Task difficulty,probability, and inter-stimulus interval as determinants of P300 from auditory stimuli

The P300 event-related potential was elicited with auditory stimuli in 4 experiments which manipulated combinations of stimulus target probability (10% vs. 30%), task difficulty (easy vs. hard), and inter-stimulus interval (5 sec vs. 2 sec). P300 amplitude was smaller and peak latency longer for the more difficult relative to the easier tasks across experiments. Increases in stimulus target probability generally diminished P300 amplitude and shortened peak latency more for the easy relative to difficult task conditions. Increasing the number of non-target stimulus tones decreased P300 amplitude reliably, but increased latency only slightly. Task difficulty did not interact with variations in inter-stimulus interval which produced generally weak effects for both amplitude and latency. These findings suggests that P300 amplitude and latency obtained from auditory discrimination paradigms reflect processing difficulty independently of stimulus target probability unless differences in task requirements affect stimulus encoding.     

Pain-related and cognitive components of somatosensory evoked potentials following CO2 laser stimulation in man

We recorded cortical potentials evoked by painful CO₂ laser stimulation (pain SEP), employing an oddball paradigm in an effort to demonstrate event-related potentials (ERP) associated with pain. In 12 healthy subjects, frequent (standard) pain stimuli (probability 0.8) were delivered to one side of the dorsum of the left hand while rare (target) pain stimuli (probability 0.2) were delivered to the other side of the same hand. Subjects were instructed to perform either a mental count or button press in response to the target stimuli. Two early components (N2 and P2) of the pain SEP demonstrated a Cz maximal distribution, and showed no difference in latency, amplitude or scalp topography between the oddball conditions or between response tasks. In addition, another positive component (P3) following the P2 was recorded maximally at Pz only in response to the target stimuli with a peak latency of 593 msec for the count task and 560 msec for the button press task. Its scalp topography was the same as that for electric and auditory P3. The longer latency of pain P3 can be explained not only by its slower impulse conduction but also by the effects of task difficulty in the oddball paradigm employing the pain stimulus compared with electric and auditory stimulus paradigms. It is concluded that the P3 for the pain modality is mainly related to a cognitive process and corresponds to the P3 of electric and auditory evoked responses, whereas both N2 and P2 are mainly pain-related components.     

P300 from a single auditory stimulus

The P3(00) event-related brain potential (ERP) was elicited with auditory stimuli to compare 2 different discrimination tasks. The oddball paradigm presented both target and standard tones; the single-stimulus paradigm presented at target but no standard tone stimulus. Experiment 1 manipulated target stimulus probability (0.20, 0.50, 0.80) and produced highly similar P3 amplitude and latency results across probability levels for each paradigm. Experiment 2 factorially varied inter-stimulus interval (2 sec, 6 sec) and target stimulus probability (0.20, 0.80). P3 amplitude and latency were highly similar for both the oddball and single-stimulus procedures across all conditions.     

P300 in response to the subject's own name

The P300 component is influenced by task relevance which is typically achieved by employing an active task involving the evoking stimulus. This study explored the possibility of making use of the subject's name, which is innately relevant to the subject, to achieve stimulus relevance.Dependence of P300 amplitude on auditory presentation of the subject's name was assessed in two experiments in which no response was required: (1) a passive 2-word “oddball” paradigm where the low probability word was the subject's first name; (2) a passive 3-word “oddball” paradigm consisting of two low probability words, one of which was the subject's name, and a third, high probability word.In the first experiment, a typical active 2-word “oddball” paradigm, which did not include the subject's name, was compared with the passive paradigm.P300 amplitude was larger in response to the subject's name compared to the other word in the two-word paradigm, indicating that the name can be used to evoke P300 in a passive paradigm. It was also larger than either of the other two words in the 3-word paradigm, suggesting that stimulus relevance has an additional effect on P300 amplitude beyond rarity.     

Visual cognitive dysfunction in depression: an event-related potential study

The P3(00) event-related potentials (ERPs) elicited by visual stimuli in two visual tasks were assessed in depressed patients (12 patients with major depression and 11 patients with bipolar disorder) and compared with those of 20 age-matched normal controls. At remission, the ERPs from 18 of the depressed patients were again recorded. The visual oddball (VO) paradigm presented both target and standard visual stimuli and the simple visual (SV) paradigm presented a target but no standard visual stimulus. Subjects performed the VO task significantly less accurately than the SV task, as reflected by the behavioral measures (reaction-time and task accuracy). Depressed patients of the bipolar group showed longer P3 peak latency for the VO task and no change in P3 amplitude. No significant differences were found in any other ERP component between the groups. During remission, slowing RTs and reduced P3 peak latencies were observed for both major depression and bipolar disorder groups. Thus, the P3 ERP may be an index of the contribution of the slowed central processing to psychomotor retardation in clinically homogenous samples of depressive patients performing an appropriately demanding task.     

P300 from a single-stimulus paradigm: passive versus active tasks and stimulus modality

The P300 component of the event-related brain potential (ERP) was elicited with auditory and visual stimuli in separate experiments. Each study compared an oddball paradigm that presented both target and standard stimuli with a single-stimulus paradigm that presented a target but no standard stimuli. Subjects were instructed in different conditions either to ignore the stimuli, press a response key to the target, or maintain a mental count of the targets. For the passive ignore conditions, P300 amplitude from the single-stimulus paradigm was larger than that from the oddball paradigm. For the active tasks, P300 amplitude from the oddball paradigm was larger than that from the single-stimulus paradigm. For the press and count conditions, P300 amplitude and latency were highly similar for the oddball and single-stimulus procedures. The findings suggest that the single-stimulus paradigm can provide reliable cognitive measures in clinical/applied testing for both passive and active response conditions.     

Sensory and cognitive components of the CO2 laser evoked cerebral potential

We recorded CO₂ laser evoked cerebral potentials in 6 healthy subjects using both a standard technique and an oddball paradigm. In the standard technique stimuli were aimed at the dorsum of the left hand with the subject passive; in the oddball paradigm, target infrequent stimuli (P = 0.15) were directed to one side of the dorsum of the left hand and the subject was instructed to count their occurrence, the frequent stimulus being delivered to the other side of the hand. In both standard and oddball frequent recordings, CO₂ laser evoked potentials were a well-formed negative-positive complex with a peak latency and amplitude around 305 msec (to positivity) and 32 μV respectively. However, in the oddball target task a later potential was also recorded, with a mean latency and amplitude of 621 msec and 24 μV respectively which we believe to be a laser oddball potential. These results demonstrate that the CO₂ potential is not altered by manipulations of attention to any significant extent and suggests that it is therefore closely related to the primary sensory input. They also provide further evidence of the non-specificity of the oddball potential across sensory modalities.     

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.     

Prediction of Auditory and Visual P300 Brain-Computer Interface Aptitude

Objective

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for patients with late-stage motoneuron disease (e.g., amyotrophic lateral sclerosis (ALS)) or otherwise motor impaired people and are also used for motor rehabilitation in chronic stroke. Differences in the ability to use a BCI vary from person to person and from session to session. A reliable predictor of aptitude would allow for the selection of suitable BCI paradigms. For this reason, we investigated whether P300 BCI aptitude could be predicted from a short experiment with a standard auditory oddball.

Methods

Forty healthy participants performed an electroencephalography (EEG) based visual and auditory P300-BCI spelling task in a single session. In addition, prior to each session an auditory oddball was presented. Features extracted from the auditory oddball were analyzed with respect to predictive power for BCI aptitude.

Results

Correlation between auditory oddball response and P300 BCI accuracy revealed a strong relationship between accuracy and N2 amplitude and the amplitude of a late ERP component between 400 and 600 ms. Interestingly, the P3 amplitude of the auditory oddball response was not correlated with accuracy.

Conclusions

Event-related potentials recorded during a standard auditory oddball session moderately predict aptitude in an audiory and highly in a visual P300 BCI. The predictor will allow for faster paradigm selection.

Significance

Our method will reduce strain on patients because unsuccessful training may be avoided, provided the results can be generalized to the patient population.     

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.     

Laser-evoked potentials: exogenous and endogenous components

The aim of this study was to distinguish the exogenous component (related to the physical properties of the stimulus) and the endogenous component (reflecting event-related cognitive processing) of the laser-evoked potential (LEP). Short painful radiant heat pulses generated by a CO₂-laser were applied to the dorsum of the right and left foot. LEPs were recorded with 5 scalp electrodes in the midline versus linked earlobes in 26 healthy subjects. In order to identify the exogenous component, the LEP was recorded during a standardised distraction task (reading a short story). To identify the endogenous component P3 for the LEP, a 2-stimulus oddball paradigm was used (20% probability of targets). When the task of the oddball paradigm consisted of pressing a button, a movement-related long-latency negativity (N1200) was recorded in frontal leads that was absent in a counting task. The LEP of targets, frequent non-targets and during distraction was dominated by a single large positivity. The amplitude of this positivity was task-dependent and increased the more attention the subject payed to the laser stimuli (distraction < neutral < non-target < target). The laser-evoked positivity during distraction had a peak latency of about 400 msec (P400) and a maximum amplitude at the vertex, which was independent of inter-stimulus interval. The P3 following laser stimulation had a significantly later peak at about 570 msec (P570) and a different scalp topography with a parietal maximum. Its amplitude decreased when the interstimulus interval was reduced from 10 to 6 sec. Under neutral instructions, the LEP positivity consisted of a superposition of both the exogenous P400 and the endogenous P570.     

Temporal characteristics of triggering dipole sources of the auditory <Emphasis Type="Italic">P</Emphasis>300 in tasks varying in complexity

The localization and the order of triggering of the equivalent dipole sources of the auditory evoked potential (AEP) P300 component were analyzed in healthy subjects performing tasks that required different degrees of concentration. The AEP P300 was isolated and analyzed in 12 subjects aged 18–23 years. The P300 was recorded via 19 channels in mono- and bimodal tasks using two- and three-stimulus methods of the oddball paradigm. Analysis of the equivalent dipole sources of the P300 component upon hearing sounds showed simultaneous activity of dipole sources located in the temporal areas of both hemispheres and in the right frontal area, as well as in the brainstem, irrespective of the task’s complexity. The counting of sounds in the monomodal task was accompanied by consecutive involvement of the left temporal, right temporal, and left frontal sources in the P300 generation; in the bimodal task, these were, respectively, the left parietal, right temporal and hippocampal, and left frontal sources.     

Prediction of P300 BCI Aptitude in Severe Motor Impairment

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for persons with severe motor impairments. Previous studies have shown that the aptitude with which a BCI can be controlled varies from person to person. A reliable predictor of performance could facilitate selection of a suitable BCI paradigm. Eleven severely motor impaired participants performed three sessions of a P300 BCI web browsing task. Before each session auditory oddball data were collected to predict the BCI aptitude of the participants exhibited in the current session. We found a strong relationship of early positive and negative potentials around 200 ms (elicited with the auditory oddball task) with performance. The amplitude of the P2 (r  =  −0.77) and of the N2 (r  =  −0.86) had the strongest correlations. Aptitude prediction using an auditory oddball was successful. The finding that the N2 amplitude is a stronger predictor of performance than P3 amplitude was reproduced after initially showing this effect with a healthy sample of BCI users. This will reduce strain on the end-users by minimizing the time needed to find suitable paradigms and inspire new approaches to improve performance.     

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.     

Neuronal Correlates of a Virtual-Reality-Based Passive Sensory P300 Network

P300, a positive event-related potential (ERP) evoked at around 300 ms after stimulus, can be elicited using an active or passive oddball paradigm. Active P300 requires a person’s intentional response, whereas passive P300 does not require an intentional response. Passive P300 has been used in incommunicative patients for consciousness detection and brain computer interface. Active and passive P300 differ in amplitude, but not in latency or scalp distribution. However, no study has addressed the mechanism underlying the production of passive P300. In particular, it remains unclear whether the passive P300 shares an identical active P300 generating network architecture when no response is required. This study aims to explore the hierarchical network of passive sensory P300 production using dynamic causal modelling (DCM) for ERP and a novel virtual reality (VR)-based passive oddball paradigm. Moreover, we investigated the causal relationship of this passive P300 network and the changes in connection strength to address the possible functional roles. A classical ERP analysis was performed to verify that the proposed VR-based game can reliably elicit passive P300. The DCM results suggested that the passive and active P300 share the same parietal-frontal neural network for attentional control and, underlying the passive network, the feed-forward modulation is stronger than the feed-back one. The functional role of this forward modulation may indicate the delivery of sensory information, automatic detection of differences, and stimulus-driven attentional processes involved in performing this passive task. To our best knowledge, this is the first study to address the passive P300 network. The results of this study may provide a reference for future clinical studies on addressing the network alternations under pathological states of incommunicative patients. However, caution is required when comparing patients’ analytic results with this study. For example, the task presented here is not applicable to incommunicative patients.     

The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fields

There is some evidence to suggest that exposure to mobile phones (MPs) can affect neural activity, particularly in response to auditory stimuli. The current investigation (n = 120) aimed to test recent findings in this area, namely that N100 amplitude and latency would decrease, and that P300 latency and reaction time (RT) would increase under active relative to sham exposure during an auditory task. Visual measures were also explored. A double blind, counterbalanced, crossover design was employed where subjects attended two sessions 1 week apart. In both sessions participants (1) performed auditory and visual oddball tasks while electroencephalogram (EEG) was recorded with a MP set to sham exposure mounted over the temporal region, and (2) performed the same tasks while the handset was set to active/sham. When active, the MP transmitted for 30 min at 895 MHz (average power 250 mW, pulse modulated at 217 Hz, average SAR 0.11 W/kg). Paired t-tests compared difference scores from the sham/sham session to those from the sham/active condition. The study was designed to detect differences of 1\4 of a standard deviation with a power of 0.80. There was no significant difference between exposure conditions for any auditory or visual event related potential (ERP) component or RT. As previous positive findings were not replicated, it was concluded that there is currently no evidence that acute MP exposure affects these indices of brain activity.     

Amplitude-time parameters of long-latency components (N1, N2 and P300) of acoustic evoked potential of healthy examinees of young and mature age

The aim of study was to track a cumulative changes of amplitude-time parametres of components N1, N2 and P300 of acoustic evoked potential in experimental situations different in complexity (at the account and listening of sounds) and to compare the received distinctions at examinees of young and mature age. ERP were recorded at 12 healthy subjects from 18 to 22 ages and 12 subjects from 32 to 59 ages. The two-stimuli oddball paradigm was used. It is revealed that components N1, N2 and P300 recorded in the situation of the listenings of sounds without any preliminary instruction do not differ at persons of young and mature age. At examinees of younger age the biger amplitude of component N1 is noted at the account of sounds in comparison with listening whereas the latency of the one do not change depending on complexity of the task. It is shown that component N2 has stability of latency in relation to age and an experimental situation. The amplitude of component N2 is above at the account of sounds in both age groups. The amplitude-time parametres of component P300 do not differ at examinees of different age in a problem of listening of sounds. The revealed features of components N1, N2 and P300 at examinees of young and mature age in experimental situations different in complexity, allow to assume that with the years at the person adaptive mechanisms which allow carrying out successfully of the task.     

Target and Non-Target Processing during Oddball and Cyberball: A Comparative Event-Related Potential Study

The phenomenon of social exclusion can be investigated by using a virtual ball-tossing game called Cyberball. In neuroimaging studies, structures have been identified which are activated during social exclusion. But to date the underlying mechanisms are not fully disclosed. In previous electrophysiological studies it was shown that the P3 complex is sensitive to exclusion manipulations in the Cyberball paradigm and that there is a correlation between P3 amplitude and self-reported social pain. Since this posterior event-related potential (ERP) was widely investigated using the oddball paradigm, we directly compared the ERP effects elicited by the target (Cyberball: “ball possession”) and non-target (Cyberball: “ball possession of a co-player) events in both paradigms. Analyses mainly focused on the effect of altered stimulus probabilities of the target and non-target events between two consecutive blocks of the tasks. In the first block, the probability of the target and non-target event was 33% (Cyberball: inclusion), in the second block target probability was reduced to 17%, and accordingly, non-target probability was increased to 66% (Cyberball: exclusion). Our results indicate that ERP amplitude differences between inclusion and exclusion are comparable to ERP amplitude effects in a visual oddball task. We therefore suggest that ERP effects–especially in the P3 range–in the Oddball and Cyberball paradigm rely on similar mechanisms, namely the probability of target and non-target events. Since the simulation of social exclusion (Cyberball) did not trigger a unique ERP response, the idea of an exclusion-specific neural alarm system is not supported. The limitations of an ERP-based approach will be discussed.     

CHRNA5 variants moderate the effect of nicotine deprivation on a neural index of cognitive control

Individuals with reduced attention and memory cognitive control‐related processes may be motivated to smoke as a result of the cognitive enhancing effects of nicotine. Further, nicotine deprivation‐induced reductions in cognitive control may negatively reinforce smoking. Minor allele carriers at rs16969968 in the nicotinic acetylcholine receptor α5 subunit gene (CHRNA5) have been shown to exhibit both reduced cognitive control and greater nicotine dependence. It is therefore of interest to see if variants in this gene moderate the influence of nicotine deprivation on cognitive control. P3b and P3a components of the event‐related brain potential waveform evoked by a three‐stimulus visual oddball task are widely viewed as positive indices of cognitive control‐related processes. We tested the hypothesis that individuals possessing at least one minor allele at rs16969968 in CHRNA5 would show greater nicotine deprivation‐induced reductions in P3b and P3a amplitude. The sample included 72 non‐Hispanic, Caucasian heavy smokers (54 men and 18 women) with a mean age of 36.11 years (SD = 11.57). Participants completed the visual oddball task during counterbalanced nicotine and placebo smoking sessions. Findings indicated that rs16969968 status did not moderate nicotine effects on P3b or P3a, whereas variation in other CHRNA5 polymorphisms, which are not as well characterized and are not in linkage disequilibrium with rs16969968, predicted nicotine deprivation‐induced reduction of P3a amplitude: rs588765 (F_1,68 = 7.74, P = 0.007) and rs17408276 (F_1,67 = 7.34, P = 0.009). Findings are interpreted in the context of vulnerability alleles that may predict nicotine effects on cognitive control.     

Amplitude-time characteristics of the long-latency components (<Emphasis Type="Italic">N</Emphasis>1, <Emphasis Type="Italic">N</Emphasis>2, and <Emphasis Type="Italic">P</Emphasis>300) of acoustic evoked potential in healthy subjects

The aim of the study was to trace the cumulative changes in the amplitude-time parameters of the AEP (acoustic evoked potential) components N1, N2, and P300 in the experimental situations of different complexities (counting and listening to sounds) and to compare the differences between young and mature subjects. The AEP was recorded in 12 healthy subjects aged 18 to 22 years and in 12 subjects aged 32 to 59 years. It was revealed that the components N1, N2, and P300 recorded in the situation of listening without any preliminary instruction did not differ in young and mature individuals. In the younger subjects, a higher N1 amplitude was revealed when they counted sounds, compared to listening, whereas the latency values of this component did not differ, irrespective of the complexity of the task. The component N2 was shown to demonstrate latency stability in relation to the age and the experimental situation. The N2 amplitude was higher in the situation of counting sounds in both age groups. The amplitude-time parameters of P300 did not differ in subjects of different ages in the listening task. The features of the components N1, N2, and P300 revealed in young and mature subjects in the experimental situations differing in complexity lead us to suggest that, with age, humans develop adaptive mechanisms contributing to successful task performance.