Event-related potentials of the brain and cognitive processes: approaches and applications

Theta oscillations underlie the interplay between emotional processing and empathy

Emotional reactions to salient stimuli are well documented in psychophysiological research. However, some individual variables that can influence how people process emotions (i.e., empathy traits) have received little consideration. The present study investigated the relationship between emotions and empathy. Forty participants completed the Interpersonal Reactivity Index, a questionnaire that measure general and specific empathy dimensions. Then, emotional (erotic and mutilation) and non-emotional pictures were presented, during electroencephalographic recording. Valence and arousal were evaluated for each stimulus. Behavioral results revealed a positive correlation between the arousal induced by mutilation pictures and personal distress (i.e., feeling discomfort in emergency situations). At the electrophysiological level, theta activity elicited by positive and negative emotion processing in the superior frontal gyrus was associated with personal distress. Moreover, erotic-related theta in the middle frontal gyrus was associated with subjective judgement of erotic stimulus valence. Overall, theta activity modulated the interplay between emotions and empathy.

Electrophysiological indexes for impaired response inhibition and salience attribution in substance (stimulants and depressants) use disorders: A meta-analysis

The impairment of inhibitory control and reward system is the core feature underlying substance use disorder (SUD). Previous studies suggested that it can be regarded as impaired response inhibition and salience attribution syndrome (iRISA). The neural substrates of the two deficit functions were widely investigated in neuroimaging studies, and the impaired prefrontal cortex, limbic-orbitofrontal network, and fronto-insular-parietal network were observed. Previous Event-related potential (ERP) studies were also conducted to explore EEG indexes related to abnormal brain function. In the current meta-analysis, we aimed to explore the consistency of ERP indexes that can reflect the two aberrant processes: P300/slow potential (SP) for salience attribution and Error-related negativity (ERN)/Nogo-N200/Nogo-P300 for inhibitory control and conflict monitoring. Subgroup analyses for drug type and drug use conditions were also conducted. According to the 60 research studies, we found significantly enhanced drug-cue-induced P300 amplitude and attenuated Nogo-N200 amplitude in SUD individuals relative to Healthy control (HC), which supports the dual model. Moreover, the drug-cue-induced P300 displayed time-dependence recovery, suggesting a potential index for treatment evaluation. In conclusion, drug-cue-induced P300 and Nogo-N200 demonstrated high consistency, and the drug-cue-induced P300 can be used to track the changes of functional recovery for SUD. The integration of the two ERP components could be regarded as a potential biomarker for SUD, which may provide a new insight for clinical treatment and investigation.

EEG Spatiotemporal Patterns Underlying Self-other Voice Discrimination

There is growing evidence showing that the representation of the human “self” recruits special systems across different functions and modalities. Compared to self-face and self-body representations, few studies have investigated neural underpinnings specific to self-voice. Moreover, self-voice stimuli in those studies were consistently presented through air and lacking bone conduction, rendering the sound of self-voice stimuli different to the self-voice heard during natural speech. Here, we combined psychophysics, voice-morphing technology, and high-density EEG in order to identify the spatiotemporal patterns underlying self-other voice discrimination (SOVD) in a population of 26 healthy participants, both with air- and bone-conducted stimuli. We identified a self-voice-specific EEG topographic map occurring around 345 ms post-stimulus and activating a network involving insula, cingulate cortex, and medial temporal lobe structures. Occurrence of this map was modulated both with SOVD task performance and bone conduction. Specifically, the better participants performed at SOVD task, the less frequently they activated this network. In addition, the same network was recruited less frequently with bone conduction, which, accordingly, increased the SOVD task performance. This work could have an important clinical impact. Indeed, it reveals neural correlates of SOVD impairments, believed to account for auditory-verbal hallucinations, a common and highly distressing psychiatric symptom.

Probing regional cortical excitability via input-output properties using transcranial magnetic stimulation and electroencephalography coupling

The modular organization of the cortex refers to subsets of highly interconnected nodes, sharing specific cytoarchitectural and dynamical properties. These properties condition the level of excitability of local pools of neurons. In this study, we described TMS evoked potentials (TEP) input-output properties to provide new insights into regional cortical excitability. We combined robotized TMS with EEG to disentangle region-specific TEP from threshold to saturation and describe their oscillatory contents. Twenty-two young healthy participants received robotized TMS pulses over the right primary motor cortex (M1), the right dorsolateral prefrontal cortex (DLPFC) and the right superior occipital lobe (SOL) at five stimulation intensities (40, 60, 80, 100, and 120% resting motor threshold) and one short-interval intracortical inhibition condition during EEG recordings. Ten additional subjects underwent the same experiment with a realistic sham TMS procedure. The results revealed interregional differences in the TEPs input-output functions as well as in the responses to paired-pulse conditioning protocols, when considering early local components (<80 ms). Each intensity in the three regions was associated with complex patterns of oscillatory activities. The quality of the regression of TEPs over stimulation intensity was used to derive a new readout for cortical excitability and dynamical properties, revealing lower excitability in the DLPFC, followed by SOL and M1. The realistic sham experiment confirmed that these early local components were not contaminated by multisensory stimulations. This study provides an entirely new analytic framework to characterize input-output relations throughout the cortex, paving the way to a more accurate definition of local cortical excitability.

Spectral fingerprints of correct vestibular discrimination of the intensity of body accelerations

Perceptual decision-making is a complex task that requires multiple processing steps performed by spatially distinct brain regions interacting in order to optimize perception and motor response. Most of our knowledge on these processes and interactions were derived from unimodal stimulations of the visual system which identified the lateral intraparietal area and the posterior parietal cortex as critical regions. Unlike the visual system, the vestibular system has no primary cortical areas and it is associated with separate multisensory areas within the temporo-parietal cortex with the parieto-insular vestibular cortex, PIVC, being the core region. The aim of the presented experiment was to investigate the transition from sensation to perception and to reveal the main structures of the cortical vestibular system involved in perceptual decision-making. Therefore, an EEG analysis was performed in 35 healthy subjects during linear whole-body accelerations of different intensities on a motor-driven motion platform (hexapod). We used a discrimination task in order to judge the intensity of the accelerations. Furthermore, we manipulated the expectation of the upcoming stimulus by indicating the probability (25%, 50%, 75%, 100%) of the motion direction. The analysis of the vestibular evoked potentials (VestEPs) showed that the decision-making process leads to a second positive peak (P2b) which was not observed in previous task-free experiments. The comparison of the estimated neural generators of the P2a and P2b components showed significant activity differences in the anterior cingulus, the parahippocampal and the middle temporal gyri. Taking into account the time courses of the P2 components, the physical properties of the stimuli, and the responses given by the subjects we conclude that the P2b likely reflects the transition from the processing of sensory information to perceptual evaluation. Analyzing the decision-uncertainty reported by the subjects, a persistent divergence of the time courses starting at 188 ​ms after the acceleration was found at electrode Pz. This finding demonstrated that meta-cognition by means of confidence estimation starts in parallel with the decision-making process itself. Further analyses in the time-frequency domain revealed that a correct classification of acceleration intensities correlated with an inter-trial phase clustering at electrode Cz and an inter-site phase clustering of theta oscillations over frontal, central, and parietal cortical areas. The sites where the phase clustering was observed corresponded to core decision-making brain areas known from neuroimaging studies in the visual domain.

Adaptações do cérebro durante uma tarefa de longa duração: Um estudo de Potencial Relacionado a Evento

Resumo O objetivo deste estudo é investigar o efeito da demanda cognitiva prolongada na modulação do Potencial Relacionado a Evento (ERP) em um paradigma de controle inibitório. Os dados foram coletados em 19 voluntários destros, com a média de idade de 21,21 (±1,77) anos, que realizaram o paradigma do Go/NoGo durante 50 minutos, com gravação sincronizada do eletroencefalograma para obtenção dos ERPs. O efeito do tempo de realização da tarefa provocou alterações significativas nas variáveis subjetivas, de desempenho cognitivo e nas amplitudes máximas dos componentes N2 e P3. Nossos resultados sugerem que quando nosso cérebro está submetido a demandas cognitivas extensas, ocorrem adaptações para a manutenção do desempenho comportamental através da estratégia de realocação de recursos energéticos.

Early sensitivity of evoked potentials to surface and volumetric structure during the visual perception of three-dimensional object shape

This study used event-related potentials (ERPs) to elucidate how the human visual system processes three-dimensional (3-D) object shape structure. In particular, we examined whether the perceptual mechanisms that support the analysis of 3-D shape are differentially sensitive to higher order surface and volumetric part structure. Observers performed a whole-part novel object matching task in which part stimuli comprised sub-regions of closed edge contour, surfaces or volumetric parts. Behavioural response latency data showed an advantage in matching surfaces and volumetric parts to whole objects over contours, but no difference between surfaces and volumes. ERPs were analysed using a convergence of approaches based on stimulus dependent amplitude modulations of evoked potentials, topographic segmentation, and spatial frequency oscillations. The results showed early differential perceptual processing of contours, surfaces, and volumetric part stimuli. This was first reliably observed over occipitoparietal electrodes during the N1 (140-200 ms) with a mean peak latency of 170 ms, and continued on subsequent P2 (220-260 ms) and N2 (260-320 ms) components. The differential sensitivity in perceptual processing during the N1 was accompanied by distinct microstate patterns that distinguished among contours, surfaces and volumes, and predominant theta band activity around 4-7 Hz over right occipitoparietal and orbitofrontal sites. These results provide the first evidence of early differential perceptual processing of higher order surface and volumetric shape structure within the first 200 ms of stimulus processing. The findings challenge theoretical models of object recognition that do not attribute functional significance to surface and volumetric object structure during visual perception.

Robust and Gaussian spatial functional regression models for analysis of event-related potentials

Event-related potentials (ERPs) summarize electrophysiological brain response to specific stimuli. They can be considered as correlated functions of time with both spatial correlation across electrodes and nested correlations within subjects. Commonly used analytical methods for ERPs often focus on pre-determined extracted components and/or ignore the correlation among electrodes or subjects, which can miss important insights, and tend to be sensitive to outlying subjects, time points or electrodes. Motivated by ERP data in a smoking cessation study, we introduce a Bayesian spatial functional regression framework that models the entire ERPs as spatially correlated functional responses and the stimulus types as covariates. This novel framework relies on mixed models to characterize the effects of stimuli while simultaneously accounting for the multilevel correlation structure. The spatial correlation among the ERP profiles is captured through basis-space Matérn assumptions that allow either separable or nonseparable spatial correlations over time. We induce both adaptive regularization over time and spatial smoothness across electrodes via a correlated normal-exponential-gamma (CNEG) prior on the fixed effect coefficient functions. Our proposed framework includes both Gaussian models as well as robust models using heavier-tailed distributions to make the regression automatically robust to outliers. We introduce predictive methods to select among Gaussian vs. robust models and models with separable vs. non-separable spatiotemporal correlation structures. Our proposed analysis produces global tests for stimuli effects across entire time (or time-frequency) and electrode domains, plus multiplicity-adjusted pointwise inference based on experiment-wise error rate or false discovery rate to flag spatiotemporal (or spatio-temporal-frequency) regions that characterize stimuli differences, and can also produce inference for any prespecified waveform components. Our analysis of the smoking cessation ERP data set reveals numerous effects across different types of visual stimuli.

Association of Preterm Birth With Attention-Deficit/Hyperactivity Disorder-Like and Wider-Ranging Neurophysiological Impairments of Attention and Inhibition

OBJECTIVE

Preterm birth has been associated with an increased risk of attention-deficit/hyperactivity disorder (ADHD)-like symptoms and cognitive impairments similar to those seen in ADHD, including attention and inhibitory control difficulties. Yet data on direct comparisons across ADHD and preterm birth on cognitive-neurophysiological measures are limited.

METHOD

We directly compared 186 preterm-born adolescents to 69 term-born adolescents with ADHD and 135 term-born controls on cognitive-performance and event-related potential measures associated with attentional and inhibitory processing from a cued continuous performance test (CPT-OX), which we have previously shown to discriminate between the adolescents with ADHD and controls. We aimed to elucidate whether the ADHD-like symptoms and cognitive impairments in preterm-born individuals reflect identical cognitive-neurophysiological impairments in term-born individuals with ADHD.

RESULTS

Go-P3 amplitude was reduced, reflecting impaired executive response control, in preterm-born adolescents compared to both controls and adolescents with ADHD. Moreover, in preterm-born adolescents, as in term-born adolescents with ADHD, contingent negative variation amplitude was attenuated, reflecting impairments in response preparation compared to controls. Although the ADHD group showed significantly increased NoGo-P3 amplitude at FCz compared to preterm group, at Cz preterm-born adolescents demonstrated significantly decreased NoGo-P3 amplitude compared to the control group, similar to term-born adolescents with ADHD.

CONCLUSION

These findings indicate impairments in response preparation, executive response control, and response inhibition in preterm-born adolescents. Although the response preparation and response inhibition impairments found in preterm-born adolescents overlap with those found in term-born adolescents with ADHD, the preterm group also shows unique impairments, suggesting more wide-ranging impairments in the preterm group compared to the ADHD group.

Increased electroencephalographic activity in crack-cocaine users visualizing crack cues

This study aimed to examine electrophysiologically the cerebral function under visual cue-reactivity paradigm in crack-cocaine users. This was an exploratory open trial in which young crack-cocaine-users and non-users were clinically examined. The participants' brain activity was analyzed by an event-related potentials procedure under a cue-reactivity paradigm with the random visual presentation of crack-related and neutral images. Nine young male crack-cocaine users and nine age-matched male healthy subjects from research center's neighborhood volunteered themselves to participate in this study. We demonstrated through electrophysiological tools that crack-cocaine users are more likely to show higher brain activity, notably in the frontal lobe region, when processing crack-related images. Though imaging studies have already showed increased brain activity in this paradigm, this data shows that event-related potentials can be an effective tool for brain evaluation in addiction.

Neural initialization of audiovisual integration in prereaders at varying risk for developmental dyslexia

Learning letter-speech sound correspondences is a major step in reading acquisition and is severely impaired in children with dyslexia. Up to now, it remains largely unknown how quickly neural networks adopt specific functions during audiovisual integration of linguistic information when prereading children learn letter-speech sound correspondences. Here, we simulated the process of learning letter-speech sound correspondences in 20 prereading children (6.13-7.17 years) at varying risk for dyslexia by training artificial letter-speech sound correspondences within a single experimental session. Subsequently, we acquired simultaneously event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) scans during implicit audiovisual presentation of trained and untrained pairs. Audiovisual integration of trained pairs correlated with individual learning rates in right superior temporal, left inferior temporal, and bilateral parietal areas and with phonological awareness in left temporal areas. In correspondence, a differential left-lateralized parietooccipitotemporal ERP at 400 ms for trained pairs correlated with learning achievement and familial risk. Finally, a late (650 ms) posterior negativity indicating audiovisual congruency of trained pairs was associated with increased fMRI activation in the left occipital cortex. Taken together, a short (<30 min) letter-speech sound training initializes audiovisual integration in neural systems that are responsible for processing linguistic information in proficient readers. To conclude, the ability to learn grapheme-phoneme correspondences, the familial history of reading disability, and phonological awareness of prereading children account for the degree of audiovisual integration in a distributed brain network. Such findings on emerging linguistic audiovisual integration could allow for distinguishing between children with typical and atypical reading development. Hum Brain Mapp 38:1038-1055, 2017. © 2016 Wiley Periodicals, Inc.

Whole-scalp EEG mapping of somatosensory evoked potentials in macaque monkeys

High-density scalp EEG recordings are widely used to study whole-brain neuronal networks in humans non-invasively. Here, we validate EEG mapping of somatosensory evoked potentials (SSEPs) in macaque monkeys (Macaca fascicularis) for the long-term investigation of large-scale neuronal networks and their reorganisation after lesions requiring a craniotomy. SSEPs were acquired from 33 scalp electrodes in five adult anaesthetized animals after electrical median or tibial nerve stimulation. SSEP scalp potential maps were identified by cluster analysis and identified in individual recordings. A distributed, linear inverse solution was used to estimate the intracortical sources of the scalp potentials. SSEPs were characterised by a sequence of components with unique scalp topographies. Source analysis confirmed that median nerve SSEP component maps were in accordance with the somatotopic organisation of the sensorimotor cortex. Most importantly, SSEP recordings were stable both intra- and interindividually. We aim to apply this method to the study of recovery and reorganisation of large-scale neuronal networks following a focal cortical lesion requiring a craniotomy. As a prerequisite, the present study demonstrated that a 300-mm² unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs. In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion.

EEG source imaging of brain states using spatiotemporal regression

Relating measures of electroencephalography (EEG) back to the underlying sources is a long-standing inverse problem. Here we propose a new method to estimate the EEG sources of identified electrophysiological states that represent spontaneous activity, or are evoked by a stimulus, or caused by disease or disorder. Our method has the unique advantage of seamlessly integrating a statistical significance of the source estimate while efficiently eliminating artifacts (e.g., due to eye blinks, eye movements, bad electrodes). After determining the electrophysiological states in terms of stable topographies using established methods (e.g.: ICA, PCA, k-means, epoch average), we propose to estimate these states' time courses through spatial regression of a General Linear Model (GLM). These time courses are then used to find EEG sources that have a similar time-course (using temporal regression of a second GLM). We validate our method using both simulated and experimental data. Simulated data allows us to assess the difference between source maps obtained by the proposed method and those obtained by applying conventional source imaging of the state topographies. Moreover, we use data from 7 epileptic patients (9 distinct epileptic foci localized by intracranial EEG) and 2 healthy subjects performing an eyes-open/eyes-closed task to elicit activity in the alpha frequency range. Our results indicate that the proposed EEG source imaging method accurately localizes the sources for each of the electrical brain states. Furthermore, our method is particularly suited for estimating the sources of EEG resting states or otherwise weak spontaneous activity states, a problem not adequately solved before.

Unravelling developmental disregard in children with unilateral cerebral palsy by measuring event-related potentials during a simple and complex task

BACKGROUND

In a subset of children with unilateral Cerebral Palsy (CP) a discrepancy between capacity and performance of the affected upper limb can be observed. This discrepancy is known as Developmental Disregard (DD). Though the phenomenon of DD has been well documented, its underlying cause is still under debate. DD has originally been explained based on principles of operant conditioning. Alternatively, it has been proposed that DD results from a diminished automaticity of movements, resulting in an increased cognitive load when using the affected hand. To investigate the amount of involved cognitive load we studied Event-Related Potentials (ERPs) preceding task-related motor responses during a single-hand capacity and a dual-hand performance task. It was hypothesised that children with DD show alterations related to long-latency ERP components when selecting a response with the affected upper limb, reflecting increased cognitive load in order to generate an adequate response and especially so within the dual-hand task.

METHODS

Fifteen children with unilateral CP participated in the study. One of the participants was excluded due to major visual impairments. Seven of the remaining participants displayed DD. The other seven children served as a control group. All participants performed two versions of a cue-target paradigm, a single-hand capacity and a dual-hand performance task. The ERP components linked to target presentation were inspected: the mid-latency P2 component and the consecutive long-latency N2b component.

RESULTS

In the dual-hand performance task children with DD showed an enhancement in mean amplitude of the long-latency N2b component when selecting a response with their affected hand. No differences were found regarding the amplitude of the mid-latency P2 component. No differences were observed regarding the single-hand capacity task. The control group did not display any differences in ERPs linked to target evaluation processes between both hands.

CONCLUSION

These electrophysiological findings show that DD is associated with increased cognitive load when movements are prepared with the affected hand during a dual-hand performance task. These findings confirm behavioural observations, advance our insights on the neural substrate of DD and have implications for therapy.

Improved characterization of visual evoked potentials in multiple sclerosis by topographic analysis

In multiple sclerosis (MS), the combination of visual, somatosensory and motor evoked potentials (EP) has been shown to be highly correlated with the Expanded Disability Severity Scale (EDSS) and to predict the disease course. In the present study, we explored whether the significance of the visual EP (VEP) can be improved with multichannel recordings (204 electrodes) and topographic analysis (tVEP). VEPs were analyzed in 83 MS patients (median EDSS 2.0; 52 % with history of optic neuritis; hON) and 47 healthy controls (HC). TVEP components were automatically defined on the basis of spatial similarity between the scalp potential fields (topographic maps) of single subjects’ VEPs and reference maps generated from HC. Non-ambiguous measures of latency, amplitude and configuration were derived from the maps reflecting the P100 component. TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves. In tVEP, reliability tended to be higher for measurement of amplitude (p = 0.06). Regression models on diagnosis (MS vs. HC) and hON were more favorable using tVEP- versus cVEP-predictors. Sensitivity was increased in tVEP versus cVEP: 72 % versus 60 % for diagnosis, and 88 % versus 77 % for hON. The advantage of tVEP was most pronounced in pathological VEPs, in which cVEPs were often ambiguous. TVEP is a reliable, valid, and sensitive method of objectively quantifying pathological VEP in particular. In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

Control-display mapping in brain-computer interfaces

Event-related potential (ERP) based brain-computer interfaces (BCIs) employ differences in brain responses to attended and ignored stimuli. When using a tactile ERP-BCI for navigation, mapping is required between navigation directions on a visual display and unambiguously corresponding tactile stimuli (tactors) from a tactile control device: control-display mapping (CDM). We investigated the effect of congruent (both display and control horizontal or both vertical) and incongruent (vertical display, horizontal control) CDMs on task performance, the ERP and potential BCI performance. Ten participants attended to a target (determined via CDM), in a stream of sequentially vibrating tactors. We show that congruent CDM yields best task performance, enhanced the P300 and results in increased estimated BCI performance. This suggests a reduced availability of attentional resources when operating an ERP-BCI with incongruent CDM. Additionally, we found an enhanced N2 for incongruent CDM, which indicates a conflict between visual display and tactile control orientations.

PRACTITIONER SUMMARY

Incongruency in control-display mapping reduces task performance. In this study, brain responses, task and system performance are related to (in)congruent mapping of command options and the corresponding stimuli in a brain-computer interface (BCI). Directional congruency reduces task errors, increases available attentional resources, improves BCI performance and thus facilitates human-computer interaction.

Role of basal ganglia circuits in resisting interference by distracters: a swLORETA study

Background

The selection of task-relevant information requires both the focalization of attention on the task and resistance to interference from irrelevant stimuli. Both mechanisms rely on a dorsal frontoparietal network, while focalization additionally involves a ventral frontoparietal network. The role of subcortical structures in attention is less clear, despite the fact that the striatum interacts significantly with the frontal cortex via frontostriatal loops. One means of investigating the basal ganglia's contributions to attention is to examine the features of P300 components (i.e. amplitude, latency, and generators) in patients with basal ganglia damage (such as in Parkinson's disease (PD), in which attention is often impaired). Three-stimulus oddball paradigms can be used to study distracter-elicited and target-elicited P300 subcomponents.

Methodology/Principal Findings

In order to compare distracter- and target-elicited P300 components, high-density (128-channel) electroencephalograms were recorded during a three-stimulus visual oddball paradigm in 15 patients with early PD and 15 matched healthy controls. For each subject, the P300 sources were localized using standardized weighted low-resolution electromagnetic tomography (swLORETA). Comparative analyses (one-sample and two-sample t-tests) were performed using SPM5® software. The swLORETA analyses showed that PD patients displayed fewer dorsolateral prefrontal (DLPF) distracter-P300 generators but no significant differences in target-elicited P300 sources; this suggests dysfunction of the DLPF cortex when the executive frontostriatal loop is disrupted by basal ganglia damage.

Conclusions/Significance

Our results suggest that the cortical attention frontoparietal networks (mainly the dorsal one) are modulated by the basal ganglia. Disruption of this network in PD impairs resistance to distracters, which results in attention disorders.

Face-sensitive processes one hundred milliseconds after picture onset

The human face is the most studied object category in visual neuroscience. In a quest for markers of face processing, event-related potential (ERP) studies have debated whether two peaks of activity – P1 and N170 – are category-selective. Whilst most studies have used photographs of unaltered images of faces, others have used cropped faces in an attempt to reduce the influence of features surrounding the “face–object” sensu stricto. However, results from studies comparing cropped faces with unaltered objects from other categories are inconsistent with results from studies comparing whole faces and objects. Here, we recorded ERPs elicited by full front views of faces and cars, either unaltered or cropped. We found that cropping artificially enhanced the N170 whereas it did not significantly modulate P1. In a second experiment, we compared faces and butterflies, either unaltered or cropped, matched for size and luminance across conditions, and within a narrow contrast bracket. Results of Experiment 2 replicated the main findings of Experiment 1. We then used face–car morphs in a third experiment to manipulate the perceived face-likeness of stimuli (100% face, 70% face and 30% car, 30% face and 70% car, or 100% car) and the N170 failed to differentiate between faces and cars. Critically, in all three experiments, P1 amplitude was modulated in a face-sensitive fashion independent of cropping or morphing. Therefore, P1 is a reliable event sensitive to face processing as early as 100 ms after picture onset.

Attentional modulation of early ERP components in response to faces: evidence from the attentional blink paradigm

The attentional blink (AB) is a transient attentional deficit that occurs when two stimuli that must both be detected are presented within an interval of less than 500 ms. Event-related potential (ERP) investigations have suggested that the AB affects a specific component, the P3, which is suppressed when targets are blinked. In view of the link between the P3 and working memory, it has been suggested that the AB might be due to the inability of the blinked target to access working memory. Interestingly, it seems that faces, due to their saliency, might escape the AB effect when cross-category detection is required (i.e., when the targets are composed of faces versus other categories of stimuli). In the present study we investigated this phenomenon in an event-related potential (ERP) study using upright and inverted faces as targets. In a first task, the participants were asked to identify two successive targets, the first composed of geometric shapes and the second of upright or inverted faces. A second control task, identical to the first was also performed, in which only the second targets had to be identified in order to compare ERPs. ERPs and scalp topographies of physically identical sequences of events, differing only by the attentional involvement, were thus compared. Behavioural results showed that faces indeed escape the AB while inverted faces do not. However, the electrophysiological findings showed that when attention was engaged in a previous stimulus (at the shortest lag times), both upright and inverted faces showed a decreased amplitude in the 150-260 ms time period, in addition to a lower P3. At longer lags, when the AB was no longer observed, no ERP differences were found. Our data demonstrate that, although faces escape the attentional blink, previous attentional involvement occurs much earlier than described for other categories of stimuli. This suggests that faces are subjected to an early selection which might allow rapid re-allocation of attention to the stimulus if it is deemed meaningful.

Cognitive-electrophysiological indices of attentional and inhibitory processing in adults with ADHD: familial effects

Background

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. In a comparison of adults with ADHD and a matched control sample, we previously showed that abnormal inhibitory processing is typically preceded or accompanied by other processing deficits in adult ADHD. We now compare these data further to additional data from first-degree relatives (fathers) of children with ADHD to identify whether this pattern of abnormal processing shares familial influences with ADHD in adults.

Methods

Using a family design, we compared 20 fathers of children with the combined subtype of ADHD with 21 adults with ADHD combined subtype and 20 controls in event-related potential indices of preparatory states and subsequent response inhibition processing as elicited by a cued continuous performance task.

Results

Fathers of children with ADHD exhibited significantly weaker orienting attention to cues and inhibitory processing than the controls but not the ADHD sample.

Conclusions

These findings provide evidence for the familial association of attentional orienting and response inhibition processes with ADHD in adults and indicate a familial and neurobiological link between ADHD in children and adults.

Electrophysiological evidence for impaired attentional engagement with phonologically acceptable misspellings in developmental dyslexia

Event-related potential (ERP) studies of word recognition have provided fundamental insights into the time-course and stages of visual and auditory word form processing in reading. Here, we used ERPs to track the time-course of phonological processing in dyslexic adults and matched controls. Participants engaged in semantic judgments of visually presented high-cloze probability sentences ending either with (a) their best completion word, (b) a homophone of the best completion, (c) a pseudohomophone of the best completion, or (d) an unrelated word, to examine the interplay of phonological and orthographic processing in reading and the stage(s) of processing affected in developmental dyslexia. Early ERP peaks (N1, P2, N2) were modulated in amplitude similarly in the two groups of participants. However, dyslexic readers failed to show the P3a modulation seen in control participants for unexpected homophones and pseudohomophones (i.e., sentence completions that are acceptable phonologically but are misspelt). Furthermore, P3a amplitudes significantly correlated with reaction times in each experimental condition. Our results showed no sign of a deficit in accessing phonological representations during reading, since sentence primes yielded phonological priming effects that did not differ between participant groups in the early phases of processing. On the other hand, we report new evidence for a deficient attentional engagement with orthographically unexpected but phonologically expected words in dyslexia, irrespective of task focus on orthography or phonology. In our view, this result is consistent with deficiency in reading occurring from the point at which attention is oriented to phonological analysis, which may underlie broader difficulties in sublexical decoding.

Use of swLORETA to localize the cortical sources of target- and distracter-elicited P300 components

OBJECTIVE

Cognitive event-related potentials (especially P300) have long been used to explore attentional processes. The aim of this study was to identify the cortical areas involved in P300 generation during a selective attention task.

METHODS

128 channel electroencephalograms were recorded in 15 healthy controls performing a three-stimulus visual oddball paradigm, in order to identify distracter- and target-elicited P300 components. For each subject, the P300 sources were localized using standardized weighted low-resolution electromagnetic tomography (swLORETA). One sample and paired T-tests were performed using SPM5®.

RESULTS

Common sources for both P300 components were observed within a large frontoparietal network, including the frontal eye field and dorsal parietal cortex (i.e. the attentional dorsal frontoparietal network). More inferior parietal areas, prefrontal and cingulate cortices (i.e. the attentional ventral frontoparietal network) were also involved in the generation of target-elicited P300.

CONCLUSIONS

These results suggest that distracter- and target-elicited P300 are both generated by the dorsal frontoparietal network. Moreover, target processing recruits a specific ventral network.

SIGNIFICANCE

Our data agree with the literature reports using other methods and should help to improve our knowledge of the cerebral networks underlying attentional processes.

Schizotypal perceptual aberrations of time: correlation between score, behavior and brain activity

A fundamental trait of the human self is its continuum experience of space and time. Perceptual aberrations of this spatial and temporal continuity is a major characteristic of schizophrenia spectrum disturbances – including schizophrenia, schizotypal personality disorder and schizotypy. We have previously found the classical Perceptual Aberration Scale (PAS) scores, related to body and space, to be positively correlated with both behavior and temporo-parietal activation in healthy participants performing a task involving self-projection in space. However, not much is known about the relationship between temporal perceptual aberration, behavior and brain activity. To this aim, we composed a temporal Perceptual Aberration Scale (tPAS) similar to the traditional PAS. Testing on 170 participants suggested similar performance for PAS and tPAS. We then correlated tPAS and PAS scores to participants' performance and neural activity in a task of self-projection in time. tPAS scores correlated positively with reaction times across task conditions, as did PAS scores. Evoked potential mapping and electrical neuroimaging showed self-projection in time to recruit a network of brain regions at the left anterior temporal cortex, right temporo-parietal junction, and occipito-temporal cortex, and duration of activation in this network positively correlated with tPAS and PAS scores. These data demonstrate that schizotypal perceptual aberrations of both time and space, as reflected by tPAS and PAS scores, are positively correlated with performance and brain activation during self-projection in time in healthy individuals along the schizophrenia spectrum.

[The significance of functional psychophysiological methods in child and adolescent psychiatry]

Psychophysiological research focusing on child development and on child and adolescent psychiatric disorders has provided many important insights. The use of cognitive neuroscience methods along with the assessment of peripheral psychophysiological measures - particularly functional magnetic resonance imaging and electroencephalography reflecting brain activity - have advanced our understanding of the physiological basis of many cognitive processes such as attention, memory, learning, and language in the context of child development and psychiatric disorders. These insights are proving increasingly helpful when evaluating and advancing treatment. The following review introduces the reader to psychophysiological and particularly electrophysiological methods widely used in child and adolescent psychiatry research.

Electrophysiological evidence for abnormal preparatory states and inhibitory processing in adult ADHD

Background

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. Several theories postulate deficits in ADHD that have effects across many executive functions or in more narrowly defined aspects, such as response inhibition. Electrophysiological studies on children, however, indicate that ADHD is not associated with a core deficit of response inhibition, as abnormal inhibitory processing is typically preceded or accompanied by other processing deficits. It is not yet known if this pattern of abnormal processing is evident in adult ADHD.

Methods

The objective of this paper was to investigate event-related potential indices of preparatory states and subsequent response inhibition processing in adults with ADHD. Two cued continuous performance tasks were presented to 21 adults meeting current criteria for adult ADHD and combined type ADHD in childhood, and 20 controls.

Results

The ADHD group exhibited significantly weaker orienting attention to cues, cognitive preparation processes and inhibitory processing. In addition, we observed a strong correlation between the resources allocated to orienting to cues and the strength of the subsequent response strength control processes, suggesting that orienting deficits partly predict and determine response control deficits in ADHD.

Conclusions

These findings closely resemble those previously found in children with ADHD, which indicate that there is not a core response inhibition deficit in ADHD. These findings therefore suggest the possibility of developmental stability into adulthood of the underlying abnormal processes in ADHD.

Development of visual expertise for reading: rapid emergence of visual familiarity for an artificial script

Adults produce left-lateralized N170 responses to visual words relative to control stimuli, even within tasks that do not require active reading. This specialization begins in preschoolers as a right-lateralized N170 effect. We investigated whether this developmental shift reflects an early learning phenomenon, such as attaining visual familiarity with a script, by training adults in an artificial script and measuring N170 responses before and afterward. Training enhanced the N170 response, especially over the right hemisphere. This suggests N170 sensitivity to visual familiarity with a script emerges before reading becomes sufficiently automatic to drive left-lateralized effects in a shallow encoding task.

Mental imagery of self-location during spontaneous and active self-other interactions: an electrical neuroimaging study

Substantial data from the cognitive neurosciences point to the importance of bodily processing for the development of a comprehensive theory of the self. A key aspect of the bodily self is self-location, the experience that the self is localized at a specific position in space within one's bodily borders (embodied self-location). Although the neural mechanisms of self-location have been studied by manipulating the spatial location of one's visual perspective during mental imagery, such experiments were conducted in constrained, explicit, and unecological contexts such as explicit instructions in a prone/seated position, although most human interactions occur spontaneously while standing/walking. Using a motor paradigm, we investigated the behavioral and neural mechanisms of spontaneous self-location and mental body transformations during active human interaction. Using own-body imagery using spontaneous and explicit changes in self-location in standing participants, we report that spontaneous interactions with an avatar are neurally indistinguishable from explicit own-body transformation with disembodied self-location but differ from explicit own-body transformation with embodied self-location at 400-600 ms after stimulus onset. We discuss these findings with respect to the neural mechanisms of perspective-taking and self-location in spontaneous human interaction.

Spatio-temporal dynamics of olfactory processing in the human brain: an event-related source imaging study

Although brain structures involved in central nervous olfactory processing in humans have been well identified with functional neuroimaging, little is known about the temporal sequence of their activation. We recorded olfactory event-related potentials (ERP) to H(2)S stimuli presented to the left and right nostril in 12 healthy subjects. Topographic and source analysis identified four distinct processing steps between 200 and 1000 ms. Activation started ipsilateral to the stimulated nostril in the mesial and lateral temporal cortex (amygdala, parahippocampal gyrus, superior temporal gyrus, insula). Subsequently, the corresponding structures on the contralateral side became involved, followed by frontal structures at the end of the activation period. Thus, based on EEG-related data, current results suggest that olfactory information in humans is processed first ipsilaterally to the stimulated nostril and then activates the major relays in olfactory information processing in both hemispheres. Most importantly, the currently described techniques allow the investigation of the spatial processing of olfactory information at a high temporal resolution.