Temporal Dynamics of Visual Attention Measured with Event-Related Potentials

How attentional modulation on brain activities determines behavioral performance has been one of the most important issues in cognitive neuroscience. This issue has been addressed by comparing the temporal relationship between attentional modulations on neural activities and behavior. Our previous study measured the time course of attention with amplitude and phase coherence of steady-state visual evoked potential (SSVEP) and found that the modulation latency of phase coherence rather than that of amplitude was consistent with the latency of behavioral performance. In this study, as a complementary report, we compared the time course of visual attention shift measured by event-related potentials (ERPs) with that by target detection task. We developed a novel technique to compare ERPs with behavioral results and analyzed the EEG data in our previous study. Two sets of flickering stimulus at different frequencies were presented in the left and right visual hemifields, and a target or distracter pattern was presented randomly at various moments after an attention-cue presentation. The observers were asked to detect targets on the attended stimulus after the cue. We found that two ERP components, P300 and N2pc, were elicited by the target presented at the attended location. Time-course analyses revealed that attentional modulation of the P300 and N2pc amplitudes increased gradually until reaching a maximum and lasted at least 1.5 s after the cue onset, which is similar to the temporal dynamics of behavioral performance. However, attentional modulation of these ERP components started later than that of behavioral performance. Rather, the time course of attentional modulation of behavioral performance was more closely associated with that of the concurrently recorded SSVEPs analyzed. These results suggest that neural activities reflected not by either the P300 or N2pc, but by the SSVEPs, are the source of attentional modulation of behavioral performance.     

Interictal Neurocognitive Processing of Visual Stimuli in Migraine: Evidence from Event-Related Potentials

Research has established decreased sensory habituation as a defining feature in migraine, while decreased cognitive habituation has only been found with regard to cognitive assessment of the relative probability of the occurrence of a stimulus event. Our study extended the investigation of interictal habituation in migraine to include cognitive processing when viewing of a series of visually-complex images, similar to those we encounter on the internet everyday. We examined interictal neurocognitive function in migraine from a habituation perspective, using a novel paradigm designed to assess how the response to a series of images changes over time. Two groups of participants--migraineurs (N = 25) and non-migraine controls (N = 25)--were asked to view a set of 232 unfamiliar logos in the context of a target identification task as their brain electrical responses were recorded via event-related potentials (ERPs). The set of logos was viewed serially in each of 10 separate trial blocks, with data analysis focusing on how the ERP responses to the logos in frontal electrodes from 200-600 ms changed across time within each group. For the controls, we found that the amplitude of the late positive potential (LPP) ERP component elicited by the logos had no significant change across trial blocks. In contrast, in migraineurs we found that the LPP significantly increased in amplitude across trial blocks, an effect consistent with a lack of habituation to visual stimuli seen in previous research. Our findings provide empirical support abnormal cognitive processing of complex visual images across time in migraineurs that goes beyond the sensory-level habituation found in previous research.     

Event-Related Potentials Dissociate Effects of Salience and Space in Biased Competition for Visual Representation

Background

Selective visual attention is the process by which the visual system enhances behaviorally relevant stimuli and filters out others. Visual attention is thought to operate through a cortical mechanism known as biased competition. Representations of stimuli within cortical visual areas compete such that they mutually suppress each others'' neural response. Competition increases with stimulus proximity and can be biased in favor of one stimulus (over another) as a function of stimulus significance, salience, or expectancy. Though there is considerable evidence of biased competition within the human visual system, the dynamics of the process remain unknown.

Methodology/Principal Findings

Here, we used scalp-recorded electroencephalography (EEG) to examine neural correlates of biased competition in the human visual system. In two experiments, subjects performed a task requiring them to either simultaneously identify two targets (Experiment 1) or discriminate one target while ignoring a decoy (Experiment 2). Competition was manipulated by altering the spatial separation between target(s) and/or decoy. Both experimental tasks should induce competition between stimuli. However, only the task of Experiment 2 should invoke a strong bias in favor of the target (over the decoy). The amplitude of two lateralized components of the event-related potential, the N2pc and Ptc, mirrored these predictions. N2pc amplitude increased with increasing stimulus separation in Experiments 1 and 2. However, Ptc amplitude varied only in Experiment 2, becoming more positive with decreased spatial separation.

Conclusions/Significance

These results suggest that N2pc and Ptc components may index distinct processes of biased competition—N2pc reflecting visual competitive interactions and Ptc reflecting a bias in processing necessary to individuate task-relevant stimuli.     

Erratum to: Functional Brain Organization of Global and Local Visual Perception: An Event-Related Potentials Study

Adult subjects were asked to recognize a hierarchical visual stimulus (a letter) while their attention was drawn to either the global or local level of the stimulus. Event-related potentials (ERP) and behavioral indices (reaction time and percentage of correct responses) were measured. An analysis of behavioral indices showed the global level precedence effect, i.e. the increase in a small letter recognition time when this letter is a part of incongruent stimulus. An analysis of ERP components showed level-related (global vs. local) differences in the timing and topography of the brain organization of perceptual processing and regulatory mechanisms of attention. Visual recognition at the local level was accompanied by (1) stronger activation of the visual associative areas (P _z and T ₆) at the stage of sensory features analysis (P1 ERP component), (2) involvement mainly of inferior temporal cortices of the right hemisphere (T ₆) at the stage of sensory categorization (P2 ERP component), and (3) involvement of prefrontal cortex of the right hemisphere at the stage of selection of the relevant features of the target (N2 ERP component). Visual recognition at the global level was accompanied by (1) pronounced involvement of mechanisms of early sensory selection (N1 ERP component), (2) prevailing activation of parietal cortex of the right hemisphere (P ₄) at the stage of sensory categorization (P2 ERP component) as well as at the stage of the target stimulus identification (P3 ERP component). We suggested that perception of the hierarchical stimulus at the global level is related primarily to the analysis of its spatial features in the dorsal visual system whereas the perception at the local level primarily involves an analysis of the object-related features in the ventral visual system.     

The Effect of the Physical Presence of Co-Players on Perceived Ostracism and Event-Related Brain Potentials in the Cyberball Paradigm

The affective and cognitive mechanisms elicited by the experience of social exclusion—or ostracism—have recently been explored using behavioral and neurocognitive methods. Most of the studies took advantage of the Cyberball paradigm, a virtual ball tossing game with presumed co-players connected via the internet. Consistent behavioral findings indicate that exclusion obviously threatens fundamental social needs (belonging, self-esteem, meaningful existence, and control) and lowers mood. In this study, we followed the question whether the credibility of the setting affects the processing of social exclusion. In contrast to a control group (standard Cyberball setup), co-players were physically present in an experimental group. Although the credibility of the virtual ball tossing game was significantly enhanced in the experimental group, self-reported negative mood and need threat were not enhanced compared to the control group. Event-related brain potentials (ERPs), however, indicated a differential processing of social exclusion. The N2 amplitude triggered by occasional ball receptions was significantly reduced in the experimental group. This effect was restricted for an early time range (130–210 ms), and did not extend to the following P3 components. The ERP effect in the N2 time range can be related to a differential social reward processing in ostracism if co-players are physically present. The lack of a corresponding correlate in the behavioral data indicates that some facets of ostracism processing are not covered by questionnaire data.     

Locus of Psychological Control and Peculiarities of Event-Related EEG Potentials

In a group including 74 adults of both sexes, we examined interrelations between the locus of psychological control (diagnosed using the Rotter questionnaire) and parameters of event-related EEG potentials, ERPs, recorded in the course of performance of two behavioral test acts with a motor component. Task A corresponded to maximally fast pushing on the button after a signal with warning; the time of the sensorimotor reaction was measured. Task B included internal counting of a definite time interval limited by two pushings on the button. Under these conditions, we recorded the contingent negative variation (CNV), the P300 potential, and, in task B, the readiness potential (RP). EEG leads C3 and C4, according to the 10-20 system, were used. Internals (estimates by the questionnaire, 6 stens or higher) were characterized by higher amplitudes of the terminal CNV (CNV-T), integral CNV, and P300 in task A, by greater RP and CNV amplitudes in task B, and also by shorter reaction times and their smaller dispersion. It should be supposed that the corresponding peculiarities of the neurodynamic constitution of an individual are determined, to a considerable extent, by the specificity of organization and functioning of a few neurotransmitter (aminergic in particular) and neurohumoral systems.     

Psychological Adaptation Potential of the Personality: Peculiarities of Event-Related EEG Potentials

In a group of 68 adults of both sexes, we examined correlations between the level of psychological adaptability of the personality (diagnosed using the Maklakov questionnaire) and parameters of event-related potentials (ERPs) recorded in the course of performance of two behavioral test acts including a motor component. In task A, it was necessary to maximally rapidly press the button after an imperative signal preceded by a warning signal, while a definite time interval (limited by two pressings of the button) should be measured in task B. Parameters of the contingent negative variation, CNV, potential P300 and, in task B, readiness potential, RP, were measured in C3 and C4 leads. High amplitudes of ERPs (RP, P300, and CNV in task A) and smaller variability of the indices of working efficiency corresponded, in the whole, to higher estimates of psychological adaptability in general and of separate aspects of the latter estimated according to the scales of the used questionnaire. Probable mechanisms of the peculiarities of neurodynamic constitution determining the level of the psychological adaptability of the individual, on the one hand, and of the ERP parameters, on the other hand, are discussed.     

A Coronary-Prone Type of Personality: Peculiarities of Event-Related EEG Potentials

In a group of 70 adults of both sexes, we examined interrelations between the estimates of expression of a coronary-prone type (type A) of the personality (measured using the Jenkins questionnaire) and the parameters of event-related EEG potentials (ERPs). The latter potentials were recorded in the course of performance of two behavioral test tasks including motor components. Within the framework of the “A” task, the subject is had to maximally rapidly push the button after a signal with warning (with measurement of the latency of the sensorimotor reaction); under these conditions, we recorded the contingent negative variation (CNV) and P300 potential. In the case of the “B” task, a definite time interval was to be measured and limited by two pressings of the button. In this task, the readiness potential (RP) was recorded in addition to the CNV and P300. The C3 and C4 EEG leads (according to the 10–20 system) were used. Within the framework of the “A” task, subjects belonging to the coronary-prone type were characterized by the lowest amplitudes of the CNV and its separate components and also by greater amplitudes and relatively long latencies of the P300 wave. Persons of type B were distinguished by the highest CNV amplitudes in both hemispheres, while values of the P300 amplitude in this group were usually medium. In the “B” task, representatives of type A demonstrated the lowest RP and P300 amplitudes, especially clearly pronounced negative CNVs in the left hemisphere, and relatively long P300 latencies; individuals belonging to type B showed the highest RP and CNV amplitudes in the right hemisphere and medium values of the P300 amplitude. The correlations found are probably due, to a considerable extent, to the fact that both characteristics of the behavioral types A and B and amplitude parameters of ERPs depend significantly on genetically determined neurochemical factors, namely specificities of organization and functioning of a few neurotransmitter (in particular, aminergic) and neurohumoral systems.     

Individual Differences in the Recognition of Facial Expressions: An Event-Related Potentials Study

Previous studies have shown that early posterior components of event-related potentials (ERPs) are modulated by facial expressions. The goal of the current study was to investigate individual differences in the recognition of facial expressions by examining the relationship between ERP components and the discrimination of facial expressions. Pictures of 3 facial expressions (angry, happy, and neutral) were presented to 36 young adults during ERP recording. Participants were asked to respond with a button press as soon as they recognized the expression depicted. A multiple regression analysis, where ERP components were set as predictor variables, assessed hits and reaction times in response to the facial expressions as dependent variables. The N170 amplitudes significantly predicted for accuracy of angry and happy expressions, and the N170 latencies were predictive for accuracy of neutral expressions. The P2 amplitudes significantly predicted reaction time. The P2 latencies significantly predicted reaction times only for neutral faces. These results suggest that individual differences in the recognition of facial expressions emerge from early components in visual processing.     

Distributed Patterns of Event-Related Potentials Predict Subsequent Ratings of Abstract Stimulus Attributes

Exposure to pleasant and rewarding visual stimuli can bias people''s choices towards either immediate or delayed gratification. We hypothesised that this phenomenon might be based on carry-over effects from a fast, unconscious assessment of the abstract ‘time reference’ of a stimuli, i.e. how the stimulus relates to one''s personal understanding and connotation of time. Here we investigated whether participants'' post-experiment ratings of task-irrelevant, positive background visual stimuli for the dimensions ‘arousal’ (used as a control condition) and ‘time reference’ were related to differences in single-channel event-related potentials (ERPs) and whether they could be predicted from spatio-temporal patterns of ERPs. Participants performed a demanding foreground choice-reaction task while on each trial one task-irrelevant image (depicting objects, people and scenes) was presented in the background. Conventional ERP analyses as well as multivariate support vector regression (SVR) analyses were conducted to predict participants'' subsequent ratings. We found that only SVR allowed both ‘arousal’ and ‘time reference’ ratings to be predicted during the first 200 ms post-stimulus. This demonstrates an early, automatic semantic stimulus analysis, which might be related to the high relevance of ‘time reference’ to everyday decision-making and preference formation.     

Distinct Features of Auditory Steady-State Responses as Compared to Transient Event-Related Potentials

Transient event-related potentials (ERPs) and steady-state responses (SSRs) have been popularly employed to investigate the function of the human brain, but their relationship still remains a matter of debate. Some researchers believed that SSRs could be explained by the linear summation of successive transient ERPs (superposition hypothesis), while others believed that SSRs were the result of the entrainment of a neural rhythm driven by the periodic repetition of a sensory stimulus (oscillatory entrainment hypothesis). In the present study, taking auditory modality as an example, we aimed to clarify the distinct features of SSRs, evoked by the 40-Hz and 60-Hz periodic auditory stimulation, as compared to transient ERPs, evoked by a single click. We observed that (1) SSRs were mainly generated by phase synchronization, while late latency responses (LLRs) in transient ERPs were mainly generated by power enhancement; (2) scalp topographies of LLRs in transient ERPs were markedly different from those of SSRs; (3) the powers of both 40-Hz and 60-Hz SSRs were significantly correlated, while they were not significantly correlated with the N1 power in transient ERPs; (4) whereas SSRs were dominantly modulated by stimulus intensity, middle latency responses (MLRs) were not significantly modulated by both stimulus intensity and subjective loudness judgment, and LLRs were significantly modulated by subjective loudness judgment even within the same stimulus intensity. All these findings indicated that high-frequency SSRs were different from both MLRs and LLRs in transient ERPs, thus supporting the possibility of oscillatory entrainment hypothesis to the generation of SSRs. Therefore, SSRs could be used to explore distinct neural responses as compared to transient ERPs, and help us reveal novel and reliable neural mechanisms of the human brain.     

Investigating the Effects of Antipsychotics and Schizotypy on the N400 Using Event-Related Potentials and Semantic Categorization

Within the field of cognitive neuroscience, functional magnetic resonance imaging (fMRI) is a popular method of visualizing brain function. This is in part because of its excellent spatial resolution, which allows researchers to identify brain areas associated with specific cognitive processes. However, in the quest to localize brain functions, it is relevant to note that many cognitive, sensory, and motor processes have temporal distinctions that are imperative to capture, an aspect that is left unfulfilled by fMRI’s suboptimal temporal resolution. To better understand cognitive processes, it is thus advantageous to utilize event-related potential (ERP) recording as a method of gathering information about the brain. Some of its advantages include its fantastic temporal resolution, which gives researchers the ability to follow the activity of the brain down to the millisecond. It also directly indexes both excitatory and inhibitory post-synaptic potentials by which most brain computations are performed. This sits in contrast to fMRI, which captures an index of metabolic activity. Further, the non-invasive ERP method does not require a contrast condition: raw ERPs can be examined for just one experimental condition, a distinction from fMRI where control conditions must be subtracted from the experimental condition, leading to uncertainty in associating observations with experimental or contrast conditions. While it is limited by its poor spatial and subcortical activity resolution, ERP recordings’ utility, relative cost-effectiveness, and associated advantages offer strong rationale for its use in cognitive neuroscience to track rapid temporal changes in neural activity. In an effort to foster increase in its use as a research imaging method, and to ensure proper and accurate data collection, the present article will outline – in the framework of a paradigm using semantic categorization to examine the effects of antipsychotics and schizotypy on the N400 – the procedure and key aspects associated with ERP data acquisition.     

Humor as a Reward Mechanism: Event-Related Potentials in the Healthy and Diseased Brain

Humor processing involves distinct processing stages including incongruity detection, emotional response, and engagement of mesolimbic reward regions. Dysfunctional reward processing and clinical symptoms in response to humor have been previously described in both hypocretin deficient narcolepsy-cataplexy (NC) and in idiopathic Parkinson disease (PD). For NC patients, humor is the strongest trigger for cataplexy, a transient loss of muscle tone, whereas dopamine-deficient PD-patients show blunted emotional responses to humor. To better understand the role of reward system and the various contributions of hypocretinergic and dopaminergic mechanisms to different stages of humor processing we examined the electrophysiological response to humorous and neutral pictures when given as reward feedback in PD, NC and healthy controls. Humor compared to neutral feedback demonstrated modulation of early ERP amplitudes likely corresponding to visual processing stages, with no group differences. At 270 ms post-feedback, conditions showed topographical and amplitudinal differences for frontal and left posterior electrodes, in that humor feedback was absent in PD patients but increased in NC patients. We suggest that this effect relates to a relatively early affective response, reminiscent of increased amygdala response reported in NC patients. Later ERP differences, corresponding to the late positive potential, revealed a lack of sustained activation in PD, likely due to altered dopamine regulation in reward structures in these patients. This research provides new insights into the temporal dynamics and underlying mechanisms of humor detection and appreciation in health and disease.     

Correlations of the Peculiarities of the Motivational Sphere and Characteristics of Event-Related EEG Potentials in Humans

We studied the relations between generalized characteristics of the state of the motivational sphere, the levels of need for achievements (N-Ach) and achievement motivation (AchM) typical of an individual, and the parameters of cerebral event-related potentials (ERPs). The examined group included 70 adults of both sexes. The ERPs were recorded in the course of realization of two behavioral test acts with motor components. In task А, the subject should press a button with the minimum delay with respect to an imperative signal preceded by a warning signal (with the measurement of the time of sensorimotor reaction); in this case, the contingent negative variation (CNV) and Р300 potential were recorded. Under conditions of task B, the subject should measure a definite time interval limiting the latter by two pushings of the button; in this case, the readiness potential (RP) was recorded in addition to CNV and Р300. The ERPs were recorded in the С3 and С4 leads (according to the 10-20 system). The peculiarities of the motivational sphere were diagnosed using Orlov’s and Mechrabian’s questionnaires. We found that a relatively high amplitude of the early CNV component (СNV-O) and low amplitudes of the integral CNV and Р300 in task A and a low amplitude of the RP can serve as task B-related EEG markers of a high NA level. In task A, high levels of the AchM correlated with higher amplitudes of the CNV and Р300, and amplitudes of these potentials were higher in the left hemisphere. The observed interrelations were probably determined by a considerable dependence of the N-Ach and AchM characteristics, on the one hand, and CNV amplitude parameters, on the other hand, on the hereditary factors, in particular neurochemical ones. It is obvious that such peculiarities of the neurodynamic constitution of an individual are, to a considerable extent, determined by the specificity of organization and functioning of a few neurotransmitter (in particular aminergic) and neurohumoral systems.     

Distinct Modulation of Event-Related Potentials during Motor Preparation in Patients with Motor Conversion Disorder

Objective

Conversion paresis patients and healthy people feigning weakness both exhibit weak voluntary movement without detectable neuropathology. Uniquely, conversion patients lack a sense of conscious awareness of the origin of their impairment. We investigated whether conversion paresis patients show distinct electroencephalographic (EEG) markers associated with their unconscious movement deficits.

Methods

Six unilateral upper limb conversion paresis patients, 12 feigning participants asked to mimic weakness and 12 control participants performed a precued reaction time task, requiring movements of either hand, depending on precue information. Performance measures (force, reaction and movement time), and event-related EEG potentials (ERP) were compared, between groups and across hands or hemisphere, using linear mixed models.

Results

Feigners generated the same inter-hand difference in reaction and movement time as expressed by patients, even though no specific targets were set nor feedback given on these measures. We found novel ERP signatures specific to patients. When the symptomatic hand was precued, the P3 ERP component accompanying the precue was dramatically larger in patients than in feigning participants. Additionally, in patients the earlier N1 ERP component was diminished when the precue signalled either the symptomatic or asymptomatic hand.

Conclusions

These results are consistent with previous suggestions that lack of awareness of the origin of their symptoms in conversion disorder patients may result from suppression of brain activity normally related to self-agency. In patients the diminished N1 to all precues is consistent with a generalised reduction in cognitive processing of movement-related precues. The P3 enhancement in patients is unlikely to simply reflect changes required for generation of impaired movements, because it was not seen in feigners showing the same behavioural deficits. Rather, this P3 enhancement in patients may represent a neural biomarker of unconscious processes, including additional emotional loading, related to active suppression of brain circuits involved in the attribution of self-agency.     

Identification of Event-Related Potentials Elicited by Conceptual Mismatch Between Expectations and Self-chosen TV Images

When a voluntary action is followed by an unexpected stimulus, a late positive potential (LPP) with a posterior scalp distribution is elicited in a latency range of 500–700 ms. In the present study, we examined what type of mismatch between expectations and action outcomes was reflected by the LPP. Twelve student volunteers participated in a task simulating choice of TV programs. After choosing one of three options displayed as a cue stimulus, they viewed a second stimulus (still TV image). To manipulate the type of expectation, three kinds of cue conditions were used: thumbnail image condition (three small TV images), category label condition (three words), and no cue condition (three question marks). Over trials, the second stimulus either matched (p = .80) or mismatched (p = .20) the chosen option. As compared to matched TV images, mismatched TV images elicited a larger LPP (500–700 ms) in the thumbnail image and category label conditions. In addition, a larger centroparietal P3 (400–450 ms) was elicited to mismatched TV images in the thumbnail image condition alone. LPP reflects a conceptual mismatch between a category-based expectation and an ensuing action outcome, whereas P3 reflects a perceptual mismatch between an image-based expectation and an action outcome.     

Inhibition in Adults with Attention Deficit/Hyperactivity Disorder: Event-Related Potentials in the Stop Task

The core deficit in Attention Deficit/Hyperactivity Disorder (ADHD) may be a deficiency in executive functions, particularly the processes that are associated with the inhibition of predominant responses. To test this notion in the adult population, healthy undergraduate volunteers and students with ADHD symptoms performed a visual Stop Signal Task (Logan et al. J Exp Psychol: Hum Percept Perform 10:276–291, 1984) while Event-Related brain Potentials were recorded. The two groups did not differ on behavioral measures of performance, but there was a significant difference in the N2–P3 component. These results underline the robustness of an N2–P3 difference between healthy adults and people with ADHD symptoms that have persisted into young adulthood.     

Dependence of the Parameters of Visual Evoked Potentials on the Parameters of a Complex Visual Stimulus (Tests on Humans)

We recorded visual evoked potentials, VEP, elicited by presentation of a reversal chess pattern; 35 healthy persons were examined. A recording electrode was in point Oz, according to the 10-20 system; dimensions of the chess pattern square fields and their contrast varied from 1.8 to 120 and from 2 to 100%, respectively. Peak latencies, PL, of the N75 component depended on the contrast of stimulus elements in a U-like manner with the minimum within a 20-25% range. The PL of the P100 component monotonically increased with a decrease in the contrast, while the dependence of the PL of N145 was complex: a trend toward a decrease with a decrease in contrast to 30%, a local maximum in about 25%, a decrease and stabilization within a 15-4% range, and a sharp increase at the minimum contrast. The amplitude of N75 decreased with decrease in contrast down to 20-25% and then stabilized; the amplitude of P100 decreased in an S-like mode, with a plateau within 25-4%. The dependence of the N145 amplitude was complex, with a plateau-like maximum at 30-15% contrast. The amplitudes of the negative VEP components, N75 and N145, increased with an increase in the square dimensions to 7.5 and then decreased. Changes in the P100 amplitude included two phases, with a local minimum within an angular dimension range of 30-15^O. The PL of all analyzed components in general increased with a decrease in the angular dimension of the pattern components. The above data are discussed considering concepts on the genesis of different VEP components and on the existence of specialized channels in the visual system, which are responsible for detection of different parameters of a visual object. The complex dynamics of the PL of the analyzed VEP components and of the P100 amplitude related to variation of the contrast and angular dimensions of the elements of a complex stimulus are considered to be determined by a module principle of the organization of the elements constituting different levels of the visual system and by transformations of the receptive fields of these elements on the level of cortical modules, which are related to changes in the stimulus parameters.