Generation Of Event-related Potentials Research Articles

Olfactory-induced brain activity in Parkinson's disease relates to the expression of event-related potentials: a functional magnetic resonance imaging study

Olfactory disorders are common in patients with idiopathic Parkinson's disease (IPD). In IPD patients with hyposmia olfactory event-related potentials (ERPs) are typically found to be delayed or absent. Altered ERPs in IPD patients may also be consistent with reduced neuronal activity in the medial temporal lobe following olfactory stimulation, as demonstrated by functional magnetic resonance imaging (fMRI). We analyzed ERPs and fMRI scans of hyposmic IPD patients ( n=18) to gain further insight about the brain regions involved in generation of olfactory ERPs. Patients were separated into two groups ( n=9 per group), based on the detectability (+) or non-detectability (−) of ERPs. Central activation during olfactory stimulation was examined using fMRI. Both ERP+ and ERP− patients showed activity in brain areas relevant to olfactory processing, such as the amygdala, parahippocampal regions, and temporal regions (BA 37, 21/22). Comparison of both groups revealed higher activation in ERP+ patients, especially in the amygdala, parahippocampal cortex, inferior frontal gyrus (BA 47), insula, cingulate gyrus, striatum, and inferior temporal gyrus. The relationship between the expression of olfactory ERPs and cortical activation patterns seen during olfactory stimulation in fMRI in IPD patients supports the idea that ERPs are a sensitive marker of neurodegeneration in olfactory regions. In accordance with current neuropathological staging concepts, olfactory ERPs may be reflecting pathological changes in olfactory regions, independent of the typically observed nigro-striatal degeneration in IPD. Reduced activation of primary olfactory areas in the ERP-group may reflect a severe disruption of olfactory processing in these patients.

Genetic determinants of target and novelty-related event-related potentials in the auditory oddball response

Processing of novel and target stimuli in the auditory target detection or ‘oddball’ task encompasses the chronometry of perception, attention and working memory and is reflected in scalp recorded event-related potentials (ERPs). A variety of ERP components related to target and novelty processing have been described and extensively studied, and linked to deficits of cognitive processing. However, little is known about associations of genotypes with ERP endophenotypes. Here we sought to elucidate the genetic underpinnings of auditory oddball ERP components using a novel data analysis technique. A parallel independent component analysis of the electrophysiology and single nucleotide polymorphism (SNP) data was used to extract relations between patterns of ERP components and SNP associations purely based on an analysis incorporating higher order statistics. The method allows for broader associations of genotypes with phenotypes than traditional hypothesis-driven univariate correlational analyses. We show that target detection and processing of novel stimuli are both associated with a shared cluster of genes linked to the adrenergic and dopaminergic pathways. These results provide evidence of genetic influences on normal patterns of ERP generation during auditory target detection and novelty processing at the SNP association level.

Impairment of source memory in patients with obsessive–compulsive disorder: Equivalent current dipole analysis

We examined memory performance and cortical source localization of old/new effects in a source memory task in obsessive–compulsive disorder (OCD) patients by employing an equivalent current dipole (ECD) model using EEG and a realistic head model. Event-related potentials (ERPs) were recorded while 14 OCD patients and 14 age-, sex-, handedness-, and educational level-matched healthy control subjects performed recognition tasks for spoken words (items) or for the voice of the speaker of spoken words (sources). In the item memory task, both groups showed ERP old/new effects at 300–700 ms. In the source memory task, the controls showed ERP old/new effects at 400–700 ms, whereas the OCD patients did not. Compared with the controls, the OCD patients showed significantly lower source accuracy and prolonged reaction times to the old words with accurate voice judgments. There were no differences between the OCD and control groups with regard to the locations of the ERP generators elicited by source correct and correct rejection conditions. The OCD patients showed significantly altered hemispheric asymmetry of ECD power in the frontal lobe during source memory retrieval, compared with the controls. These results indicate that OCD patients have preserved item memory about content, but impaired source memory about context.

Auditory target detection activates frontal and parietal cortices: Evidence from high gamma power and low-frequency phase coherence in the subdural electrocorticogram

Auditory target detection activates frontal and parietal cortices: Evidence from high gamma power and low-frequency phase coherence in the subdural electrocorticogram

The best of both worlds: Phase-reset of human EEG alpha activity and additive power contribute to ERP generation

Some authors have proposed that event-related potentials (ERPs) are generated by a neuronal response which is additive to and independent of ongoing activity, others demonstrated that they are generated by partial phase-resetting of ongoing activity. We investigated the relationship between event-related oscillatory activity in the alpha band and prestimulus levels of ongoing alpha activity on ERPs. EEG was recorded from 23 participants performing a visual discrimination task. Individuals were assigned to one of three groups according to the amount of prestimulus total alpha activity, and distinct differences of the event-related EEG dynamics between groups were observed. While all groups exhibited an event-related increase in phase-locked (evoked) alpha activity, only individuals with sustained prestimulus alpha activity showed alpha-blocking, that is, a considerable decrease of poststimulus non-phase-locked alpha activity. In contrast, individuals without observable prestimulus total alpha activity showed a concurrent increase of phase-locked and non-phase-locked alpha activity after stimulation. Data from this group seems to be in favor of an additive event-related neuronal response without alpha-blocking. However, the dissociable EEG dynamics of total and evoked alpha activities together with a complementary simulation analysis indicated a partial event-related reorganization of ongoing brain activity. We conclude that both partial phase-resetting and partial additive power contribute dynamically to the generation of ERPs. The prestimulus brain state exerts a prominent influence on event-related brain responses.

Selective anterior cingulate cortex deficit during conflict solution in schizophrenia: An event-related potential study

Background Schizophrenia research has gained a new focus on identification and further characterization of neurocognitive deficits in the search for behavioural endophenotypes of this disorder. The objective of this study was to explore differential cortical processing during executive control in schizophrenia as assessed with the attention network test (ANT). Methods Sixteen schizophrenic patients and sixteen healthy controls matched for gender, age, education, and nicotine consumption were tested with the ANT while recording 29-channel-electroencephalogram (EEG). Visual event-related potentials (ERP) N200 and P300 were topographically analyzed and cortical mapping using low resolution brain electromagnetic tomography (LORETA) was applied to localize neuroelectric generators of ERP. Results Behaviourally, significant differences between schizophrenic patients and controls were found only for the conflict condition ( p < 0.05) and for conflict adjusted by mean reaction time ( p < 0.01). Examining ERP of control subjects, N200 failed to show robust flanker congruency effects. P300 amplitude was reduced at Pz ( p < 0.05) and P300 latency was increased at Cz ( p < 0.005) for the conflict condition. Schizophrenic patients differed significantly in P300 latency at Cz during late conflict processing ( p < 0.005). Source analysis revealed a deficit in anterior cingulate cortex ( p < 0.05). Conclusion Our results are in line with previous reports about dysfunctional ACC activation in schizophrenia and argue in favour of a selective deficit of cortical conflict resolution. It is further proposed that dysfunctional ACC activation during executive processing may be a neurophysiologic endophenotype candidate of schizophrenia.

Alpha Phase Reset Contributes to the Generation of ERPs

An unresolved question in electroencephalogram (EEG) research is whether event-related potentials (ERPs) are generated by phase-reset or evoked response. We analyzed data of a visual feature detection task and will show 1) phase concentration in the alpha frequency range, 2) ongoing alpha activity prior to stimulus onset, 3) evoked alpha oscillation in the ERP, 4) lack of power increase during phase concentration, 5) decrease in amplitude variance during early evoked components preceding a decrease in power, and 6) the same cortical sources for induced prestimulus power and evoked poststimulus power. Because none of these data provide unequivocal evidence for phase reset, we additionally tested the basic assumption of the evoked model, which is the additivity of the evoked response on the basis of a simulation approach. Our findings suggest that nonadditive processes-typical for a phase reset-are involved in the generation of the ERP. Thus, together with the other findings this study provides unequivocal evidence for phase resetting in the human EEG.

Alpha rhythm of the EEG modulates visual detection performance in humans

The effects of the changes in the frequency spectrum of the electroencephalogram (EEG) on the perception of near-threshold visual stimuli and on the event-related potentials (ERPs) produced by these stimuli were investigated on 12 healthy volunteers. The stimulus intensity, at which each subject could detect 50% of the presented stimuli, was defined as the sensory threshold for that subject. Single ERP trials were separated into two groups: trials with detected and undetected stimuli. The ERPs and the average power spectra of the 1 s prestimulus periods were computed for both conditions. P300 amplitudes of the ERPs, and total power and relative band powers of the delta (0.5–4 Hz), theta (4–7.5 Hz), alpha (7.5–13 Hz), beta (13–30 Hz), and gamma (30–70 Hz) frequency bands of the prestimulus power spectra were measured. Between the two conditions, a specific difference was observed in the relative power of the alpha band, which was significantly lower before detected stimuli ( p<0.01) in line with significantly higher amplitudes of the ERPs ( p<0.001). These results show that short-lasting changes in brain's excitability state are reflected the relative alpha power of the EEG, which may explain significant variability in perceptual processes and ERP generation especially at boundary conditions such as sensory threshold.

Neural dynamics and the fundamental mechanisms of event-related brain potentials.

Event-related potentials (ERPs) provide a critical link between the hemodynamic response, as measured by functional magnetic resonance imaging, and the dynamics of the underlying neuronal activity. Single-trial ERP recordings capture the oscillatory activity that are hypothesized to underlie both communication between brain regions and amplified processing of behaviorally relevant stimuli. However, precise interpretations of ERPs are precluded by uncertainty about their neural mechanisms. One influential theory holds that averaged sensory ERPs are generated by partial phase resetting of ongoing electroencephalographic oscillations, while another states that ERPs result from stimulus-evoked neural responses. We formulated critical predictions of each theory and tested these using direct, intracortical analyses of neural activity in monkeys. Our findings support a predominant role for stimulus-evoked activity in sensory ERP generation, and they outline both logic and methodology necessary for differentiating evoked and phase resetting contributions to cognitive and motor ERPs in future studies.

Medial agranular cortex activity related to event-related potential generation in the rat

Neuronal firings and local field potentials were recorded in the medial agranular cortex (Fr2) together with surface event-related potentials (ERPs) during an auditory oddball task in the rat. 10/32 Fr2 neurons showed a sustained increase in firing frequency in response to target tone (100–615 ms from the tone onset) with an activation peak corresponding to surface P100 component. At the intra-cortical recording site, local P100 component was observed with greater peak amplitude than that on the surface. No conspicuous neuronal response was evoked by non-target tone. The results suggest that the rat Fr2 is involved in stimulus discrimination and generation of ERPs during the oddball task.

Auditory event-related potentials in patients with premature ejaculation

Objectives. To investigate in a descriptive manner the P300 component of the event-related potential (ERP), which is related to aspects of cognitive processing, in patients with premature ejaculation (PE) to determine whether there is a cognitive alteration in this condition. Recent studies with short latency evoked potentials such as cortical somatosensory evoked potentials have indicated that afferent sensory inputs from the genital area to the nervous system are increased in PE. However, the cortical neural process of ejaculation has remained poorly understood. Methods. We performed ERPs in 20 patients with PE and in 20 age-matched healthy subjects. ERPs were evoked by an auditory oddball paradigm consisting of 150 tone bursts (80% 1 kHz; 20% 2 kHz). The latencies of the N200 and the P300 waves and the amplitude of the P300 wave were measured. Results. The mean latencies of the N200 and P300 waves were significantly longer in the patients with PE than in the controls ( P <0.04 and <0.03, respectively). No significant difference was found in the P300 amplitude between the controls and patients ( P >0.05). Conclusions. These data indicate that the greater cortical representation of sensory stimuli from the genital areas that has been shown with somatosensory evoked potential studies might be related to a cognitive/neurobehavioral dysfunction. The dysfunction involves an increased time to evaluate and categorize the stimuli in the central nervous system, with no change in the quality of cognition and neural disinhibition by the prefrontal cortex to early sensory processing in subcortical or primary cortical regions, which are cognitive neural processes underlying ERP generation.

Electrophysiological analysis of cognitive slowing in subjects with mitochondrial encephalomyopathy

Mitochondrial encephalomyopathies (MEs) are multisystemic inherited disorders affecting tissues with high energy requirement such as the muscle, retina and central nervous system. Progressive external ophthalmoplegia and myopathy are the most common features in adults, and cognitive impairment is rare. In many neurodegenerative disorders, ERPs have been effectively performed to record cognitive slowing on tasks with different amount of information. To analyze the evidence for possible cognitive slowing, a standard auditory oddball paradigm with a button-press response was applied. Participants were 11 non-demented patients affected by mitochondrial encephalomyopathy and 14 age-matched normal controls. This hypothesis was tested using two tasks of different difficulty (pure tone vs. phonetic stimuli). Reaction time (RT), performance ( P) and event-related potentials (ERPs) were measured. RT and P were not significantly different between the groups. Patients showed significantly increased N2 latency and reduced P3 amplitude on both tasks. No difference was found in pure tone and phonetic task conditions. Results were interpreted as electrophysiological signs of cognitive slowing—particularly in relation to stimulus evaluation—irrespective of sensory problems, response selection and cognitive load. These findings suggest that in ME patients, there may be a possible dysfunction of neural mechanisms underlying cognitive events and ERP generation.

Neuronal firing activity in the dorsal hippocampus during the auditory discrimination oddball task in awake rats: relation to event-related potential generation

In order to investigate the roles of the hippocampus in event-related potential (ERP) generation, extracellular neuronal firings in the dorsal hippocampus were recorded together with the ERPs on the cortical surface and at the hippocampus during the auditory discrimination task in awake rats. The major ERP components on the cortical surface in response to the target tone were the P2, N2, and P3 with the latencies being approximately 100, 200 and 450 ms, respectively. For the non-target tone, the N2 and P3 components were not clearly observed. Local ERP at the hippocampus exhibited similar wave-forms to that on the cortex in response to the target and non-target tones. In the hippocampus, 11 of 21 neuronal firings showed a long-latency sustained activation from 113.6±89.7 ms to 539.1±208.6 ms with the peak being 281.6±167.4 ms after the target tone onset. This increase was not observed after the non-target tone, and was not prominent when the rat did not perform the task. It was not time-locked to lever pressing behavior, and was not affected by the intensity of the tone stimulus. These features in relation to behavioral and paradigm indices were similar to the long-latency ERP components, N2 and P3. Possible involvement of the hippocampus in ERP generation was further suggested by the correlation between the magnitude of the long-latency activation and the amplitudes of N2 and P3 in some hippocampal firings. On the other hand, seven neuronal firings showed a short-latency transient activation with the peak at 36.3±14.4 ms accompanied by the early components of local ERP in the hippocampus both after the target and non-target tones. This response was more conspicuous when the rat did not perform the task and its amplitude was positively affected by the stimulus intensity. These findings imply that there are two types of hippocampal neuronal activation during the auditory discrimination oddball task. One is the short-latency activation that is related to information processing of the exogenous stimulus property. The second is the long-latency activation that may be involved in execution of the cognitive task, and in generation of long-latency ERP components.

Dynamic changes of cognitive habituation and serotonin metabolism during the migraine interval.

Migraine patients show a specific cognitive processing with a loss of habituation in the interval and a normal habituation in the attack as measured by event-related potentials (ERPs). It is unknown whether the loss of habituation changes during the migraine interval or is a stable state. Serotonin (5HT) metabolism is involved in the pathophysiology of migraine and also in the generation of ERPs. We enrolled 14 patients with regular migraine attacks in order to measure visually evoked ERPs repetitively during the migraine interval and in the migraine attack. Cognitive habituation was evaluated by analysis of P3 latency. Platelet serotonin content and free serotonin plasma level were measured at the same time points. The loss of habituation increased continuously during the migraine interval and abruptly normalized in the migraine attack (p < 0.05, time series analysis). The platelet 5HT content decreased significantly in the migraine attack (p < 0.03) and was at its maximum in the middle of the interval. The P3 latency was significantly increased in the attack (p < 0.01) and was significantly inversely correlated with the platelet 5HT content (r = -0.44, p < 0.001). Free 5HT plasma levels did not show any significant change. Our findings suggest that loss of cognitive habituation continuously increases during the migraine interval until its normalization in the migraine attack. This phenomenon cannot be attributed to serotonergic transmission. In patients with regular changes of cognitive habituation before the migraine attack, it might be possible to predict the attack by analysing ERPs.

Diminished responsiveness of ERPs in schizophrenic subjects to changes in auditory stimulation parameters: implications for theories of cortical dysfunction

Event-related potentials (ERPs) were recorded from 15 schizophrenic patients and 17 normal controls in an auditory oddball paradigm in order to investigate the effects of stimulus probability and interstimulus interval (ISI) on deficits in mismatch negativity (MMN) generation in schizophrenia. MMN amplitude was reduced for schizophrenics overall, with the degree of deficit increasing as deviant probability decreased. In contrast, schizophrenic subjects were no more affected by alterations in ISI than controls. The experimental design also permitted evaluation of N1 generation as a function of ISI in schizophrenia. Schizophrenic subjects showed decreased N1 amplitude across conditions, with the degree of deficit increasing with increasing ISI. For both MMN and N1, therefore, the degree of deficit increased with increasing component amplitude in normals, implying that the deficit in ERP generation in schizophrenia may reflect a decrease in maximal current flow through underlying neuronal ensembles. The observed pattern of dysfunction is consistent both with observations of impaired precision of processing in schizophrenia, and with predictions of the PCP/NMDA model.

Demonstration of mismatch negativity in the monkey

In humans, deviant auditory stimuli elicit an event-related potential (ERP) component, termed “mismatch negativity” (MMN), that reflects the operation of a cortical detector of infrequent stimulus change. Epidural auditory ERPs were recorded from 3 cynomolgous monkeys in response to soft and loud clicks. “Oddball” loud or soft stimuli elicited a long-duration frontocentral negativity, peaking at approximately 85 msec, that was superimposed upon cortically generated obligatory ERP components. These data suggest that monkeys might serve as a heuristically valuable system in which to study the neurochemical and neuroanatomical substrates of early context-dependent ERP generation.

Myotonic Dystrophy: An Electrophysiological Study of Cognitive Deficits

Patients with Myotonic Dystrophy (MyD) frequently suffer from a dysfunction of the primary sensory pathways, as documented by abnormalities of short-latency evoked potentials. Impairment of intellectual functions has been less extensively investigated. Short-latency brainstem auditory evoked potentials (BAEPs) as well as long-latency auditory event-related potentials (ERPs) were recorded from 5 female and 6 male patients affected by MyD. A simple discrimination ("oddball") paradigm was used to record ERPs to tones from Fz, Cz, Pz. Both BAEPs and ERPs were significantly altered as compared to normals. BAEP abnormalities were detected in 9 patients and ERP components N2 and P3 were delayed or absent for all patients, who nonetheless correctly discriminated between tones. These data indicate that CNS dysfunction in MyD involves not only primary sensory systems but also neural mechanisms underlying cognitive events and ERP generation.

The intracranial topography of the P3 event-related potential elicited during auditory oddball

In order to isolate the anatomical locus of neural activity primarily responsible for generating the scalp-recorded P3 (or P300), the topography of event-related potentials (ERPs) elicited during an auditory oddball task was compared between medial-to-lateral aspects of the frontal, parietal, and temporal lobes in 10 epileptic patients undergoing stereoelectroencephalography for seizure localization. Evidence of local ERP generation was obtained from each of these areas. Small amplitude P3-type potentials were sometimes observed to invert polarity across recording contacts in the frontal lobe. Large amplitude positive polarity P3-type components were observed in the lateral neocortex of the inferior parietal lobule (IPL), that rapidly attenuated in amplitude at more anterior, posterior, superior, inferior, and medial recording contacts. Large amplitude polarity inverting P3-type components were also observed to be highly localized to hippocampal contacts of temporal lobe electrodes. These data are discussed in the context of other recent studies of lesion effects, scalp topography, and intracranial recordings, and it is concluded that activity generated in the IPL is likely to make the major contribution to the scalp-recorded P3, with smaller contributions from these other sources. Finally, salient topographical differences between the intracranial distribution of the P3 and those of the N2 (or N200) and slow wave (SW) suggest that the generators of these components are not identical.

Three-channel Lissajous′ trajectories of auditory event-related potentials to target stimuli

Three orthogonal recordings (‘X’, ‘Y’ and ‘Z’) of event-related potentials (ERPs) evoked by auditory target stimuli were represented in 3-dimensional voltage-space, to produce 3-channel Lissajous′ trajectories (3-CLTs). Stimuli were verbal or non-verbal and were differentiated by their pitch, phonemic or phonetic attributes. Visual inspection and quantitative evaluations unexpectedly revealed that the 3-CLT of these ERPs strongly resembles a ‘hair-pin’ trajectory. This trajectory tilted in space at characteristic angles with each of the analysis axes: 133° with the ‘X’ axis, 87° with the ‘Y’ axis, and 54° with the ‘Z’ axis. The relatively small inter-subject variability observed in the geometrical measures, particularly in orientation, may be attributed to the slight variation in the underlying generators. 3-CLT analysis could be useful in future clinical as well as source studies of ERP generators.

Amplitude as well as latency of the CO 2 evoked potential change under constant concentration but different stimulus durations

Some authors have proposed that event-related potentials (ERPs) are generated by a neuronal response which is additive to and independent of ongoing activity, others demonstrated that they are generated by partial phase-resetting of ongoing activity. We investigated the relationship between event-related oscillatory activity in the alpha band and prestimulus levels of ongoing alpha activity on ERPs. EEG was recorded from 23 participants performing a visual discrimination task. Individuals were assigned to one of three groups according to the amount of prestimulus total alpha activity, and distinct differences of the event-related EEG dynamics between groups were observed. While all groups exhibited an event-related increase in phase-locked (evoked) alpha activity, only individuals with sustained prestimulus alpha activity showed alpha-blocking, that is, a considerable decrease of poststimulus non-phase-locked alpha activity. In contrast, individuals without observable prestimulus total alpha activity showed a concurrent increase of phase-locked and non-phase-locked alpha activity after stimulation. Data from this group seems to be in favor of an additive event-related neuronal response without alpha-blocking. However, the dissociable EEG dynamics of total and evoked alpha activities together with a complementary simulation analysis indicated a partial event-related reorganization of ongoing brain activity. We conclude that both partial phase-resetting and partial additive power contribute dynamically to the generation of ERPs. The prestimulus brain state exerts a prominent influence on event-related brain responses.