Single-trial event-related potentials and autonomic measures of the orienting reflex

We aimed to clarify the event-related potentials (ERPs) associated with elicitation and habituation of the basic Orienting Reflex (OR). Participants were presented with 16 innocuous tones, alternating in intensity, at long variable inter-stimulus intervals, with no task. This allowed us to examine stimulus novelty and intensity effects in the absence of stimulus-related task demands. Single-trial ERPs were extracted to obtain estimates of the early N1 and the late positive complex (LPC) to each stimulus. Electrodermal responses showed substantial main effects of trials and intensity, supporting their functionality as an OR index. Cardiac deceleration showed no systematic change with intensity or trials, suggesting that it marks the transient onset of each stimulus, early in the stimulus-processing sequence. Respiratory pause showed a substantial main effect of trials but no intensity effect, suggesting that it reflects an intermediate processing stage. A main effect of intensity, but no simple trial effect, was apparent in the N1, suggesting that it reflects a different intermediate processing stage. The subsequent LPC showed only a topographic interaction with trials and intensity, failing to support any substantive role in OR processing. These different stimulus-response profiles are discussed in the context of a sequential processing model of the OR.     

Pupillary responses and event-related potentials as indices of the orienting reflex

This study examined skin conductance responses, the late positive complex of the event-related potential, and pupillary dilation responses as autonomic and central correlates of the orienting reflex (OR) in the context of indifferent and significant stimuli. In particular, we aimed to clarify the inconsistencies surrounding the pupillary dilation response as an OR index. An auditory dishabituation paradigm was employed, and physiological measures were recorded from 24 participants. Response decrement to a repeated stimulus, response recovery to a change stimulus, and subsequent dishabituation were assessed. Findings confirmed expectations that the skin conductance response and the late positive complex are indices of the OR. The pupillary dilation response, however, demonstrated an unexpected sensitivity to stimulus novelty only, while the prestimulus measure of tonic pupil diameter showed the significance effect that was expected of the phasic measure. Together, these findings argue against the suggestion that the pupillary dilation response is an OR index. The diverse results obtained from this experiment contribute to our understanding of the OR, and provide impetus for further research with a variety of paradigm manipulations.     

Trial effects in single-trial ERP components and autonomic responses at very long ISIs

Single-trial data from autonomic and ERP measures were used to capture the rapidly decreasing initial responses characteristic of the orienting reflex (OR) to repeated stimuli. Stimulus–response patterns were compared to determine central analogues of autonomic indices of processes leading to the OR, and the OR itself. Participants were presented with 12 indifferent tones in an auditory dishabituation paradigm. Temporal principal component analysis (PCA) decomposed EOG-corrected ERP data for 16 subjects. Response patterns of ERPs, cardiac, and respiratory responses were compared to the phasic skin conductance response (SCR). SCR decremented over trials, recovered on the change trial, and dishabituated to the representation of the standard, meeting the formal definition of habituation required of the OR. The evoked cardiac response showed no trial effects. Respiratory pause (RP) decreased linearly over trials, recovering marginally on the change trial. Nine identifiable ERP components were extracted: P1, N1-3, N1-1, processing negativity (PN), P2, P3a, P3b, a novelty-sensitive P3 component (labelled HabP3), and the slow wave (SW). P3b and SW showed decrement over trials, but with no recovery, HabP3 showed decrement and increased response on the change trial, while the P1, N1 subcomponents, P2 and P3a were insensitive to novelty. Stimulus–response patterns of the RP and HabP3 suggest sensitivity to novelty processing, while the P1, N1-3, N-1, PN, P2, P3a and cardiac deceleration appear to mark processing prior to novelty, such as stimulus transient detection (cardiac deceleration) and/or intensity processing. This study supports predictions of preliminary process theory, demonstrating fractionation of 3 autonomic and 9 ERP components to novelty, and disconfirming the unitary nature of the OR.     

Event‐related EEG time‐frequency PCA and the orienting reflex to auditory stimuli

We recently reported an auditory habituation series with counterbalanced indifferent and significant (counting) instructions. Time‐frequency (t‐f) analysis of electrooculogram‐corrected EEG was used to explore event‐related synchronization (ERS)/desynchronization (ERD) in four EEG bands using arbitrarily selected time epochs and traditional frequency ranges. ERS in delta, theta, and alpha, and subsequent ERD in theta, alpha, and beta, showed substantial decrement over trials, yet effects of stimulus significance (count vs. no‐task) were minimal. Here, we used principal components analysis (PCA) of the t‐f data to investigate the natural frequency and time combinations involved in such stimulus processing. We identified four ERS and four ERD t‐f components: six showed decrement over trials, four showed count > no‐task effects, and six showed Significance × Trial interactions. This increased sensitivity argues for the wider use of our data‐driven t‐f PCA approach.     

Olfaction in the psychosis prodrome: Electrophysiological and behavioral measures of odor detection

Smell identification deficits (SIDs) are relatively specific to schizophrenia and its negative symptoms, and may predict transition to psychosis in clinical high-risk (CHR) individuals. Moreover, event-related potentials (ERPs) to odors are reduced in schizophrenia. This study examined whether CHR patients show SIDs and abnormal olfactory N1 and P2 potentials. ERPs (49 channels) were recorded from 21 CHR and 20 healthy participants (13 males/group; ages 13–27 years) during an odor detection task using three concentrations of hydrogen sulfide (H₂S) or blank air presented unilaterally by a constant-flow olfactometer. Neuronal generator patterns underlying olfactory ERPs were identified and measured by principal components analysis (unrestricted Varimax) of reference-free current source densities (CSD). Replicating previous findings, CSD waveforms to H₂S stimuli were characterized by an early N1 sink (345 ms, lateral–temporal) and a late P2 source (600 ms, mid-frontocentroparietal). N1 and P2 varied monotonically with odor intensity (strong > medium > weak) and did not differ across groups. Patients and controls also showed comparable odor detection and had normal odor identification and thresholds (Sniffin' Sticks). However, olfactory ERPs strongly reflected differences in odor intensity and detection in controls, but these associations were substantially weaker in patients. Moreover, severity of negative symptoms in patients was associated with reduced olfactory ERPs and poorer odor detection, identification and thresholds. Three patients who developed psychosis had poorer odor detection and thresholds, and marked reductions of N1 and P2. Thus, despite the lack of overall group differences, olfactory measures may be of utility in predicting transition to psychosis among CHR patients.     

Clarifying the sequential processes involved in a cued continuous performance test

We aimed to clarify sequential processes for cue and imperative stimuli (targets/nontargets) in a continuous performance test (CPT), and how the preparatory contingent negative variation (CNV) affects physiological and behavioral responses. Single‐trial event‐related potentials (ERPs) obtained from 70 participants during a cued CPT were baselined to the cue (BtC) to include the CNV, or to the imperatives (BtI) to remove the CNV. Principal components analysis obtained cue and imperative ERP components, and congruence coefficients (r_c) evaluated similarities. The cue and imperative components were comparable, more so for the BtI‐ than BtC‐imperative components (r_c = .85). N1, PN, P2, N2c, and SW components were similar, but not the N2b and P3s. Imperative ERPs were largely unaffected by the resolving CNV. Similar cue and imperative components suggest similar sequential processes, while preparatory CNV activity enhanced physiological and behavioral responses.     

The neural process of hazard perception and evaluation for warning signal words: Evidence from event-related potentials

Warning signs have been widely applied to industrial production. As an important component of warning signs, warning signal words were mostly studied by using questionnaire. This study used event-related potentials (ERPs) to explore neural temporal features during the processing of warning signal words in human brain, and found that there were two stages involved in processing warning signal words, providing an electrophysiological evidence for a previous warning information processing model, the Communication-Human Information Processing Model (C-HIP). Previous behavioral studies indicated that the subjective hazard perception of participants facilitates their attention to the warning sign, and people can get hazard information from warning words. Our results provided direct evidence for these conclusions. The present findings of significant differences in subjective hazard perception for warning words among individuals showed the importance and necessity of training for people to get the similar understanding of these words. Our results implicated that the warning words reflecting the same hazard level used in the warning sign should be somewhat changed, at the same time, convey equally or similarly hazardous information, to avoid desensitization and habituation due to overuse of them.     

A neurophysiological deficit in early visual processing in schizophrenia patients with auditory hallucinations

Existing 67‐channel event‐related potentials, obtained during recognition and working memory paradigms with words or faces, were used to examine early visual processing in schizophrenia patients prone to auditory hallucinations (AH, n = 26) or not (NH, n = 49) and healthy controls (HC, n = 46). Current source density (CSD) transforms revealed distinct, strongly left‐ (words) or right‐lateralized (faces; N170) inferior‐temporal N1 sinks (150 ms) in each group. N1 was quantified by temporal PCA of peak‐adjusted CSDs. For words and faces in both paradigms, N1 was substantially reduced in AH compared with NH and HC, who did not differ from each other. The difference in N1 between AH and NH was not due to overall symptom severity or performance accuracy, with both groups showing comparable memory deficits. Our findings extend prior reports of reduced auditory N1 in AH, suggesting a broader early perceptual integration deficit that is not limited to the auditory modality.     

Effects of acoustic distortion and semantic context on event-related potentials to spoken words

This study examined the neurophysiological effects of acoustic degradation on auditory semantic processing. Event-related potentials were recorded to target words presented in a sentence context. Targets were semantically congruent or incongruent with the context, which was acoustically intact or low-pass filtered. In unaltered contexts, N400 amplitude was significantly greater for incongruent than congruent words. Filtering significantly reduced this effect, even though participants were highly accurate in interpreting the degraded stimuli, as shown by an anomaly detection task. This reduction in the N400 effect appeared to be driven by decreased N400 amplitudes over posterior electrode sites for incongruent targets. These results demonstrate that acoustic degradation influences the neural response to words in context by reducing the availability of semantic information in on-line sentence comprehension.     

The Müller–Lyer illusion seen by the brain: An event-related brain potentials study

In two experiments, event-related brain potentials (ERPs) were used to examine the neural correlates of a visual illusion effect in Müller–Lyer illusion tasks (illusion stimuli) and baseline tasks (no-illusion stimuli). The behavioral data showed that the illusion stimuli indeed yielded an illusion effect. Scalp ERP analysis revealed its neurophysiological substrate: the Müller–Lyer illusion tasks (Illusion tasks 1–3) elicited a more negative ERP deflection than did the baseline tasks about 400 ms after onset of the stimuli. Dipole source analysis of the difference wave (Illusion task 2–Baseline task 1) and the original waveforms of the different conditions (Illusion tasks 2 and 3 and Baseline task 2) indicated that the anterior cingulate cortex (ACC)/superior frontal cortex may contribute to the illusion effect, possibly in relation to high-level cognitive control. The results indicated that apparent distortions of the Müller–Lyer illusion might be influenced by top-down control.     

积极情绪对整体和局部知觉的影响:事件相关电位研究

目的:采用启动范式和事件相关电位方法,研究积极情绪如何调制视觉系统选择性加工刺激整体特征和局部特征的神经机制。方法:对22名大学生,采用Neuroscan公司64导脑电系统记录其在3种情绪图片启动条件下执行整体和局部加工任务时的事件相关电位(ERPs)和行为学结果。结果:250～320ms时间段内,积极情绪和中性情绪启动条件下整体加工引起的事件相关脑电波幅大于局部加工的脑电波幅(P<0.01),差异主要分布于额-中央区;350～500ms时间段内,积极情绪启动的整体加工(局部加工)诱发的事件相关脑电波幅大于消极情绪启动的整体加工(局部加工)诱发的脑电波幅(P<0.01),差异主要分布于顶-枕区。结论:积极情绪促进整体和局部知觉加工的神经机制,可能存在差别,ERP早期成分的差异可能与额-中央区活动关系密切,晚期成分与顶-枕区活动联系可能更为密切。     

Associations between the tumor necrosis factor alpha gene (-308G→A) and event-related potential indices of attention and mental rotation

The tumor necrosis factor alpha (TNF-α) is a cytokine that exerts neuroprotective and neurodegenerative effects. While some research suggests enhancing effects of the TNF-α gene (TNF-α -308G→A) on cognitive function, further research is needed to clarify the association between the TNF-α gene and specific areas of cognitive performance including their neurophysiological correlates. In this study we examine association of the TNF-α -308G→A single nucleotide polymorphism (rs1800629) with attention and mental rotation performance in an event-related potential (ERP) study in healthy participants (n=67). The results show that carriers of the -308 A allele display elevated attentional processes (i.e. a stronger N1) as compared to the GG genotype group. Mental rotation performance varied across genotypes when demands on mental rotation were high. Here, carriers of the -308 A allele performed better than the GG genotype group. This is paralleled by the neurophysiological data showing genotype-dependent variations in parietal positivities only under the condition of high demands on mental rotation. The finding of enhanced attentional and mental rotation performance in A allele carriers supports recent findings that the A allele of this single nucleotide polymorphism (SNP) enhances cognitive performance on a general measure of cognitive processing speed.     

Event-related potential (ERP) asymmetries to emotional stimuli in a visual half-field paradigm

To investigate the hypothesis of a right hemispheric superiority in negative emotional processing, event-related potentials (ERPs) were recorded from 17 sites (Fz, Cz, Pz, F3/4, F7/8, C3/4, T7/8, P3/4, P7/8, O1/2) in a visual half-field paradigm. While maintaining fixation, right-handed women viewed pictures of patients with dermatological diseases before (negative) and after (neutral) cosmetic surgery. A principal components analysis with Varimax rotation performed on ERPs revealed factors identified as N1, N2, early P3, late P3, late P3, and slow wave. Repeated measures analyses of variance performed on factor scores revealed a significant effect of emotional content for all factors except for N1. However, asymmetries in emotional processing were restricted to N2 and early P3, with maximal effects over the right parietal region. N2–P3 amplitude was augmented for negative and reduced for neutral stimuli over right hemisphere regions. Visual field presentation interacted with these asymmetries in enhancing amplitudes contralaterally for early but ipsilaterally for late ERP components. Overall, findings for N2 and P3 support theories of an asymmetry in emotional processing.     

Auditory event-related potentials and alpha oscillations in the psychosis prodrome: Neuronal generator patterns during a novelty oddball task

Prior research suggests that event-related potentials (ERP) obtained during active and passive auditory paradigms, which have demonstrated abnormal neurocognitive function in schizophrenia, may provide helpful tools in predicting transition to psychosis. In addition to ERP measures, reduced modulations of EEG alpha, reflecting top-down control required to inhibit irrelevant information, have revealed attentional deficits in schizophrenia and its prodromal stage. Employing a three-stimulus novelty oddball task, nose-referenced 48-channel ERPs were recorded from 22 clinical high-risk (CHR) patients and 20 healthy controls detecting target tones (12% probability, 500 Hz; button press) among nontargets (76%, 350 Hz) and novel sounds (12%). After current source density (CSD) transformation of EEG epochs (− 200 to 1000 ms), event-related spectral perturbations were obtained for each site up to 30 Hz and 800 ms after stimulus onset, and simplified by unrestricted time–frequency (TF) principal components analysis (PCA). Alpha event-related desynchronization (ERD) as measured by TF factor 610–9 (spectral peak latency at 610 ms and 9 Hz; 31.9% variance) was prominent over right posterior regions for targets, and markedly reduced in CHR patients compared to controls, particularly in three patients who later developed psychosis. In contrast, low-frequency event-related synchronization (ERS) distinctly linked to novels (260–1; 16.0%; mid-frontal) and N1 sink across conditions (130–1; 3.4%; centro-temporoparietal) did not differ between groups. Analogous time-domain CSD-ERP measures (temporal PCA), consisting of N1 sink, novelty mismatch negativity (MMN), novelty vertex source, novelty P3, P3b, and frontal response negativity, were robust and closely comparable between groups. Novelty MMN at FCz was, however, absent in the three converters. In agreement with prior findings, alpha ERD and MMN may hold particular promise for predicting transition to psychosis among CHR patients.     

Interplay of neuronal processes during response inhibition: Results from a combined event-related potentials (ERPs)/transcranial magnetic stimulation (TMS) study on methylphenidate

The neuronal processes underlying response inhibition are often studied using either event-related potentials (ERPs) or by applying transcranial magnetic stimulation (TMS) to investigate excitatory and inhibitory processes in the motor system. We performed a more refined analysis of response inhibition by combining both approaches with the aim of identifying an interplay between ERPs and TMS parameters.During a go/nogo task, motor system excitability was measured using TMS single and double pulses and brain electrical activity was recorded in healthy adults (n = 14). Each participant completed two testing sessions, once on placebo and once on methylphenidate (double-blind, crossover design). Studying the effects of methylphenidate served as an example application for this combined approach.Developing regression models, inhibition-related TMS measures (e.g., short intracortical inhibition) and the contingent negative variation explained about 85% of the variance of the nogo-P3 under both MPH and placebo medication. The smaller the inhibitory effect in the motor system, the more terminal response control was required and the more resources were allocated for the evaluation of the inhibitory process, respectively, as indicated by a larger P3.Thus, an interplay between processes in the motor system (cortex) and control processes with sources in the prefrontal cortex and the anterior cingulate cortex (ACC) may take place, acting complementarily to facilitate a correct nogo-response.While ERPs rather represent initiation and monitoring of inhibitory processes and response control, motor inhibition may be best analyzed using TMS. A combined ERP/TMS analysis may allow for the development of distinct models concerning the interplay of processes involved in response inhibition.     

Dissociation of visual C1 and P1 components as a function of attentional load: An event-related potential study

The earliest cortical location at which attention influences visual processing is controversial. To address this issue, the C1 and P1 components of cue-elicited ERPs were examined in a spatially-cued task under high and low levels of attentional load (active vs. passive viewing). Cues were presented either to the left or to the right visual field in separate trials (unilateral presentation), or to both visual fields simultaneously (bilateral presentation). For the unilateral presentation, C1 (peak latency approximately 80 ms) was not modulated by attentional load, whereas P1 (peak latency approximately 120-140 ms) was larger for high-relative to low-load condition. Bilateral presentation of the stimuli enhanced the amplitude of the C1 component relative to unilateral presentation; however, the increase of signal/noise ratio of C1 revealed no attentional load effect on C1. Results show that attentional load modulates visual processing in the P1, but not in the C1 time range, regardless of the increased signal/noise ratio by bilateral presentation. While it remains unclear about the conditions under which a C1 attentional effect is reliably elicited, the present results suggest that the direct manipulation of attentional load under a voluntary attention task seems not crucial for eliciting C1 attentional effect.     

Mokken scaling and principal components analyses of the CORE‐OM in a large clinical sample

In a sample of 543 adult National Health Service (NHS) patients referred to a Psychological Therapies Service, the responses to the Clinical Outcomes in Routine Evaluation‐Outcome Measure (CORE‐OM) self‐report questionnaire were examined using conventional principal components analysis (PCA) and a unique application of Mokken Scaling Procedure (MSP). Following the theoretical views of G. A. Foulds, it was suggested that some items more properly belong to the universe of attitudes and traits rather than that of symptoms and states. Accordingly, the analyses were carried out both with and without the CORE‐OM Risk domain items. Both PCAs produced a very large first component of Psychological distress, while the small second component differs. With all items included, the second component was of Risk. With the risk items excluded, the second component was now Functioning. The MSP results, respectively, were of a five‐item scale of Functioning (impaired by depression) and on the second analysis, a five‐item Functioning scale (impaired by anxiety). There was discussion on the criteria for item selection, the time scale specified in questionnaire instructions and the optimum number of items required for a symptom scale. It was concluded that the CORE‐OM item pool did not conform to its purported face validity domains and subdomains, but predominantly constitutes a large Psychological distress scale with considerable item redundancy. Copyright © 2009 John Wiley & Sons, Ltd.     

Sequential processing in the classic oddball task: ERP components,probability, and behavior

This study compared the ERP components and behavior associated with the auditory equiprobable and classic oddball tasks, to relate the cognitive processing stages in those paradigms and continue the development of the sequential processing schema. Target and nontarget ERP data were acquired from 66 healthy young adults (M_age = 20.1, SD = 2.4 years, 14 male) who completed both equiprobable (target p = 0.5) and oddball tasks (target p = 0.3). Separate temporal PCAs were used to decompose the ERP data in each task and condition, and the similarity of the components identified in each condition was examined between tasks. Probability effects on component amplitudes and behavior were also analyzed to identify task differences in cognitive demands. A highly similar series of components was identified in each task, closely matching the schema: targets elicited N1‐3, N1‐1, PN, N2c, P3b, SW1, SW2; whereas nontargets elicited N1‐3, N1‐1, PN, N2b, P3a, SW1, SW2. N1‐1 and PN amplitudes increased as stimulus probability decreased, irrespective of the condition. N2b, P3b, SW1, and SW2 amplitudes also varied between tasks, illustrating task‐specific demands on those processing stages. These findings complemented the behavioral outcomes, which demonstrated greater accuracy and control in the classic oddball task. Overall, this study demonstrated comparable processing in the auditory equiprobable and classic oddball tasks, extending the generalizability of the schema and enabling further integration of the ERP theory associated with these tasks. This study also clarifies stimulus probability effects on the schema, providing important insight into the functionality of common ERP components.     

Influence of task difficulty on the features of event-related potential during visual oddball task

We present a comprehensive analysis of the change in event-related potential (ERP) due to task difficulty during a visual oddball task. Specifically, we investigated the inter-subject difference in difficulty-related change of ERP patterns using single-trial ERP analysis focusing on P300 and P2 components. ERPs were recorded and analyzed from 14 subjects while performing a visual oddball task with two difficulty levels. After extracting independent components (ICs) from single-trial ERPs, the averaged ERPs were used to identify which ICs originated from major ERP components. The ERP components were estimated from single-trial waveforms by back-projecting relevant ICs onto scalp electrodes after removing all other ICs; thus, the comparison of ERP components could be performed for each subject. The averaged P300 amplitude was smaller and latency was larger for the more difficult task, and this tendency was also observed for single-trial ERP analysis within each subject. P2 amplitude increased for the hard task for both group and individual analyses, suggesting that the P2 may be interpreted as a manifestation of task relevance evaluation or response generation. The P2 amplitude and latency were more notably correlated with response time for the more difficult task.