P300 Waveform Research Articles

A comparison study of two P300 speller paradigms for brain–computer interface

In this paper, a comparison of two existing P300 spellers is conducted. In the first speller, the visual stimuli of characters are presented in a single character (SC) paradigm and each button corresponding to a character flashes individually in a random order. The second speller is based on a region-based (RB) paradigm. In the first level, all characters are grouped and each button corresponding to a group flashes individually in a random order. Once a group is selected, the characters in it will appear on the flashing buttons of the second level for the selection of desired character. In a spelling experiment involving 12 subjects, higher online accuracy was obtained on the RB paradigm-based P300 speller than the SC paradigm-based P300 speller. Furthermore, we analyzed P300 detection performance, the P300 waveforms and Fisher ratios using the data collected by the two spellers. It was found that the stimuli display paradigm of the RB speller enhances P300 potential and is more suitable for P300 detection.

Auditory P300: Selective Attention to 2 KHZ Tone-Bursts in Patients with Idiopathic Subjective Tinnitus

Objective: To study whether a group of idiopathic subjective tinnitus (IST) has abnormal changes in auditory P300 and to compare these results with normal subjects. Design: AuditoryP300 was done to thirty two patients with idiopathic subjective tinnitus and they were compared to normal. The elicited auditory P300 event-related potentials (ERPs) were analyzed in terms of peak amplitude and latency of the P300 waveforms. Basic audiological assessments that include pure tone audiometry and immittancemetry were done to the whole study group. Results: The results showed that while P300 peak amplitudes were overall reduced for idiopathic subjective tinnitus but it was varied individually and the P300 peak latencies were statistically of non-significant values between the study group and normal subjects. Discussion and Conclusion: Reduced waveform amplitudes were observed in IST than normal subjects. Possible mechanisms include that the processing of selective attention and its response to auditory tone burst stimuli associated with IST differ than that of the normal. The findings of our study are consistent with the hypothesis that IST patients differ in their response to auditory stimulus measured by P300 mainly auditory cortical area than normal subjects.

Possible Association of the GSK3β Gene with the Anxiety Symptoms of Major Depressive Disorder and P300 Waveform

Glycogen synthase kinase-3β (GSK3β) may play an important role in the brain of patients with major depressive disorder (MDD); therefore, we investigated whether the GSK3β gene is involved in the etiology of MDD and whether it affects MDD endophenotypes. Three single-nucleotide polymorphisms (SNPs) (rs6438552, rs7633279, and rs334558) were genotyped in 559 MDD patients and 486 healthy controls. To explore quantitative traits of MDD, we analyzed the association of these SNPs with the factor scores of the 17-item Hamilton Depression Rating Scale (HAMD-17) and the Hamilton Anxiety Rating Scale (HAMA). We also determined the effects of these SNPs on the measurement of the P300 wave. Although no significant association between GSK3β SNPs and MDD was found, some genotypes and haplotypes were associated with anxiety symptoms in MDD. The three SNPs were associated with the HAMA total score and with the HAMD anxiety and somatization factor score (p<0.05). Three-locus haplotype analysis showed the C-T-G carriers to have a strong association with the HAMA total score (p=0.032). Moreover, the P300 latency and amplitude were also associated with GSK3β genotypes. The individuals with the T allele genotype, both in rs6438552 and rs7633279, have a longer P300 latency than those carrying the C/C (p=0.04) and A/A genotype (p=0.013). The individuals with the G/G genotype in rs334558 have a lower amplitude than those carrying the A allele genotype (p=0.007). Our findings show, for the first time, that GSK3β polymorphisms may play an important role in MDD endophenotypes, especially in anxiety symptoms.

Electrophysiologic assessment of (central) auditory processing disorder in children with non-syndromic cleft lip and/or palate

Cleft of the lip and/or palate is a common congenital craniofacial malformation worldwide, particularly non-syndromic cleft lip and/or palate (NSCL/P). Though middle ear deficits in this population have been universally noted in numerous studies, other auditory problems including inner ear deficits or cortical dysfunction are rarely reported. A higher prevalence of educational problems has been noted in children with NSCL/P compared to craniofacially normal children. These high level cognitive difficulties cannot be entirely attributed to peripheral hearing loss. Recently it has been suggested that children with NSCLP may be more prone to abnormalities in the auditory cortex. The aim of the present study was to investigate whether school age children with (NSCL/P) have a higher prevalence of indications of (central) auditory processing disorder [(C)APD] compared to normal age matched controls when assessed using auditory event-related potential (ERP) techniques. School children (6 to 15 years) with NSCL/P and normal controls with matched age and gender were recruited. Auditory ERP recordings included auditory brainstem response and late event-related potentials, including the P1-N1-P2 complex and P300 waveforms. Initial findings from the present study are presented and their implications for further research in this area — and clinical intervention — are outlined.

A Novel Concealed Information Test Method Based on Independent Component Analysis and Support Vector Machine

The concealed information test (CIT) has drawn much attention and has been widely investigated in recent years. In this study, a novel CIT method based on denoised P3 and machine learning was proposed to improve the accuracy of lie detection. Thirty participants were chosen as the guilty and innocent participants to perform the paradigms of 3 types of stimuli. The electroencephalogram (EEG) signals were recorded and separated into many single trials. In order to enhance the signal noise ratio (SNR) of P3 components, the independent component analysis (ICA) method was adopted to separate non-P3 components (i.e., artifacts) from every single trial. In order to automatically identify the P3 independent components (ICs), a new method based on topography template was proposed to automatically identify the P3 ICs. Then the P3 waveforms with high SNR were reconstructed on Pz electrodes. Second, the 3 groups of features based on time,frequency, and wavelets were extracted from the reconstructed P3 waveforms. Finally, 2 classes of feature samples were used to train a support vector machine (SVM) classifier because it has higher performance compared with several other classifiers. Meanwhile, the optimal number of P3 ICs and some other parameter values in the classifiers were determined by the cross-validation procedures. The presented method achieved a balance test accuracy of 84.29% on detecting P3 components for the guilty and innocent participants. The presented method improves the efficiency of CIT in comparison with previous reported methods.

Effect of Caffeine on Evoked Potentials

Back ground: Caffeine a white crystalline xanthine alkaloid is the most widely used psychoactive stimulant in the world. Inspite of being used as a substance of abuse, it is widely used as a CNS and metabolic stimulant for its short term and long term pharmacological action. A number of studies with dramatic results have proved that caffeine is a stimulant. Review of literature: Effects of caffeine have been studied on brain function and behavior using number of tests, but, however, studies on acute effects of caffeine on both visual and auditory evoked potentials are few. Aim of the study: To record the effect of caffeine in relation with the auditory and visual evoked potentials, as well as to highlight the individual differences in its effects in variation with age, sex and substance abuse. Materials and Method : 6 healthy volunteers were recruited for the study after a questionnaire analysis followed by routine ophthalmologic and auditory examinations. They were administered 2mg/kg body weight of caffeine (PO) after 12hr abstinence from caffeine in any form. Auditory and visual evoked potentials were recorded before and after 30 minutes of ingestion of caffeine by using RMS Polyrite. Latency and amplitude of P100 in VEP and absolute latency and amplitude, inter-peak latencies in BAEP were evaluated. Results and conclusion: The data obtained revealed the decrease in the latencies of P100 waveform in VEP and I-V inter-peak latency in BAEP as well, indicating that caffeine improves transmission in the peripheral and central brain auditory pathways. Keywords - caffeine, evoked potential, age variation, sex variation, substance abuse.

Effect of DISC1 on the P300 Waveform in Psychosis

Abnormalities in the neurophysiological measures P300 amplitude and latency constitute endophenotypes for psychosis. Disrupted-in-Schizophrenia-1 (DISC1) has been proposed as a promising susceptibility gene for schizophrenia, and a previous study has suggested that it is associated with P300 deficits in schizophrenia. We examined the role of variation in DISC1 polymorphisms on the P300 endophenotype in a large sample of patients with schizophrenia or psychotic bipolar disorder (n = 149), their unaffected relatives (n = 130), and unrelated healthy controls (n = 208) using linear regression and haplotype analysis. Significant associations between P300 amplitude and latency and DISC1 polymorphisms/haplotypes were found. Those homozygous for the A allele of single-nucleotide polymorphism (SNP) rs821597 displayed significantly reduced P300 amplitudes in comparison with homozygous for the G allele (P = .009) and the heterozygous group (P = .018). Haplotype analysis showed a significant association for DISC1 haplotypes (rs3738401|rs6675281|rs821597|rs821616|rs967244|rs980989) and P300 latency. Haplotype GCGTCG and ACGTTT were associated with shorter latencies. The P300 waveform appears to be modulated by variation in individual SNPs and haplotypes of DISC1. Because DISC1 is involved in neurodevelopment, one hypothesis is that disruption in neural connectivity impairs cognitive processes illustrated by P300 deficits observed in this sample.

Impact of Spatial Filters During Sensor Selection in a Visual P300 Brain-Computer Interface

A challenge in designing a Brain-Computer Interface (BCI) is the choice of the channels, e.g. the most relevant sensors. Although a setup with many sensors can be more efficient for the detection of Event-Related Potential (ERP) like the P300, it is relevant to consider only a low number of sensors for a commercial or clinical BCI application. Indeed, a reduced number of sensors can naturally increase the user comfort by reducing the time required for the installation of the EEG (electroencephalogram) cap and can decrease the price of the device. In this study, the influence of spatial filtering during the process of sensor selection is addressed. Two of them maximize the Signal to Signal-plus-Noise Ratio (SSNR) for the different sensor subsets while the third one maximizes the differences between the averaged P300 waveform and the non P300 waveform. We show that the locations of the most relevant sensors subsets for the detection of the P300 are highly dependent on the use of spatial filtering. Applied on data from 20 healthy subjects, this study proves that subsets obtained where sensors are suppressed in relation to their individual SSNR are less efficient than when sensors are suppressed in relation to their contribution once the different selected sensors are combined for enhancing the signal. In other words, it highlights the difference between estimating the P300 projection on the scalp and evaluating the more efficient sensor subsets for a P300-BCI. Finally, this study explores the issue of channel commonality across subjects. The results support the conclusion that spatial filters during the sensor selection procedure allow selecting better sensors for a visual P300 Brain-Computer Interface.

Gaze independent brain–computer speller with covert visual search tasks

Objective Brain–computer interface (BCI) provides a mean of communication for the patients that are severely disabled by neuromuscular diseases. The performance of the classical P300 speller, however, declines noticeably in the gaze fixation condition. The speller paradigm presented in this paper aims to release the gaze dependency at the cost of an extra covert visual search task. Methods Clusters of characters were presented sequentially in the near-central vision as stimulation. Participants fixed their gaze on the center, searched and recognized the target character with covert shift of attention. Random position (RP) and fixed position (FP) presentation modes designed with different searching set size (6 for RP, and ⩽2 for FP) were examined. Results Online sessions using 10 stimulus sequences achieved character accuracies of 94.4% and 96.3% for RP and FP mode, respectively. For offline overall evaluation, the peak written symbol rate (WSR) of 1.38 symbols/min was obtained, with corresponding accuracies of 87.8% (RP) and 84.1% (FP). The P300 waveform of RP mode has evident longer latency and larger amplitude. Electrooculogram (EOG) analysis indicated that the performance was independent of gaze shift. Conclusions The proposed speller could be operated effectively and gaze independently by healthy participants. Significance The proposed gaze independent BCI approach promises reasonable communication capability for the profoundly paralyzed patients with head or ocular motor impairments.

A polymorphism in the microRNA-30e precursor associated with major depressive disorder risk and P300 waveform

Background Growing evidence shows that the etiological causes and pathological processes underlying major depressive disorder (MDD) and schizophrenia (SCZ) overlap. Our previous study revealed a strong association between the polymorphism ss178077483 in the miRNA-30e precursor (pre-miR-30e) and the risk of SCZ. We thus hypothesized that this SCZ risk allele at the pre-miR-30e gene also confers risk of MDD. Methods To explore the relationship between miR-30e ss178077483 and MDD, we conducted an association analyses in 1088 MDD patients and 1102 control subjects from the Han Chinese population. We also determined the effects of miR-30e ss178077483 on the development of P300 event-related potential components induced by an auditory odd-ball task. Results We detected a statistically significant positive association between miR-30e ss178077483 and MDD (allelic P = 0.0287; genotypic P = 0.0275). Moreover, the P300 latency was associated with miR-30e ss178077483 genotypes and the individuals with the C/T genotype have a longer P300 latency than those carrying the C/C genotype ( P = 0.009). Limitations Larger numbers of subjects and different ethnic groups would confirm and strengthen these preliminary findings. Conclusions To our knowledge, this is the first evidence to suggest that miRNA polymorphisms may play an important role in MDD susceptibility. These findings also imply that certain miRNAs may be involved in the etiology of MDD.

Increased psychophysiological parameters of attention in non-psychotic individuals with auditory verbal hallucinations

Objective Schizophrenia is associated with aberrant event-related potentials (ERPs) such as reductions in P300, processing negativity and mismatch negativity amplitudes. These deficits may be related to the propensity of schizophrenia patients to experience auditory verbal hallucinations (AVH). However, AVH are part of extensive and variable symptomatology in schizophrenia. For this reason non-psychotic individuals with AVH as an isolated symptom provide an excellent opportunity to investigate this relationship. Methods P300 waveforms, processing negativity and mismatch negativity were examined with an auditory oddball paradigm in 18 non-psychotic individuals with AVH and 18 controls. Results P300 amplitude was increased in the AVH group as compared to controls, reflecting superior effortful attention. A trend in the same direction was found for processing negativity. No significant differences were found for mismatch negativity. Conclusion Contrary to our expectations, non-psychotic individuals with AVH show increased rather than decreased psychophysiological measures of effortful attention compared to healthy controls, refuting a pivotal role of decreased effortful attention in the pathophysiology of AVH.

Follow up of P1 peak amplitude and peak latency in a group of specific language-impaired children

This project investigated the maturation of P1 of 32 native Arabic speaking children; all had a primary diagnosis of SLI. The study group had a mean age 60.25 (+/-6.4) months (range 50-80 months) at the time of the primary diagnosis. The control group consisted of 69 children matched for age, language level and academic skills, with no history of language disability. 30 children of the SLI group were re-examined 28 months after primary diagnosis. The test battery included basic audiological evaluation and P(1)/N(2) complex evoked by speech syllable /da/ and presented binaurally through sound field. Stepwise regression analysis of variables showed significant shortening of P1 peak latency in both control and SLI group showed proportional to the natural logarithm of the chronological age (r=-.414 &r(2)=.418). P1 peak amplitude showed significant decrease in amplitude in both control and SLI group proportional to the square of the chronological age (r=-.375 & r(2)=.140). However, no significant difference could be detected between the SLI group and the control group as regards P1 peak latency and peak amplitude. Moreover, the study showed no statistical significant difference between the control group and the study group as regards the correlation between P1 and language age (P1 latency t=.153, while significant t=.879 and P1 amplitude (t=-.37) significant t=.712). The partial correlation coefficient was .04 for P1 latency and .088 for P1 amplitude. Considering the heterogeneity of the SLI group, P1 peak amplitude and peak latency may be valuable to follow up the maturation of the auditory system on individual basis rather than for differential diagnosis of SLI patient from normal. P1 does not show dramatic developmental change in the age range 5-10 years to be used clinically. Further researches are needed to standardize statistical method for analyzing P1 waveform.

Prospective, cross-sectional study, demonstrating efficacy of blue fixation target while recording Pattern Visual Evoked Potential in optic neuropathy

To report the efficacy of a blue fixation target to record Pattern Visual Evoked Potential (PVEP) in optic neuropathy subjects with acquired red-green (RG) color vision deficit. This is a prospective, nonrandomized, cross-sectional, case series of twenty-nine eyes of twenty-two subjects with optic neuropathy of various etiologies. All underwent detailed ophthalmological evaluation, imaging, and PVEP. PVEP was done with 120' and 60' checker stimulus to both red and blue fixation targets. The amplitude and latency of P100 waveform was the measured outcome. The PVEP recording to blue fixation target was found to be superior to the red fixation target in cases of RG color vision deficits with both 120' (P = 0.01) and 60' (P = 0.037) check sizes. In the cases in which the PVEP was recordable with both red and blue fixation targets, the P100 amplitude and latency parameters were comparable and showed positive correlation. Defective fixation and abnormal RG color vision also affected PVEP recordability to the red fixation target. Good fixation is essential for obtaining a reliable PVEP recording. In this study, the authors have used a blue fixation target as a method to ensure fixation in patients with RG color deficits and have demonstrated the ability to get good recordings in cases with otherwise flat recording. The use of alternate colored target or achromatic fixation target should be considered to ensure good central fixation so as to yield better quality recording that possibly correlates better with the functioning of the optic pathway in subjects with abnormal color vision.

Comparisons of P300s from Standard Oddball and Omitted Paradigms: Implications to Exogenous/Endogenous Contributions

To compare the amplitude, latency, morphology, and threshold of the auditory P300 using standard oddball and omitted paradigms. P300 waveforms were measured from the Cz electrode site. Frequent stimuli for both paradigms were 1000 Hz tone bursts. Target stimuli for the standard oddball paradigm were 2000 Hz tone bursts and an omitted stimulus, or silent gap, for the omitted paradigm. Fifteen bilaterally normal-hearing young adults. There were significantly lower amplitudes, poorer morphology, and higher thresholds for the P300 using an omitted paradigm compared to the standard oddball paradigm. These results suggest that the auditory P300 could have a larger exogenous component than traditionally thought.

Compromised sensitivity to monetary reward in current cocaine users: An ERP study

We studied modulation of the P300 by monetary reward expected to be received on a sustained attention task in 18 individuals with current cocaine use disorders (CUD) and 18 control subjects. Results in the controls revealed sensitivity to money as measured with P300 amplitude and speed of behavioral response and their intercorrelations. In contrast, despite generally faster P300 waveforms and higher self-reported interest in the task, individuals with CUD did not display these responses to money versus nonreward; at the behavioral level, this impairment correlated with frequency of recent cocaine use. These preliminary results suggest a compromised sensitivity to a secondary reinforcer in CUD. This deficit, which needs to be replicated in larger samples of people with currently active versus abstaining CUD, may underlie the compromised ability to advantageously modify behavior in response to changing inner motivations and environmental contingencies.

EEG components of spontaneous trait inferences

Can event-related electro-encephalogram (EEG) responses provide support for the occurrence of spontaneous trait inferences (STI)? Participants read sentences describing the behavior of a target person from which a strong trait could be inferred. The last word of each sentence determined the consistency with the trait induced during an introductory paragraph. In comparison with sentences that were consistent with the implied trait, when the sentences were inconsistent, an event-related P300 waveform was observed at parietal scalp regions (Pz). This dependency on behavioral consistency indicates that trait inferences were made spontaneously. Memory measures taken after the presentation of the stimulus material involved sentence completion and trait-cued recall, and also supported the occurrence of spontaneously inferred traits associated with the actor. Interestingly, increased memory for consistent relative to inconsistent behaviors at the trait-cued recall task was significantly correlated with the P300, which supports this latter measure as a valid neural correlate of spontaneous trait inferences.

Electrophysiological basis for the ability of olanzapine to improve verbal memory and functional outcome in patients with schizophrenia: A LORETA analysis of P300

Abnormality of P300 waveforms of event-related potentials (ERPs) has been suggested to represent an aspect of the pathophysiology of schizophrenia. Previous work points to the contribution of altered neural function in discrete brain regions in the left hemisphere to psychotic symptoms and cognitive deficits of schizophrenia. In this study, we sought to determine: 1) if patients with schizophrenia elicit a decreased P300 current source density in brain areas, such as the superior temporal gyrus (STG); 2) if decreased P300 generator density in the left STG is recovered by treatment with the most widely-used antipsychotic drug olanzapine; and 3) if the recovery of P300 source density is associated with improvements of cognitive and functional status. P300 in response to an auditory oddball task, as well as verbal learning memory, psychopathology, and quality of life were evaluated in 16 right-handed patients with schizophrenia before and after treatment with olanzapine for 6 months. ERP data were also obtained from 16 right-handed age and gender-matched normal volunteers. Low resolution electromagnetic tomography (LORETA) analysis was used to obtain current density images of P300. Patients with schizophrenia showed significantly smaller LORETA values in several brain regions in the left side, particularly STG, middle frontal gyrus, and precentral gyrus, compared with control subjects. Six-month treatment with olanzapine significantly increased P300 source density only in the left STG. Positive symptoms, negative symptoms, verbal learning memory, and quality of life were also improved during treatment. Significant correlations were found between the increase in LORETA values of left STG vs. improvements of negative symptoms, as measured by Scale for the Assessment of the Negative Symptoms, and verbal learning memory, as measured by the Japanese Verbal Learning Test. Improvement of quality of life, as evaluated by the Quality of Life Scale, were significantly associated with an increase in LORETA values of middle frontal gyrus, and tended to correlate with that of precentral gyrus. The results of this study suggest that changes in cortical activity, as measured by ERPs, are responsible for the ability of some antipsychotic drugs to improve cognition and functional outcome in patients with schizophrenia.

INDEPENDENT COMPONENT ANALYSIS OF EEG RECORDED DURING TWO-PERSON GAME PLAYING

We report a study on two-person game playing involving simultaneous EEG recording from both subjects. Independent component analysis is used to identify activities of individual cortical EEG sources. Activity of a midline fronto-central component is identified in four of five subjects. This component accounts for the P300 waveform whose amplitude varies, depending on the success in the gaming situation.

Voxel-based analysis of P300 electrophysiological topography associated with positive and negative symptoms of schizophrenia

Abnormal P300 waveforms of the event-related potentials during the auditory oddball task are one of the most consistent findings in patients with schizophrenia. In the present study, we sought to test the hypothesis that the abnormal P300 waveform results from composite representation of neural activity in anatomically distinct brain regions responsible for the manifestation of positive and negative symptoms. We used the low-resolution brain electromagnetic tomography (LORETA) to obtain current density images of the P300 component from 26 patients with schizophrenia. The statistical parametric mapping (SPM) was applied to the LORETA images in order to identify brain regions that are related with the severity of psychotic symptoms as evaluated by the Brief Psychiatric Rating Scale (BPRS). The BPRS Total score was negatively correlated with the P300 current density in the left superior temporal gyrus (r=−0.615, corrected p=0.009) and that in the right medial frontal region (r=−0.571, corrected p=0.019) by means of SPM single-subject covariates model. These brain regions were included in the region-specific P300 sources as represented by the current density maxima (corrected p<0.05) using SPM one-sample t-test. A subsequent region-of-interest analysis of Pearson correlations revealed specific relationships between the Positive subscale score and the mean current density in the left superior temporal gyrus (r=−0.528, p=0.005) and between the Negative subscale score and the mean current densities in the medial frontal region (r=−0.551, p=0.003) and left superior temporal gyrus (r=−0.499, p=0.009). These results indicate that functional disturbances of neural networks involving the medial prefrontal and superior temporal regions may be responsible for the generation of positive and the negative psychotic symptoms of schizophrenia.

Changes of Brain Potentials in Response to Smoking-Induced Stimuli in Smokers

Changes in P300 amplitude were used as an indicator of reactivity to smoking-related stimuli in smokers. The amplitude of P300--a component of event-related brain potentials (ERPs) elicited by 10 smoking-related (craving), 10 antismoking (aversive) and 10 neutral stimuli-- was recorded in smokers (n=10) and nonsmokers (n=10). Electroencephalography (EEG) data were obtained by the Laxtha EEG-monitoring device in the EEG recording room, and were recorded at F3, F4, C3, and C4. Three-way repeated-measures analysis of variance (ANOVA) was computed on the P300 amplitudes. The factors were group (smokers, nonsmokers), stimulus (craving, aversive, neutral), and electrode location (F3, F4, C3, and C4). The main effects of stimulus were significant, but the group effects did not show significant interactions with other factors. An interesting observation was the similarity between P300 waveforms for craving and aversive stimuli in smokers. These findings could indicate that the antismoking-related response is similar to the smoking-related one.