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Event-related potentials (ERPs) evoked by light flashes and auditory tones in a standard odd-ball procedure were recorded from Fz, Cz and Pz scalp sites. Tonic pain was evoked by immersion of the hand in cold water (5 degrees C). Significant effects of pain were found in responses to target stimuli but not in responses to non-target stimuli. P300 wave was affected more than the earlier P200 component. The reduction of P300 amplitude was the strongest effect, both in auditory and visual tests. P300 latency was not significantly affected. Difference curves (target minus non-target ERPs) showed the additional effects: latency of P200 component was elongated and its amplitude enlarged but only in auditory experiments. In control experiments with warm water stimulation no significant alterations of P300 or P200 components were found. The results show that the effect of tonic pain is specific: it predominantly affects the processes that manifest themselves as amplitude changes of P300 components in responses to target stimuli.     

Mismatch negativity in the neurophysiologic/behavioral evaluation of auditory processing deficits: a case study

The subject of this case report is an 18-year-old woman with grossly abnormal auditory brain stem response (ABR), normal peripheral hearing, and specific behavioral auditory processing deficits. Auditory middle latency responses (MLRs) and cortical potentials N1, P2, and P300 were intact. The mismatch negativity (MMN) was normal in response to certain synthesized speech stimuli and impaired to others--consistent with her behavioral discrimination of these stimuli. Behavioral tests of auditory processing were consistent with auditory brain stem dysfunction. A neuropsychological evaluation revealed normal intellectual and academic performance. The subject was in her first year of college at the time of the evaluation. This case study is important because: (1) Although there have been several reports of absent/abnormal ABR with preserved peripheral hearing and deficits in auditory processing, little is known about the specific nature of the auditory deficits experienced by these individuals. Such information may be valuable to the clinical management of patients with this constellation of findings. (2) Of interest is the information that the mismatch negativity (MMN) cortical event-related potential can bring to the evaluation of patients with auditory processing deficits. The MMN reflects central auditory processing of small acoustic differences and may provide an objective measure of auditory discrimination. (3) From a theorectical standpoint, a patient with neural deficits affecting specific components of the auditory pathway provides insight into the relationship between evoked potentials and physiological mechanisms of auditory processing. How do various components of the auditory pathway contribute to speech discrimination? How might evoked potentials reflect the processes underlying the neural coding of specific features of speech stimuli such as timing and spectral cues?     

How to evaluate study methodology in published clinical research

Postmortem, magnetic resonance, and event-related potential studies suggest the presence of temporal lobe abnormalities in schizophrenia. Analyses using convergent measurements of brain structure and function, however, have rarely been done in the same patients. We recently developed a protocol using high-spatial-resolution magnetic resonance scans, auditory P300 event-related potentials, and thought disorder scales to examine temporal lobe structure and function in the same patients. We report a case of schizophrenia that showed left-lateralized volume reduction in the superior temporal gyrus, hippocampus, and parahippocampal gyrus (also on right), with associated P300 amplitude reduction and thought disorder marked by word-finding difficulties and perseverations.     

Input and central processing expressed in ERP and heart rate changes to rare target and rare nontarget stimuli

Whether late positive components of event-related potentials (ERPs) parallel changes in heart rate (HR) indicative of attention/orienting to rare stimuli has been debated. In the present study, a three-stimulus design was used, with rare target, rare nontarget, and frequent standard stimuli delivered under identical conditions except that instructions to subjects described the targets to which subjects should respond but did not describe the nontargets. In Experiment 1, stimuli varied among modalities; in Experiment 2, auditory stimuli were employed. Both ERPs and HR were consistent with automatic processing preceding two stages of controlled processing. Rare stimuli evoked larger parietal P300 and initial HR deceleration than standards. Presumably because of load-reducing effects of long interstimulus intervals, targets and nontargets were not distinguished before a late slow wave and a late phase of HR acceleration. Neither rare stimulus elicited a recognizable frontal P3a.     

P300, handedness, and corpus callosal size: gender, modality, and task

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female subjects (n = 20/group), with auditory and visual stimulus modalities from single-stimulus and oddball tasks. P300 amplitude was larger across all conditions for left- compared to right-handed subjects at anterior and central electrode sites. P300 latency was shorter across all conditions for left- compared to right-handers. Task type did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males compared to females. When considered in the context of previously reported corpus callosal size differences for left- vs. right-handed and male vs. female participants, the findings suggest that the P300 reflects callosal size and inter-hemispheric transmission efficacy.     

Effects of the GABA mimetic drug, sodium valproate, on event-related potentials and its relation to the law of initial value

The effects of gamma-aminobutyric acid (GABA) mimetic drug sodium valproate (VPA) on event-related potentials (ERPs) were investigated in 18 healthy volunteers during an auditory odd ball task. VPA (200 or 400 mg) or an inactive placebo was administered according to a completely randomized double-blind, cross-over design. ERPs were recorded one hour after medication was given. VPA did not affect the latencies of N100, P200, N200 and P300. Although on the whole VPA had no effect on the amplitudes of the ERP components in the subjects, it increased the P300 amplitude in the low P300 amplitude subjects and decreased it in the high P300 amplitude subjects. This tendency toward a bidirectional response was also seen in the P200 and N200 amplitudes. It was concluded that the response which takes place being dependent on the difference in the initial values was recognized on the effect of a single administration of 200 or 400 mg VPA to ERPs. The results of this study are discussed, especially in relation to the law of initial value.     

Externalizing psychopathology and gain–loss feedback in a simulated gambling task: Dissociable components of brain response revealed by time-frequency analysis.

Externalizing is a broad construct that reflects propensity toward a variety of impulse control problems, including antisocial personality disorder and substance use disorders. Two event-related potential responses known to be reduced among individuals high in externalizing proneness are the P300, which reflects postperceptual processing of a stimulus, and the error-related negativity (ERN), which indexes performance monitoring based on endogenous representations. In the current study, the authors used a simulated gambling task to examine the relation between externalizing proneness and the feedback-related negativity (FRN), a brain response that indexes performance monitoring related to exogenous cues, which is thought to be highly related to the ERN. Time-frequency (TF) analysis was used to disentangle the FRN from the accompanying P300 response to feedback cues by parsing the overall feedback-locked potential into distinctive theta (4–7 Hz) and delta (     

Pain-related cerebral potentials in response to acute painful electrical stimulation in sheep

OBJECTIVE: To examine associations between late event-related cerebral potential amplitudes and behavioural responses to noxious electrical stimulation as an indicator of acute pain in sheep. DESIGN: Analysis of variance for the effects of stimulus intensity on the behaviour and event-related cerebral potential variables. PROCEDURE: Ninety-six brief constant current electrical pulse trains were presented to the front left leg of eight sheep at four intensities (2.5 to 10 mA) in a randomised order. An event-related cerebral potential and a graded flinch response were recorded for each stimulus and the 24 event-related cerebral potentials at each intensity were averaged to produce a mean waveform. Various components of this waveform were analysed and changes in these measures and the sheep's flinch response, as stimulus intensity increased, were determined. RESULTS: Both the flinch response and some event-related cerebral potential components, that is, peak amplitudes 114 [N1], 187 [P1], 318 [P2] and 230 [Pm] ms after stimulus onset, were significantly affected as stimulus intensity increased. CONCLUSION: These corresponding behavioural and event-related cerebral potential changes indicate the usefulness of using changes in the event-related cerebral potential to measure acute pain in sheep.     

High-density recording and topographic analysis of the auditory oddball event-related potential in patients with schizophrenia

BACKGROUND: Prior research has shown reductions of the N1, N2, and P300 auditory event-related potential (ERP) components in schizophrenic patients. Most studies have shown a greater P300 reduction in left versus right temporal leads in schizophrenic patients. These studies were done with sparse electrode arrays, covering restricted areas of the head, thus providing an incomplete representation of the topographic field distribution. METHODS: We used a 64-channel montage to acquire auditory oddball ERPs from 24 schizophrenic patients and 24 controls subjects. The N1, P2, N2, P300, and N2 difference (N2d) amplitudes and latencies were tested for group and laterality differences. Component topographies were mapped onto a three-dimensional head model to display the group differences. RESULTS: The schizophrenic group showed reduction of the N1 component, perhaps reflecting reduced arousal or vigilance, but no N1 topographic difference. An N2d was not apparent in the schizophrenic patients, perhaps reflecting severe disruption in neural systems of stimulus categorization. In the patients, the P300 was smaller over the left temporal lobe sites than the right. CONCLUSIONS: The increased ERP spatial sampling allowed a more complete representation of the dipolar nature of the P300, which showed field contours consistent with neural sources in the posterior superior temporal plane.     

Effects of prenatal exposure to PCBs on the neurological function of children: a neuropsychological and neurophysiological study

To determine the long-term neurotoxicity of prenatal exposure to polychlorinated biphenyls (PCBs), 54 children--27 'Yu-Cheng' ('oil disease') children and 27 controls--were administered a battery of tests, including the WISC-R, auditory event-related potentials (P300), pattern visual evoked potentials (P-VEPs) and somatosensory evoked potentials (SSEPs). Full-scale IQ scores on the WISC-R were lower for the Yu-Cheng group than for the control group. Mean P300 latencies were significantly longer, and P300 amplitude significantly more reduced, in the Yu-Cheng group than in the control group at Cz and Pz. There were no significant difference in peak latencies and amplitudes between the two groups for P-VEPs and SSEPs. These findings suggest that prenatal exposure to PCBs tends to affect high cortical function rather than the sensory pathway in the developing brain.     

Olfactory and auditory event-related potentials in Huntington's disease.

The influence of Huntington's disease (HD) on the olfactory event-related potential (OERP), an electrophysiological measure of olfactory information processing, has not been reported to date. In the present study, olfactory and auditory event-related potentials (ERPs) were recorded monopolarly from Fz, Cz, and Pz electrode sites in 8 patients with HD and 8 age- and gender-matched control participants. Results demonstrated that individuals with HD were delayed compared with controls on the P3 component of the OERP (p     

Effects of ethanol on temporal recovery of auditory-evoked potentials in individuals at risk for alcoholism

The present investigation examined the effects of placebo (P), low dose (LD), and high dose (HD) ethanol on auditory event-related potential (AEP) recovery functions in a group of males at high risk to develop alcoholism (HR; n = 23, mean = 22.3 years) and a low risk (LR; n = 27, mean = 23.0 years) control group. Condition order was randomized, with one condition (P, LD, or HD) per day and a minimum 1-day interval between conditions. For each subject, both blood alcohol levels (BALs) measured via breathalyzer, and event-related potentials recorded with the entire 10/20 International System, were assessed prior to and at mean intervals of 20, 60, 90, and 130 min after P, LD, or HD administration. A series of binaural auditory stimuli with randomly interposed interstimulus intervals of 0.5, 1.0, and 10.0 sec were used to elicit the N100 and P200 components of the AEP. Between-groups comparisons indicated that ethanol elicited risk group differences in recovery functions not present at baseline. The differences were manifested in the HR group as larger decrements in P200 amplitude during the ascending blood alcohol curve (acute sensitivity) and more rapid returns of both N100 and P200 to baseline levels during the descending blood alcohol curve (acute tolerance). These findings support Newlin and Thomson's (1990) Differentiator Model, suggesting that LR and HR individuals are differentially sensitive to the effects of ethanol.     

Differential associations of P300 amplitude and latency with cognitive and psychiatric function in solvent-exposed adults

Cognitive and mood changes are central components of solvent encephalopathy. This study examined event-related potentials in relation to neuropsychological and psychiatric function in solvent-exposed adults. Results revealed that longer P300 latency was associated with poorer cognitive test scores, whereas reduced P300 amplitude was related to increased psychiatric symptomatology. The findings suggest that the cognitive deficits and the psychiatric disturbance following solvent exposure may have different neurophysiological bases.     

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Reliability of event-related P3 parameters. Various parameters of the P3 wave were tested for reliability and test-retest stability. To this end, event-related P3 waves were evoked in 21 subjects during visual and auditory oddball tasks. The protocol was repeated one to two weeks later. Amplitude, latency and area between P3 and baseline were estimated by different procedures. The stability within and between sessions was assessed with the split-half method and a measure of test-retest reliability, respectively. A literature review revealed that latency estimation is most commonly done by computer-aided peak measurement, but determining peak parameters visually after interpellating superimposed artifacts turned out to be significantly more reliable. Interrater reliability for this visual inspection was very high if preestablished rules were employed. Amplitude and area were measured reliably by both computer-aided procedures and visual inspection. The area was quite stable both within and between sessions. Area can serve as a measure of cerebral activation and should therefore be determined. Based on the results recommendations are made about analyzing components of event-related potentials. The need to control for error variance is emphasized. This is the only way to improve methods enough that they will be suitable for use in single case diagnosis.     

ERPs in schizophrenia: effects of antipsychotic medication

Thirty unmedicated schizophrenics were compared to 29 age-matched controls on auditory and visual event-related brain potential (ERP) paradigms. Twenty-one of these patients were tested again after 1 week on placebo and after 4 weeks on antipsychotic medication. Before treatment, N1, N2, and P3 components of the auditory ERP were smaller in the schizophrenics than in the controls. Although visual N2 was smaller in schizophrenics, visual P3 was not. In spite of significant clinical improvement with antipsychotic treatment, amplitudes of auditory and visual N1, N2, and P3 were not significantly changed. Higher blood levels of antipsychotic medication were related to reductions in auditory P3 latency, however. In addition, higher levels of cerebrospinal fluid (CSF) MHPG (methoxyhydroxyphenylglycol) were associated with larger auditory N1s and larger auditory and visual P3s, suggesting an influence of arousal on these components in schizophrenics. In spite of this influence, reduction of the auditory P3 in schizophrenia is an enduring trait of the disease, which is not affected by antipsychotic medication or clinical improvement.     

P300 latency: abnormal in sleep apnea with somnolence and idiopathic hypersomnia, but normal in narcolepsy

To evaluate cognitive abnormalities in excessive daytime sleepiness (EDS) using cognitive evoked potentials (P300), and to evaluate if P300 measures differentiate among disorders of EDS, a series of EDS subjects were administered a polysomnogram, auditory and visual P300 testing using 31 scalp electrodes, and a multiple sleep latency test. P300 variables were compared with those of normal subjects. Forty normal subjects ages 16 to 65 years, and 69 EDS patients ages 16 to 65 years were used. Of these, 39 had profound obstructive sleep apnea (OSA, Respiratory Disturbance Index or RDI > 80/h sleep) with severe somnolence (Mean Sleep Latency < 5 min). Twenty-two had idiopathic hypersomnia (IH). Eight had narcolepsy. The normals and the three EDS groups did not differ in age. IH and profound OSA patients had longer visual P300 latency than normals or narcolepsy patients (p < 0.05). (p < 0.05). IH and profound OSA patients had longer auditory P300 latency than normals. They had smaller auditory P300 amplitude than narcolepsy patients. There were visual P300 latency topographic differences between normals and profound OSA patients. In conclusion, IH and profound OSA patients show cognitive evoked potential evidence of cognitive dysfunction. Narcolepsy patients do not show such evidence. Visual P300 latency differentiates among disorders of EDS.     

The effect of stimulus sequence on the waveform of the cortical event-related potential

The waveform of the cortical event-related potential is extremely sensitive to variations in the sequence of stimuli preceding the eliciting event. The waveform changes were manifested primarily in the amplitudes of the negative component of the potential that peaked at 200 milliseconds, the positive component that peaked at 300 milliseconds, and the slow-wave components. A quantitative model was developed relating the waveform changes to changes in event expectancy. Expectancy is assumed to depend on a decaying memory for events within the prior sequence, the specific structure of the sequence, and the global probability of event occurrence. For stimuli relevant to the task, the less expected the stimulus the larger the amplitudes of late components of the event-related potentials.     

Extended transsternal thymectomy

We recorded auditory event-related potential (ERP) by using the standard oddball paradigm in seven amnestic patients. Patients were divided into three groups according to brain CT or MRI findings. (1) Three patients with no detectable lesion, including two patients studied during the episode of transient global amnesia, showed a well-defined P300. (2) Three patients with detectable lesions in the mesial temporal lobes did not show any wave form corresponding to P300. In two of these three patients, the ERP wave form showed a significant change in accordance with the improvement of MRI findings. (3) One patient who had a hypothalamic lesion due to total resection of craniopharyngioma showed a low-amplitude P300. Although neuropsychological examinations showed selective and severe impairment of recent memory function in all of these patients, no significant relationship was found between the degree of memory disturbance and P300 abnormality. These results suggest that P300 is more affected by existence and extension of brain lesions, especially in the mesial temporal lobes, rather than degree of memory disturbance. However, these results do not necessarily suggest that the potential generated in the mesial temporal lobes is directly recorded as a component of the scalp-recorded P300.     

The relation between electric auditory brain stem and cognitive responses and speech perception in cochlear implant users

Electrically evoked brainstem responses (EABR) and event-related cortical potentials were recorded in seven postlingually deaf adults who were experienced users of a Nucleus multichannel cochlear implant. The patients were divided into two subgroups: good performers and moderate performers. Poor EABR were found in two of the moderate performers. The latencies and amplitudes of the cortical N1 P2 complex in the good performers were within the same range as those of subjects with normal hearing, but were deviant in the group of moderate performers. This may indicate disturbed cochleotopical organization of the auditory cortex in the latter group. P300 measurements in the good performers showed normal latencies, whereas in the moderate performers they were prolonged. The results suggest that the outcomes of electrophysiological measurements to assess the integrity of a patient's auditory neural system on a brainstem and a cortical level, are related to the patient's performance with the cochlear implant.