oddball task

Although the P3b component of the event-related brain potential is one of the most widely studied components, its underlying generators are not currently well understood. Recent theories have suggested that the P3b is triggered by phasic activation of the locus-coeruleus norepinephrine (LC-NE) system, an important control center implicated in facilitating optimal task-relevant behavior. Previous research has reported strong correlations between pupil dilation and LC activity, suggesting that pupil diameter is a useful indicator for ongoing LC-NE activity. Given the strong relationship between LC activity and pupil dilation, if the P3b is driven by phasic LC activity, there should be a robust trial-to-trial relationship with the phasic pupillary dilation response (PDR). However, previous work examining relationships between concurrently recorded pupillary and P3b responses has not supported this. One possibility is that the relationship between the measures might be carried primarily by either inter-individual (i.e., between-participant) or intra-individual (i.e., within-participant) contributions to coupling, and prior work has not systematically delineated these relationships. Doing so in the current study, we do not find evidence for either inter-individual or intra-individual relationships between the PDR and P3b responses. However, baseline pupil dilation did predict the P3b. Interestingly, both the PDR and P3b independently predicted inter-individual and intra-individual variability in decision response time. Implications for the LC-P3b hypothesis are discussed.

Cognition Impairment Prior to Errors of Working Memory Based on Event-Related Potential

Cognitive impairment contributes to errors in different tasks. Poor attention and poor cognitive control are the two neural mechanisms for performance errors. A few studies have been conducted on the error mechanism of working memory. It is unclear whether the changes in memory updating, attention, and cognitive control can cause errors and, if so, whether they can be probed at the same time in one single task. Therefore, this study analyzed event-related potentials in a two-back working memory task. A total of 40 male participants finished the task. The differences between the error and the correct trials in amplitudes and latencies of N1, P2, N2, and P3 were analyzed. The P2 and P3 amplitudes decreased significantly in the error trials, while the N2 amplitude increased. The results showed that impaired attention, poor memory updating, and impaired cognitive control were consistently associated with the error in working memory. Furthermore, the results suggested that monitoring the neurophysiological characteristics associated with attention and cognitive control was important for studying the error mechanism and error prediction. The results also suggested that the P3 and N2 amplitudes could be used as indexes for error foreshadowing.

Early onset cigarette smokers exhibit greater P300 reactivity to smoking-related stimuli and report greater craving

Adolescence is a period during which a number of critical neuromaturation processes occur and the vulnerability for developing nicotine dependence is extremely high. Thus, early-onset (EO; age < 16 years old), relative to late-onset (LO; age ≥ 16 years old), tobacco smoking may be uniquely deleterious for developmentally immature systems that regulate neural signaling reactivity. This study investigated how age of tobacco smoking onset affects neurophysiological measures of smoking cue reactivity and reported craving in adult smokers. EO smokers (EOS; n = 8; 4 females), LO smokers (LOS; n = 10; 5 females), and healthy non-smokers (HNS; n = 10; 5 females) participated in an event-related potential (ERP) cue reactivity study with tactile and image stimuli. Participants handled neutral objects during one interval and smoking-related objects during a second interval. After each interval, they viewed smoking-related, neutral, or arousing images using an oddball paradigm. P300 ERPs and craving for tobacco were recorded during each session. P300 amplitudes were significantly higher in central midline (Cz) channel to smoking, but not neutral or arousing, images after handling smoking objects. Specifically, Cz P300 smoking amplitudes were significantly greater in EOS, relative to LOS and HNS, and associated with greater craving at baseline. There were no other group differences in mood or craving. EOS exhibited greater P300 reactivity to smoking-related stimuli, relative to LOS, suggesting a more sensitized neural response. EO smoking during early neuromaturation may alter neurophysiological signaling involved in responding to smoking-related stimuli, which could impact the outcome of smoking cessation interventions.

Steering Demands Diminish the Early-P3, Late-P3 and RON Components of the Event-Related Potential of Task-Irrelevant Environmental Sounds

The current study investigates the demands that steering places on mental resources. Instead of a conventional dual-task paradigm, participants of this study were only required to perform a steering task while task-irrelevant auditory distractor probes (environmental sounds and beep tones) were intermittently presented. The event-related potentials (ERPs), which were generated by these probes, were analyzed for their sensitivity to the steering task's demands. The steering task required participants to counteract unpredictable roll disturbances and difficulty was manipulated either by adjusting the bandwidth of the roll disturbance or by varying the complexity of the control dynamics. A mass univariate analysis revealed that steering selectively diminishes the amplitudes of early P3, late P3, and the re-orientation negativity (RON) to task-irrelevant environmental sounds but not to beep tones. Our findings are in line with a three-stage distraction model, which interprets these ERPs to reflect the post-sensory detection of the task-irrelevant stimulus, engagement, and re-orientation back to the steering task. This interpretation is consistent with our manipulations for steering difficulty. More participants showed diminished amplitudes for these ERPs in the "hard" steering condition relative to the "easy" condition. To sum up, the current work identifies the spatiotemporal ERP components of task-irrelevant auditory probes that are sensitive to steering demands on mental resources. This provides a non-intrusive method for evaluating mental workload in novel steering environments.

Hazard levels of warning signal words modulate the inhibition of return effect: evidence from the event-related potential P300

Warning signal words are often used to convey valuable information about potential dangers in everyday life. In this study, we explored whether and how the hazard level of warning signal words modulated participants' attention to subsequent targets. Event-related potentials with high temporal resolution were employed in a cue-target paradigm. In this task, warning signal words with different hazard levels were used as cues. Participants were required to judge whether targets were presented on the screen horizontally or vertically. We found an inhibition of return (IOR) effect, i.e., participants had longer reaction times to validly cued targets than to invalidly cued targets. Accordingly, the IOR effect was reflected by a smaller P300 amplitude for invalidly cued targets compared to validly cued targets. Furthermore, the IOR effect was eliminated when the cues were high-hazard words. The dampening effect on the P300 was eliminated when the cues were high-hazard warning signal words. The lack of an IOR was attributed to participants' attentional bias to high-hazard stimuli, which are difficult for participants to disengage their attention from. The current study suggests that warning signal words are a particular type of stimulus that can override the IOR effect. Warning signal words with a high hazard level are more effective in successfully alerting people to risk in a hazardous environment.

Developmental changes in visuo-spatial working memory in normally developing children: event-related potentials study

OBJECTIVE

Working memory (WM) is very important for normal development. The fronto-parietal neuronal network supporting WM has already been well-studied. Less is known about the cortical activity changes during development of WM. We evaluated the maturation of visual WM network at the electrophysiological level in a group of normally developing children.

METHODS

Multichannel (n=31) event-related potentials (ERP) were measured during a visuo-spatial backmatching task in 69 childrens (6-16 years old). One-backmatching (BM1) and two-backmatching (BM2) tasks were performed. Age-related changes in behavioral parameters (commission and omission errors and reaction times) and ERP parameters (peak amplitudes and latencies) were analyzed between different ages.

RESULTS

Clear improvement in performance from young childhood toward adolescence was seen at the behavioral level: decrease of errors and fastening of reaction times. At the electrophysiological level age-related changes were seen in peak latencies and especially in amplitudes. Different peaks have different dynamics in amplitudes and latencies: early peak amplitude decreased and latency shortened with age, which was not always seen in late peaks. This reflects developmental changes in intensity and speed of WM processing. Later peaks were more clearly seen over the right hemisphere in older children, illustrating hemispheric lateralization in visuo-spatial working memory.

CONCLUSIONS

Our results indicate that not only at the behavioral but also at the electrophysiological level clear age-related dynamics in WM processing can be seen. Furthermore, with ERP we showed that different WM components follow different developmental trajectories.

SIGNIFICANCE

Our work demonstrates that age-related dynamics in intensity and speed of information processing during WM task is reflected in developmental changes in different ERP components. It also states that fronto-parietal visual WM network can be functional even before all its nodes are fully mature.

Electrophysiological indices of biased cognitive processing of substance-related cues: a meta-analysis

Several studies indicate that individuals with substance use disorders (SUD) exhibit biases in the cognitive processing of substance-related stimuli. These biases facilitate the detection of substance cues and have been argued to play a causal or perpetuating role in addiction. Two electrophysiological indices of cognitive processing, the P300 and Slow Potential (SP) components of the event-related potential (ERP), are associated with the deployment of attentional resources to motivationally relevant stimuli. In the present meta-analysis P300 (300-800ms) and SP (>800ms) amplitudes are used to investigate whether SUD persons show enhanced cognitive processing of substance cues relative to neutral cues as opposed to control participants. Results indicated the P300 and SP amplitude effect sizes were significantly larger in SUD participants than controls. This result is explained by substance users' motivated attention. Additional stratified moderator analyses revealed that both P300 and SP amplitudes were not moderated by electrode site (Fz vs. Pz), type of substance used (stimulants vs. depressants), substance use status (abstinent vs. non-abstinent), age, gender and task requirements (active vs. passive paradigms).

Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

Working memory in children with epilepsy: an event-related potentials study

PURPOSE

The aim of this study was to find out whether children with idiopathic epilepsy did show different cortical activation patterns compared to non-epileptic children during performance of a working memory task. To this end event-related potentials (ERPs) were measured during a visual 1-backmatching task. A quantitative analysis technique to analyze the ERP data, without any 'a priori' decisions on 'peak' presence, amplitudes or latencies, is used.

METHODS

46 children were tested (6-16 years old): 21 children with well-controlled "benign" epilepsy (benign rolandic epilepsy, n=9, idiopathic generalized epilepsy, n=12) and a control group of 25 non-epileptic children. Behavioral task performance and ERPs following both target and nontarget stimuli were compared across both study groups.

RESULTS

No differences were found in the number of omission errors or commission errors or in the reaction times between groups. However, ERPs following target stimuli showed significantly higher amplitude in the epilepsy group compared to the control group over frontal and central regions within the time window between 250 and 425 ms poststimulus, what coincides with the time window of target-nontarget stimulus discrimination.

DISCUSSION

Our study shows that children with benign, well-controlled epilepsy show a different cortical activation pattern during a visual working memory task. We hypothesize that they need more brain processing effort to achieve the same performance level as their age matched controls.

Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers

BACKGROUND AND PURPOSE

Animal studies show that histamine plays a role in cognitive functioning and that histamine H3-receptor antagonists, which increase histaminergic function through presynaptic receptors, improve cognitive performance in models of clinical cognitive deficits. In order to test such new drugs in humans, a model for cognitive impairments induced by low histaminergic functions would be useful. Studies with histamine H1-receptor antagonists have shown limitations as a model. Here we evaluated whether depletion of L-histidine, the precursor of histamine, was effective in altering measures associated with histamine in humans and the behavioural and electrophysiological (event-related-potentials) effects.

EXPERIMENTAL APPROACH

Seventeen healthy volunteers completed a three-way, double-blind, crossover study with L-histidine depletion, L-tyrosine/L-phenylalanine depletion (active control) and placebo as treatments. Interactions with task manipulations in a choice reaction time task were studied. Task demands were increased using visual stimulus degradation and increased response complexity. In addition, subjective and objective measures of sedation and critical tracking task performance were assessed.

KEY RESULTS

Measures of sedation and critical tracking task performance were not affected by treatment. L-histidine depletion was effective and enlarged the effect of response complexity as measured with the response-locked lateralized readiness potential onset latency.

CONCLUSIONS AND IMPLICATIONS

L-histidine depletion affected response- but not stimulus-related processes, in contrast to the effects of H1-receptor antagonists which were previously found to affect primarily stimulus-related processes. L-histidine depletion is promising as a model for histamine-based cognitive impairment. However, these effects need to be confirmed by further studies.

Influence of comorbid obsessive-compulsive symptoms on brain event-related potentials in Gilles de la Tourette syndrome

Approximately 30 to 50% of people suffering from Gilles de la Tourette Syndrome (GTS) also fulfill diagnostic criteria for obsessive-compulsive disorder (OCD). Despite this high degree of comorbidity, very few studies have addressed the question of obsessive-compulsive symptoms (OCS) in GTS patients using specific brain event-related potentials (ERP) responses. The aim of the current study was to quantify neurocognitive aspects of comorbidity, using ERPs. Fourteen adults with GTS (without OCD) were compared to a group of 12 participants with GTS and comorbid obsessive-compulsive symptoms (GTS+OCS), to a group of 15 participants with OCD and to a group of 14 control participants without neurological or psychiatric problems. The P200 and P300 components were recorded during a visual counting oddball task. Results showed intact P200 amplitude in all groups, whilst the P300 amplitude was affected differentially across groups. The P300 oddball effect was reduced in participants in both OCD and GTS+OCS groups in the anterior region. However, the P300 oddball effect was significantly larger in participants of the GTS group compared to all other groups, mostly in the parietal region. These findings suggest that adults with GTS are characterized by enhanced working memory updating processes and that the superimposition of OCS can lead to a reduction of these processes. The discrepancy between our findings and results obtained in previous studies on GTS could reflect the modulating effect of OCS on late ERP components.

Behavioural and electrophysiological measures of task switching during single and mixed-task conditions

In order to understand how the brain prepares for and executes a switch in task demand, we measured reaction time (RT), accuracy, and event-related brain potentials associated with performance in single and mixed-task blocks using a cued design. Our results show that trials which repeat in a mixed-task block (repeat trials) were more demanding than trials which repeated in a single-task block, as reflected by the presence of a RT mixing cost and by the presence of a smaller target-locked positivity (P3b) on repeat trials. Within a mixed-task block, repeat and switch trials also differed, where repeat trials showed evidence of greater preparation (larger cue-locked negativity), more efficient target processing (larger target-locked P3b), and shorter RTs. In addition, the cue-locked negativity difference remained despite equating repeat and switch trials on RT, suggesting that this negativity difference is specific to the switching process. Our results are discussed in light of existing models of task switching.

Negative Priming in a Numerical Piaget-like Task as Evidenced by ERP

Inhibition is a key executive function in adults and children for the acquisition and expression of cognitive abilities. Using event-related potentials in a priming adaptation of a Piaget-like numerical task taken from developmental psychology, we report a negative priming effect in adults measured just after the cognitive inhibition of a misleading strategy, the visuospatial length-equals-number bias. This effect was determined in the N200 information processing stage through increased N200 amplitude. We show here that for accuracy in numerical quantification, the adult brain still had to control the childlike cognition biases that are stored in a kind of “developmental memory.”

Indices of slowness of information processing in head injury patients: tests for selective attention related to ERP latencies

We explored the relation between neuropsychological (attention tests involving time constraints) and neurophysiological (N2 and P3 event-related potential (ERP) latencies) indices of slowness of information processing after closed head injury (CHI). A group of 44 CHI patients performed worse than healthy controls on most neuropsychological indices, and had significantly longer ERP latencies. Significant correlations between neuropsychological measures and ERP latencies were found only for the 3 subtasks of the Stroop test. In additional multiple regression analyses P3 latency appeared the best predictor in Stroop Color only. A possible explanation is that stimulus evaluation processes comprise a relatively large part of performance on this subtask. In Stroop Color-Word, response related processes are supposed to play a greater role, reducing the role of the preceding input related processes. The absence of significant correlations between P3 latency and scores on the other attention tests suggests a relatively small role of stimulus evaluation processes in these tasks, implying that these tasks are not sensitive to slowness of these processes. The Stroop test appears to be the only attention test administered in which slowness in stimulus evaluation processes requiring selective attention contributes significantly to the delay in final performance on the task.

Age-related changes in involuntary and voluntary attention as reflected in components of the event-related potential (ERP)

The present paper provides an overview of age-related changes in both involuntary and voluntary attention in adult subjects as manifested in scalp-recorded ERPs. A decline in orienting with old age was inferred from a substantial reduction with age in the magnitude of deviance-related ERP components like MMN, target as well as nontarget P3s, novelty P3 and N400. A review of focused attention studies further suggested that old and young subjects do not differ substantially in the quality of attentional operations. In old subjects early selection processes, as reflected in their selection potentials, have a somewhat slower onset than in young subjects, especially in conditions in which selection is based upon complex discrimination of stimulus features. Furthermore, the global pattern emerging from visual and memory search studies is that search-related negativities in the ERPs are smaller and of longer duration in old than in young subjects over the central and anterior scalp sites. These effects could indicate that controlled search is less intense or takes more time per search operation in old than in young subjects. At more posterior scalp sites there was tendency towards an enhanced search-related negativity that could reflect a specific difficulty (or compensatory increase in mental effort) of old subjects in spatially locating targets in complex visual fields.

P300 event-related brain potential and personality in depression

P300 is an event-related brain potential (ERP) particularly interesting to the study of cognitive processes in normal subjects and in psychopathology. P300 has been applied in depression with controversial results. A major source for these controversial results could result from the diversity of depressed patients included in the different studies. Supporting this assumption, impulsivity, blunted affect, suicidal behavior and psychotic features significantly influence P300 amplitude. However, no data are available on the possible influences of the personality of depressed patients on P300. Since personality is related to P300 in normal subjects, the aim of the present study is to investigate the relationship between ERPs (P200, N200, and P300) and the Temperament and Character Inventory (TCI) in 54 depressed patients. The main results of the study concern the absence of major correlations between personality dimensions as assessed by the TCI and ERP parameters among depressed patients. Only weak partial positive correlations relate N200 latency with harm avoidance, and P300 amplitude (Pz) with the self-directedness dimension. N200 amplitude is also negatively correlated to persistence. However, the preliminary nature of the presented results with respect to the weak statistical significance should be underlined.

[The p300 cognitive event-related potential. I. Theoretical and psychobiologic perspectives]

The P300 is a positive wave which arises when an attended stimulus is detected. Its parameters depend on a number of variables, in particular the subject's mental state, the task that has to be accomplished, the significance of the stimulus, and the degree of attention. It can be recorded with accuracy, and the different stages of information processing can therefore be analyzed. The P300 wave shows the modifications in neuronal activity which take place during the cognitive process: P300 latency provides an indirect indication of the duration of the processes involved in stimulus discrimination while its amplitude, which is influenced by a number of variables, provides an index of the intensity of the energetic activation or arousal involved. The P300 wave consists of several components which reflect distinct information-processing events (P3a, P3b, P3e, P-SR, P-CR). According to the theoretical models, it is hypothesized that P300 could either represent the adaptation of the working memory to further environmental input ('context updating'), or indicate a closing process ('context closure') in information processing. As regards the physiological aspect of P300 and its association with cortical networks, various studies have suggested that several cortical generators of P300 may co-exist: the medial temporal lobe, the temporo-parietal junction, and the medial and lateral frontal lobe. Psychopharmacological studies have shown that different neurotransmitter systems are involved in the generation and modulation of P300, namely the cholinergic, noradrenergic, dopaminergic, serotoninergic and gabaergic systems. It appears that the noradrenergic agonists increase the amplitude of P300, dopaminergic agonists may have a biphasic effect (increase/reduction), while cholinergic antagonists and gabaergic agonists reduce P300 amplitude and prolong its latency.

P300 and personality: an investigation with the Cloninger's model

The relationships between P300 and personality have been explored mainly in reference to the model of personality described by Eysenck because of its biological bases. Recently, Cloninger and his colleagues have proposed a model of personality based on four temperaments and three characters. The Temperament and Character Inventory (TCI) is a 226-item self-questionnaire developed to assess these seven dimensions of personality. In the present study, the relationships between these dimensions of personality and P300 have been investigated in 43 normal subjects. The results show that P300 amplitude is positively correlated with the novelty seeking dimension and negatively correlated with the harm avoidance dimension. In contrast, the other dimensions of the TCI were not related to P300 amplitude. Moreover, P300 latency and reaction time were not associated with the TCI dimensions of personality. This study confirms that personality is related to P300.

Knowledge inhibition and N400: a study with words that look like common words

In addition to their own representations, low frequency words, such as BRIBE, can covertly activate the representations of higher frequency words they look like (e.g., BRIDE). Hence, look-alike words can activate knowledge that is incompatible with the knowledge corresponding to accurate representations. Comparatively, eccentric words, that is, low frequency words that do not look as much like higher frequency words, are less likely to activate incompatible knowledge. This study focuses on the hypothesis that the N400 component of the event-related potential reflects the inhibition of incompatible knowledge. This hypothesis predicts that look-alike words elicit N400s of greater amplitudes than eccentric words in conditions where incompatible knowledge is inhibited. Results from a single item lexical decision experiment are reported which support the inhibition hypothesis.

Event-related-potential (ERP) reflections of mental resources: a review and synthesis

In this review studies are evaluated that have utilized middle-latency and late components of the event-related potential (ERP) as indices of the activation of processing resources. Processing resources are defined as energetical systems that modulate cognitive processes or data processing systems. An essential element of the resource conceptualization is the idea that processing structures receive not only information input but also input from these energetical systems. It is argued further that the principal role of these systems is to provide the 'gain' for the data processing systems. In reviewing these studies special attention is paid to factors affecting the amplitude of ERP components in single- and dual-task studies, and to the inferences that can be drawn about which particular types of processing resources are reflected in these changes in component amplitudes. Finally, a working model is presented relating middle-latency and late ERP components to specific perceptual, perceptual-central and central processing resources.

Slow negative brain potentials as reflections of specific modular resources of cognition

The paper summarizes a series of experiments in which the topography and the amplitude of slow event-related brain potentials (slow ERPs) was studied in cognitive tasks which imposed different amounts of load on functionally distinct processing modules. The results suggest that the topography of slow ERPs reflects the relative activation/inactivation of distinct cortical cell assemblies while the absolute amplitude of the negative maximum seems to reflect how much a particular cell assembly is activated at a particular time. Translated into the terminology of cognitive resource theories one could say that tasks which evoke distinct slow wave patterns draw on independent resources. Likewise, the amplitude of a slow wave pattern could be related to the construct of resource allocation, i.e. the larger the amplitude of a slow wave pattern the more resources of a particular type are allocated to a task. These findings are discussed with respect to possible generator mechanism of slow waves and in relation to possible causes of capacity limitations of the human information processing system.

Cognitive and emotional deficits in early stages of HIV infection: an event-related potentials study

1. In order to inventory different Event-Related Potentials (ERP) modifications in HIV-infection the authors have evaluated 23 HIV-positive subjects and 12 HIV-negative subjects. ERP were recorded during an auditory oddball task. 2. Electrophysiological results showed that the latency of the N100 component of the ERP was significantly increased in HIV-positive subjects compared to the HIV-negative subjects. The latency of the N200 component of the ERP showed a similar tendency which just failed to reach significance when considering HIV-positive subjects vs HIV negative subjects. This result was in agreement with the literature which reported increased latencies in HIV infection. 3. Considering all subjects the authors have observed a correlation between the amplitude of the P300 and the emotional deficit. This correlation was stronger in subjects who presented an emotional deficit and was independent of any other psychopathological symptom. 4. The use of ERP appeared to be a sensitive technique to detect subclinical manifestations in HIV asymptomatic subjects and therefore would help to identify subjects at higher risk for developing cognitive impairments.

Heterogeneity of information-processing alterations according to dimensions of depression: an event-related potentials study

To identify alterations in elementary cognitive operations according to dimensions of depression, two stages of information processing, namely the response choice and the motor preparation stages, were explored using an event-related potential paradigm in two subgroups of depressed patients (retarded and blunted affect versus anxious-agitated and impulsive) compared to controls. Two results are common to all depressed patients: a slow encoding of stimuli (P1 wave) and a prolonged processing of stimulus-response compatibility (after P3b). This is compensated by a global velocity increase in stimulus evaluation or decision making (P3b) in anxious-agitated patients or, on the contrary, cumulated with its velocity decrease in retarded-blunted-affect patients. Such results could provide an explanation for the massive retardation observed in blunted-affect patients, contrary to anxious-agitated patients, whose normal reaction times may come from a very high energetical involvement at the P3b level. Results as a whole suggest that impairments in blunted-affect patients concern effort mechanisms, whereas those in anxious-agitated patients concern perceptual processes.

Aging, caffeine, and information processing: an event-related potential analysis

Structural and energetic processes in information processing were studied in young and elderly subjects. A visually focussed selective search task was used, in which subjects had to select relevant information, followed by controlled memory search processes to locate a target item. Caffeine was used to manipulate the energetic state of the subjects. During task performance event-related potentials (ERPs) and reaction time (RT) were recorded. Subjects were 15 young and 15 elderly healthy, non-smoking, moderate caffeine consumers (250-600 mg/day). Before the experimental sessions they abstained from caffeine for > or = 12 h. In the experiment subjects received 250 mg caffeine or placebo dissolved in decaffeinated coffee. RT data seem to indicate that aging effects are at least partly due to a shift in the speed-accuracy trade-off. ERP results provide evidence for decreased levels of energy resources in the elderly. The identification of relevant information and stimulus evaluation processes were delayed in the elderly, suggesting an additional effect of aging on structural processes. Caffeine improved performance and increased the amplitude of the N1, N2b, and P3b, in both young and old subjects. These results suggest that caffeine makes more energy resources available for task performance. The effects of aging on P3b latency were counteracted by caffeine. Other caffeine effects did not differ significantly between young and elderly subjects.

Cognitive event-related potential in hepatic encephalopathy

A study of auditory P300 was performed on 24 patients with cirrhosis of the liver: 13 patients with hepatic encephalopathy (HE grade 1-2) and 11 patients without clinical encephalopathy (HE grade 0). The patients were also assessed using spontaneous EEG and neuropsychological methods: Mini Mental State, Digit Span and Number Connection Test. The P3 latency was found to be significantly increased in all patients (100%) with HE grade 1-2 and in 6 patients (54.5%) with HE grade 0. The clinical value of using the P300 latency in the hepatic encephalopathy is subsequently discussed.

Children of alcoholics: attention, information processing and event-related brain potentials

Recent studies on biological markers and risk factors for alcoholism have distinguished between nonalcoholic individuals with a family history of alcoholism and those without such a family history on measures of event-related brain potentials. The main finding of these "high-risk" studies is a smaller amplitude of the P300 component in males with a history of paternal alcoholism. This relationship between P300 amplitude and a family history of paternal alcoholism has been observed in adults and children. Consequently, several authors have suggested that a reduced P300 amplitude could serve as a vulnerability marker for alcoholism. We address several conceptual and methodological issues involved in the study of event-related potentials in children at high risk for alcoholism. Subsequently, the ongoing high-risk study of the Amsterdam Institute for Addiction Research is described briefly.

Influence of caffeine on selective attention in well-rested and fatigued subjects

Effects of caffeine were studied in a visual focused selective search task in well-rested and fatigued subjects. A dose of 200 + 50 mg caffeine or placebo, dissolved in decaffeinated coffee, was administered in a double-blind and deceptive fashion. The task was to detect a target letter on one diagonal of a visual display designated as relevant and ignore stimuli presented on the irrelevant diagonal. Behavioral measures were supplemented by event-related potential (ERP) measures. Subjects reacted faster in the caffeine condition. Caffeine enhanced the N1 and the N2b components. Selection of relevant information apparently was more adequate in this condition. Search negativity was not affected by caffeine. Caffeine effects on the P3 elicited by target letters were more pronounced in the fatigued than in the well-rested subjects, indicating that the effects of caffeine are dependent on the state of the subject. The results suggest that caffeine has specific rather than general effects on information processing.

Mental processing during reactions toward and away from a stimulus: an ERP analysis of auditory congruence and S-R compatibility

In its first usage, stimulus-response (S-R) compatibility defined strict S-R relationships. The later use of more complex two-dimensional stimuli led to the formulation of the Simon effect as a tendency to respond toward the side of stimulation. Ragot and Guiard (1992, European Journal of Cognitive Psychology, 4, 219-232) observed an inversion of the Simon effect in the auditory modality. The present study was undertaken to present a more thorough observation of this seemingly paradoxical inversion through the use of brain event-related potentials (ERPs). Two experimental variables were manipulated: (a) stimulus congruence, expressing the degree of correspondence between two randomly varying conflictual or nonconflictual attributes of the stimulus (spoken word droite or gauche presented to the right or left ear), and (b) S-R compatibility as such, expressing the relationship between the relevant stimulus attribute (word) and the responding hand. Results show that the nature of the spoken word acts on N100 latency and is therefore the first stimulus attribute to be processed. Data on P300 indicate that S-R compatibility is the last variable to be taken into account. The observed results are integrated into a cascade/parallel model.

Maturational changes in ERPs to orthographic and phonological tasks

Children from 7 to 18 years of age (divided into 2 year groupings, i.e., 7-8, 9-10, etc.) and young adults were studied (total of 84 subjects). ERPs were recorded from 19 electrodes during 2 visual oddball tasks: an orthographic task requiring responses to letters with a closed loop (e.g., a, p), and a phonological task, requiring responses to letters that rhymed with 'v' (e.g., c, p). N2 and P3 peak latencies and amplitudes were measured on the difference potentials. RTs decreased with age and between tasks (orth < phon). N2 and P3 latencies decreased with age and were shorter for the orthographic than phonological task. P3 amplitude was lower for the phonological task; the cortical distribution varied significantly as a function of age and task. The task differences in distribution were more marked in the younger age groups. Hemispheric asymmetries in P3 amplitudes were seen in the phonological task. The orthographic task required simple visual feature recognition and the phonological task required a visual-to-auditory translation. The interaction effects suggest that cortical utilization differs for these tasks, with greater age-related changes for the phonological task.

Information processing in children with minor neurological dysfunction: behavioural and neurophysiological indices

Minor neurological dysfunction (MND) refers to deviant function of the central nervous system in the absence of localizable neurological disorders. Children with no signs (n = 28) and with varying grades of MND (n = 48), classified according to failure on circumscript neurological subsystems, were administered selective and sustained attention tasks at the age of twelve. During the execution of one of the tasks, electrocortical activity of the brain was recorded at the Fz, Cz, Pz and Oz scalp locations. Of main interest were behavioural and electrophysiological indices of deficits in attentional control. With respect to the latter category, the investigation was focused on differences in event-related potential amplitudes reflecting subprocesses of cognitive processing (processing negativity, P300). Following a linear stage model of information processing, it was found that children who failed on three or more neurological subsystems (in particular on fine manipulation and coordination), exhibited deficits in the encoding, search and decision stages of processing. Furthermore, the children with MND showed a reduced positive parietal shift on target presentation. Under complex task conditions, children without MND showed a decrease in P300 amplitude which reflects the impact of processing negativity as a result of increased task demands; this effect was absent in children with MND. These electrocortical differences suggest imbalances in the external and internal neural regulation of the flow of information in the brain.