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.     

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.     

Correlations between the level of aggressiveness of personality and characteristics of event-related EEG potentials

In a group of 76 adults of both sexes, we examined interrelations between the level of aggressiveness of the individual (diagnosed using the Buss-Durkee Hostility Inventory) and parameters of event-related EEG potentials (ERPs) recorded under conditions of two behavioral test acts including a motor component. Within the framework of task A, the subject must push a button with the shortest delay after an executory signal preceded by a warning signal; the time of sensorimotor reaction was measured. Under these conditions, we recorded the contingent negative variayion (CNV) and the P300 potential. In the case of task B, it was necessary to measure a definite time interval limited by two pushings of the button. Under these conditions, the readiness potential (RP) was recorded in addition to the CNV and P300. The C3 and C4 leads were used (according to the 10–20 system); the time constant of an amplification tract was 10 sec. Despite natural broad interindividual variability, high amplitudes of the recorded ERPs (RP, CNV, and P300) in general corresponded to lower indices by scales of the Buss-Durkee inventory and smaller values of the indices of aggressiveness and hostility. These interrelations are, probably, based on the fact that both characteristics of aggressiveness of the personality and EEG amplitude parameters are to a considerable extent determined by hereditary factors. It is believed that the respective peculiarities of the neurodynamic constitution of the individual are to a great extent dependent on the specificities of organization and functioning of a few neurotransmitter (in particular, aminergic) and neurohumoral systems. Neirofiziologiya/Neurophysiology, Vol. 39, No. 2, pp. 154–164, March–April, 2007.     

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.     

Individual personality-related characteristics of event-related EEG potentials recorded in an experimental situation requiring production of time intervals

Event-related EEG potentials (ERP) were recorded from 75 tested adult men and women; recording was performed from C3 and C4 points. The experimental situation required internal counting of time intervals limited by two pushes of a button. The experimental paradigm provided a substantial level of uncertainty, and a high level of attention needed to be maintained. The tested subjects were not informed by the experimenter about the precise value of the preset time interval; they knew only its limits, 17–23 sec. The subject obtained information about the agreement or disagreement between the produced interval and its value preset by the experimenter by visual feedback signals obtained 2 sec after termination of counting; in the case of agreement the subject had to perform a confirming (third) push of the button. Pushes were preceded by readiness potentials (RP); contingent negative variation (CNV) developed before the feedback signals, and the latter were accompanied by P300 potentials. Significant positive correlations were found between the parameters of RP and P300 in both hemispheres. In general, ERP were characterized by very high interindividual variability, which in a few respects correlated with the personality-related characteristics of tested subjects evaluated by psychological testing with the use of corresponding questionnaires. In particular, under the experimental conditions used, negative correlations were observed between the RP amplitude and psychotism indices, CNV amplitude and emotional stability; CNV amplitude and extroversive features, and P300 amplitude and domination properties of a person. Positive correlations were observed between the CNV amplitude and autia factor (according to Eysenck’s PEN and Cattell’s 16 PF questionnaires). We suppose that correlations between the personal psychical features and ERP parameters are grounded in both inherited constitutional specificities of the nervous system and neurochemical/structural modifications in the brain determined by the acquired vital experience.     

Readiness to respond in a target detection task: pre- and post-stimulus event-related potentials in normal subjects

Brain potentials were recorded from 12 normal subjects engaged in an auditory target detection task (target stimulus probability of 0.2, stimulus rate of 1 every 2 sec) when instructions were (1) to press a response button with the thumb of the dominant hand to each target or (2) to keep a mental count of each target. A pre-stimulus slow negative potential was identified before every stimulus except non-targets immediately after targets. The amplitude of the pre-stimulus negativity was significantly affected by task instructions and was up to 4 times larger during the button press than the mental count condition. In contrast, the amplitudes and latencies of the event-related components (N100, P200, N200 and P300), when slow potentials were removed by filtering, were not different as a function of press or count instructions. The immediately preceding stimulus sequence affected both the amplitude and onset latency of the pre-stimulus negativity; both measures increased as the number of preceding non-targets increased. The amplitude of the pre-stimulus negative shift to targets also increased significantly as RT speed decreased. The major portion of the pre-stimulus negative potential is considered a readiness potential (RP) reflecting preparations to make a motor response. The amplitude of the RP during the target detection task did not significantly lateralize in contrast to the RP accompanying self-paced movements.     

The recovery functions of auditory event-related potentials during split-second discriminations

We examined the recovery cycles of auditory event-related potentials (ERPs) in a high-speed auditory discrimination task and in passive conditions. Each trial contained 3 tones cued by a warning flash. In passive conditions, auditory ERPs consisted mainly of N1 (108 msec) and P2 (213 msec) components superimposed on a small CNV. The N1 and P2 were comparable in amplitude and both had prolonged refractory periods. In discriminative reaction time (DRT) conditions the same tones cued or inhibited press responses and elicited additional endogenous components (principally the Nd and P3). ERPs in DRT conditions were superimposed upon a prominent CNV that began after the warning cue and lasted throughout the signal delivery period.The N1 was larger in active than passive conditions and showed less marked refractory effects, while the P2 was smaller and showed more marked refractoriness. Differences between active and passive conditions could be explained by the presence of an endogenous negative potential (the Nd) with a short refractory period that was superimposed upon the N1 and P2.The P3 was recorded only in active conditions. At short ISIs (0.5 sec), P3 amplitudes were reduced and P3 latencies lengthened in parallel with prolongations in reaction time due to so-called psychological refractory period (PRP) effects. Both P3 recovery and the PRP reflected central mechanisms since they were observed at short ISIs when stimuli cueing different responses succeeded one another.N1 and P3 amplitudes diminished over the course of the experiment in both active and passive conditions. The decrease (amounting to about 30% of initial amplitudes) did not appear due to reductions in vigilance, since it was not accompanied by changes in reaction time or response accuracy, or by changes in other endogenous components (CNV or Nd). Short-term N1 habituation was unaffected by long-term amplitude reductions suggesting that independent mechanisms were responsible for the two phenomena.     

ERP Correlates of Proactive and Reactive Cognitive Control in Treatment-Na?ve Adult ADHD

This study investigated whether treatment naïve adults with Attention Deficit Hyperactivity Disorder (ADHD; n = 33; 19 female) differed from healthy controls (n = 31; 17 female) in behavioral performance, event-related potential (ERP) indices of preparatory attention (CueP3 and late CNV), and reactive response control (Go P3, NoGo N2, and NoGo P3) derived from a visual cued Go/NoGo task. On several critical measures, Cue P3, late CNV, and NoGo N2, there were no significant differences between the groups. This indicated normal preparatory processes and conflict monitoring in ADHD patients. However, the patients had attenuated Go P3 and NoGoP3 amplitudes relative to controls, suggesting reduced allocation of attentional resources to processes involved in response control. The patients also had a higher rate of Go signal omission errors, but no other performance decrements compared with controls. Reduced Go P3 and NoGo P3 amplitudes were associated with poorer task performance, particularly in the ADHD group. Notably, the ERPs were not associated with self-reported mood or anxiety. The results provide electrophysiological evidence for reduced effortful engagement of attentional resources to both Go and NoGo signals when reactive response control is needed. The absence of group differences in ERP components indexing proactive control points to impairments in specific aspects of cognitive processes in an untreated adult ADHD cohort. The associations between ERPs and task performance provided additional support for the altered electrophysiological responses.     

Who Are the True Fans? Evidence from an Event-Related Potential Study

Fans of celebrities commonly exist in modern society. Researchers from social science have been concerned with this problem for years. Furthermore, such researchers have attempted to measure people’s involvement with celebrities in various ways. However, no study measured the degree of addiction to a specific celebrity at the neurological level. Therefore, the current study employed visually evoked event related potentials (ERPs) to examine people’s attitude toward celebrities by comparing different brain activities of fans and non-fans when they were shown a set of photos. These photos include a specific celebrity, a familiar person, a stranger and a butterfly. Furthermore, to examine the validity of the detected neural index, we also investigated the correlation between brain activity and the score of the Celebrity Attitude Scale (CAS), which was a questionnaire used to explore people’s attitude toward celebrities at behavioral level. Two groups of subjects were asked to complete an implicit task, i.e., to press a button when a picture of a butterfly appeared. Results revealed that fans showed significant positive N2 and P300 deflection when viewing the photos of their favorite celebrity, whereas in the non-fan group, the subjects only showed larger P300 amplitude as a response to the celebrity’s photos. Furthermore, a positive correlation between P300 amplitude elicited by the stimuli of a celebrity face and CAS scores was also observed. These findings indicated fan attitude to a specific celebrity can also be observed at the neurological level and suggested the potential utility of using ERP component as an index of fandom involvement.     

Slow potentials of the prefrontal cortex in dogs and the classical secretory conditioned reflex

Slow potentials (CNV and component P300) were recorded in the medial part of the prefrontal cortex of dogs trained to classical secretory conditioned reflex and its differentiation. CNV increased when the conditioned stimulus was preceded by a signal of different meaning, as compared with CNV to the same conditioned signal following the stimulus of the same meaning; the greatest values of CNV and P300 were observed in response to differential stimulus preceded by a positive signal.     

Time-locked and phase-locked features of P300 event-related potentials (ERPs) for brain–computer interface speller

The brain–computer interface P300 speller is aimed to help those patients unable to activate muscles to spell words by utilizing their brain activity. However, a problem associated with the use of this brain–computer interface paradigm is the generation mechanics of P300 related to responses to visual stimuli. Herein, we investigated the event-related potential (ERP) response for the P300-based brain–computer interface speller. A signal preprocessing method integrated coherent average, principal component analysis (PCA) and independent component analysis (ICA) to reduce the dimensions and noise in the raw data. The time–frequency analysis was based on wavelet and two characteristic parameters of event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) were computed to indicate the evoked response (time-locked) and phase reset (phase-locked) activity, respectively. Results demonstrated that the proposed method was valid for the time-locked and phase-locked feature extraction and both the evoked response and phase reset contributed to the genesis of the P300 signal. These electrophysiological responses characteristics of ERPs would be used for BCI P300 speller design and its signal processing strategies.     

P300 from a passive auditory paradigm

The P300 (P3) event-related brain potential (ERP) was elicited with a passive tone sequence paradigm and evaluated in 2 studies. Experiment 1 compared ERPs from the passive procedure with those from an active discrimination (oddball) task. The passive sequence paradigm yielded P3 wave forms remarkably similar to those obtained from the active task since both demonstrated central-parietal maximum scalp distributions and virtually identical peak latencies. No differences between tasks were found when ERPs were elicited with subject's eyes open or closed. Experiment 2 compared ERPs from the passive sequence paradigm obtained when subjects were attempting to solve a word puzzle with those from a simple ignore condition. The puzzle-solving secondary task produced a decrease in P3 amplitude relative to the ignore condition, although P3 peak latency was unaffected. These results suggest that the passive sequence paradigm may be a useful and reliable means of eliciting the P3 ERP in subject populations or experimental situations in which an active discrimination task cannot be performed.     

Adaptation to the complexity of a task (a P300 study)

In numerous studies the P300 component of the event-related brain potential (ERP) has been shown to occur in connection with stimulus evaluation processes. 10 healthy right-handed volunteers (3 women, 7 men) aged from 25 to 30 years (mean age 27.8 years) participated in the experiments. One of 5 equiprobably occurring two-letter strings appeared on the screen always at the same central location. The strings informed the subjects about the difficulty of subsequently presented mental arithmetic tasks. After the letter strings vanished from the screen the subjects were to press the space-bar whereby a mental arithmetic task was presented corresponding in difficulty to the preceding message. The EEG was recorded by means of Ag/AgCl electrodes from frontal (F zeta), central (C zeta) and parietal (P zeta) midline electrodes referenced to linked earlobes. EEG and EOG were sampled 1200 ms, starting 200 ms prior to string onset. P300 peak latencies, peak amplitudes and areas in the time range 300 to 900 ms were measured in ERPs averaged selectively for the 5 strings. The main finding was that the P300 amplitude in ERPs to the 5 different strings varied in a U-shaped trend as a function of announced task difficulty. This result gives further evidence that the P300 amplitude reflects distance between incoming information and current adaptation level at the inferred internal dimension, i.e. task difficulty in this experiment.     

Mapping P300 waves onto inhibition: Go/NoGo discrimination

Subjects viewed letters presented at 2 sec intervals and prepared a fast button press whenever an “O” appeared. If the next letter was an “X” the button press was executed (Go signal), but if the letter was a non-X character (T, H, Z) suppression of the response was required (NoGo cue). NoGo signals elicited a P300-like wave that was larger at central and frontal scalp sites contralateral to the prepared movement, compared to P300s elicited by Go cues which were symmetric about the sagittal midline and dominant at parietal sites. Subtraction of preparatory CNVs from the NoGo P300 did not remove differences in scalp topography, or reduce the amplitude of the NoGo P300 to that seen following control letters that required perceptual identification but did not call for suppression of prepared motor responses. Principal components analysis identified a middle positive wave following X-alone control stimuli whose topography resembled the NoGo P300. These findings suggest that the source of augmented NoGo P300s is a generator involved with sensorimotor inhibition. We discuss the mechanism of P300 waves and evidence linking these waves with inhibition in other task arrangements.     

A topographical ERP study of healthy premature 5 year old children in the auditory and visual modalities

The aim of this research is to study the impact of extreme prematurity on the cognitive development of the child as assessed at age 5 years 9 months. Our samples include 15 healthy prematures born between 25 and 28 weeks of gestational age carefully matched with 15 full-term controls. In the first experiment, two different auditory stimuli were presented to the subjects who listened passively without instruction. The second experiment consisted of a standard visual oddball task in which the subjects were instructed to `catch' two different animals, by pushing a left or right button for a moose (n=120) or a raccoon (n=40), respectively. In the auditory task, 3 ERP peaks were analyzed (frontal N100 and P3a, temporal P2). All premature children demonstrated normal early frontal N100 and temporal P2 responses. The group differences were apparent in the late positivity (P3a) where controls showed a larger amplitude to the rare tones applied evenly to both ears. In contrast, the prematures did not show sensitivity to rare tones but showed a larger P3a upon left ear stimulation, when compared to the right. Also, the ERPs to the visual oddball task showed normal early positivities (P250–300) in the premature group. Once again, deviations from the normal were evident in late waves. The ERPs recorded from prematures showed a more diffuse topography especially between 500 and 600 ms post-stimulus and around the posterior area (P550). The succeeding negativity (SW) was not altered in the premature group. The ERP data suggest that premature children, even without clinically apparent problems, convey specific ERP singularity when engaged in a task that involves complex processing.     

Characteristics of the parietal cortex activation in humans during different attention tasks

The cortical activation was estimated by the event-related potential (ERPs) methods during selection tasks of lateralized visual stimuli requiring different forms of attention: 1) form of stimuli, 2) stimuli position, 3) combined attention of form and position. The ERPs were recorded in 15 young healthy adults in 6 leads P3, P4, T3, T4, T5, T6, and endogenous ERPs components: CNV (contingent negative variation), N1, P3 and the complex [N1-P3]. Differences between the ERPs at "attended" and "non-attended" stimuli were considered as indices of selection attention of particular feature of visual stimuli. Such indices of form and position were revealed selectivity in parietal leads. The most eminent ERPs components, the pronounced activation gradient during increase of attention demands were revealed in parietal regions (vs. temporal ones). In our opinion, parietal cortex has a high priority in selection attention system.     

Effects of attention and slow potential shifts on self-regulation of event-related potentials

Research on the effects of self-regulation of slow potentials (SP) and event-related potentials (ERP) has failed to look at the possible interactions of these two kinds of brain potentials. The present study investigated such interactions by recording both ERP and SP potential changes in an operant ERP conditioning paradigm. Ten subjects participated in two conditions that were designed to differentially manipulate attention to the stimuli. In the operant conditioning task, subjects received auditory feedback as they attempted to increase the ERP amplitude at 180 msec poststimulus (P180), which was elicited by a subpainful shock stimulus to the forearm over 250 trials. In the distraction task, subjects were instructed not to attend to stimuli or feedback tones, but rather received and were tested on reading materials. Attention, as manipulated by these tasks, was not a determinant of changes in ERP amplitude since there were no significant differences in the size of P180 between attention conditions. While no significant change in the mean ERP amplitude occurred, subjects were able to produce ERPs above criterion threshold significantly more often during trials in the conditioning task than in the reading task. Thus, there was evidence of some learning. The difference in wave forms between hit and miss trials indicates a latency shift (with misses having a later ERP peak). This may indicate that latency, rather than, or in addition to, amplitude, is shaped during conditioning procedures. In addition, the CNV that developed between the shock stimulus and the feedback signal during conditioning was significantly larger in amplitude than in the distraction condition. This is taken as evidence of increased attention during conditioning. Since hit trials demonstrated larger contingent negative variation (CNV) amplitudes, production of CNVs may be instrumental in mediating hits. Therefore, attentional mechanisms may play a role in successful ERP self-regulation. No correlations were found involving P180, CNVs, or tonic slow potential shifts. Changes in tonic DC levels showed a suggestive trend between conditions. Although both conditions began with a negative shift, during conditioning the negativity increased, while during distraction the tonic level went to positivity. These trends support the hypothesis that attention and arousal increased during conditioning. The possible reasons for the lack of significant correlations between ERP and tonic or phasic slow potential changes in this paradigm are discussed.     

The P300 event-related potentials in dementia of the Alzheimer type. Correlations between P300 and monoamine metabolites

We studied auditory event-related potentials (ERPs) in 40 patients with dementia of the Alzheimer type (DAT). Peak latencies and amplitudes of N100, P200 and P300 components were measured. To study the possible relationships between the ERPs and monoaminergic neurotransmitter functions, CSF neurotransmitter metabolites were also analyzed. In patients with DAT, the P300 amplitude was significantly reduced and the P300 latency was prolonged. CSF concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were decreased. The P300 amplitude was significantly correlated with the 5-HIAA concentration. There were no correlations between the P300 components and the HVA concentration. These findings suggest that the serotonergic system modulates the P300 component of ERPs in patients with DAT.     

Evoked cortical activity to sounds of differing signal meaning in young and elderly subjects

In elderly people, in comparison with the young ones, the latency of wave P300 is increased in response to all applied acoustic signals, the amplitude of P300 is lower only in response to significant stimuli. No age changes of the wave N150 parameters are noticed. P300 (or N150) wave amplitude depends on signal significance of the sound; it is the lowest in response to significant stimuli and the highest to the ignored ones. Possible reasons of this paradoxical phenomenon are discussed. Preferential participation of different stages of cortical information processing is determined by the difficulty of perceptive task solution. Cortical electrical reaction to separate stimuli is significantly determined by the context of the information perceived in the given period, creating psychological state of the personality.     

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.