Event-related potential assessment of information processing after closed head injury

We evaluated alterations in information processing after closed head injury as a function of task demands and stimulus modality. Visual and auditory discrimination tasks were administered to 11 survivors of a head injury and 16 matched healthy controls. In auditory tasks, compared with controls, the survivors had smaller N100s, smaller and later N200s, a more posterior scalp distribution of N200, and longer P300 and response latencies. Auditory N200 and P300 correlated highly with duration of unconsciousness. In contrast, in visual tasks, only a reduced N200 in the survivors differentiated the groups. Our results indicate that processing of auditory stimuli, including the perception and discrimination of stimulus features and the evaluation and categorization of stimuli, may be impaired after head trauma. Visual sensory processing may be spared, but higher-order visual processing involved in stimulus classification may be compromised.     

Modification of sudden onset auditory ERP by involuntary attention to visual stimuli.

To investigate the cross-modal nature of the exogenous attention system, we studied how involuntary attention in the visual modality affects ERPs elicited by sudden onset of events in the auditory modality. Relatively loud auditory white noise bursts were presented to subjects with random and long inter-trial intervals. The noise bursts were either presented alone, or paired with a visual stimulus with a visual to auditory onset asynchrony of 120 ms. In a third condition, the visual stimuli were shown alone. All three conditions, auditory alone, visual alone, and paired visual/auditory, were randomly inter-mixed and presented with equal probabilities. Subjects were instructed to fixate on a point in front of them without task instructions concerning either the auditory or visual stimuli. ERPs were recorded from 28 scalp sites throughout every experimental session. Compared to ERPs in the auditory alone condition, pairing the auditory noise bursts with the visual stimulus reduced the amplitude of the auditory N100 component at Cz by 40% and the auditory P200/P300 component at Cz by 25%. No significant topographical change was observed in the scalp distributions of the N100 and P200/P300. Our results suggest that involuntary attention to visual stimuli suppresses early sensory (N100) as well as late cognitive (P200/P300) processing of sudden auditory events. The activation of the exogenous attention system by sudden auditory onset can be modified by involuntary visual attention in a cross-model, passive prepulse inhibition paradigm.     

Stimulus modality and Go/NoGo effects on P3 during parallel visual and auditory continuous performance tasks

Task and modality effects on P3 latency, amplitude, and scalp topography were studied during parallel versions of visual (VCPT) and auditory (ACPT) continuous performance tasks using a Go/NoGo paradigm (A-X CPT). Both the ACPT and VCPT incorporated five conditions including Go and NoGo stimulus sequences as well as three other nontarget conditions. The goal was to evaluate the functional significance and modality specificity of the P300 response and the NoGo P3. Analyses were performed using both raw and normalized data to make comparisons across modalities. For both modalities, the Target X (Go) and three nontarget conditions elicited maximum P3 amplitudes over the posterior scalp sites and qualified as classical P300 responses. The NoGo condition was associated with an increase in central-frontal amplitude compared to the Target X condition. The scalp topography of the P300/P3 for Go and NoGo conditions, as well as all other conditions, was the same for both modalities, supporting the modality independent nature of both P300 and the NoGo P3. Min-Max normalization of P3 amplitudes did not change the condition-topography relationships.     

Auditory and Visual P300s in Temporal Lobectomy Patients: Evidence for Modality-Dependent Generators

The P300 component of the event-related brain potential (ERP) was studied in epileptic patients with unilateral resections of medial temporal lobe areas of the brain. The patients and controls were tested in an oddball paradigm in two conditions: counting and reaction time. Both auditory and visual stimuli were used to elicit ERP activity in different blocks. Despite the reported presence of locally-generated auditory and visual P300-like potentials in these areas, no evidence was found of any surgically-related hemispheric asymmetries in the scalp distribution of the P300 or Slow Wave for stimuli in either modality. Moreover, compared to normal controls, there were no significant reductions in overall P300 amplitude in the patients. The patients did show a double dissociation in their frontal ERP activity: the left temporal lobectomy patients showed apparent decreased frontal auditory P300 amplitudes but normal visual P300 amplitudes, whereas the right temporal lobectomy patients showed the opposite pattern. These results appeared to be due to the presence of a long-duration slow wave rather than to alterations in P300 amplitude. These data do not support the presence of a significant contribution by a hippocampal/amygdala generator to the activity of the scalp-recorded P300 in the oddball paradigm. Topographic comparisons on normalized amplitudes revealed significantly different scalp distributions as a function of stimulus modality, event probability, and task for both the P300 and Slow Wave components. These data indicate that the amplitude variations associated with each experimental variable are due to the activity of a separate underlying neural source. The sources of task and probability effects on P300 and Slow Wave amplitude each appeared to be modality-independent generators. The nature of the third, modality-related generator is less clear. These results uphold the tenets of the model of P300 amplitude proposed by Johnson (1986) and argue against the idea that the P300 is a unitary phenomenon.     

Auditory p300 event-related potentials in fibromyalgia patients

This study assessed the cognitive brain function measured by the cognitive P300 auditory event-related potentials (ERPs) in female fibromyalgia (FM) patients and compared the results with those from healthy age and education-matched controls. The relationship of the P300 potentials to the pain threshold of patients was also investigated. The P300 component of the auditory ERPs were studied in 11 female FM patients and 10 age and education-matched healthy controls. None of the patients were taking antidepressants such as amitriptyline or serotonin-reuptake inhibitors. The P300 latencies of the patients were not significantly different whereas the N2P3 amplitudes were significantly lower than the controls. The P300 latencies in the patients negatively correlated with the total myalgic scores (TMS) (r= -0.73) and the control point scores (CPS) (r=-0.85). On the other hand, the P300 amplitudes showed a significant correlation with the TMS (r=0.61) and the CPS (r=0.60). There was no significant correlation between the anxiety and depression scores with the P300 latency or amplitudes. These results showed cognitive impairment, which was mainly expressed by the lower N2P3 amplitudes in patients with FM, and its clinical relevance requires further research.     

Auditory event-related potentials (ERPs) in healthy subjects and patients with dementia

To study the effects of aging and gender differences of ERP components, auditory ERPs were recorded in 106 healthy subjects. Forty-three patients with dementia of the Alzheimer type and 24 patients with vascular dementia were also studied. In healthy subjects, there was a significant positive linear correlation between P300 latency and age, with P300 latency increasing at the rate of 1.5 msec/year. Neither N100 nor P200 component was correlated with age. The amplitudes of N100, P200 and P300 components in females were slightly larger than those in males, but the differences were not significant. Not only P300 latencies but also P200 latencies were significantly different in healthy subjects, patients with dementia of the Alzheimer type and those with vascular dementia. In 74.4% of patients with dementia of the Alzheimer type and 62.5% of those with vascular dementia, the P300 latency was over 2 SE above the age-estimated regression line. The difference of the P300 latency prolongation may have resulted from the severity of dementia but not from the etiology of dementia.     

Closed head injury-related information processing deficits: an event-related potential analysis.

Event-related potentials (ERPs) can elucidate aspects of sensory and cognitive processing that have been compromised due to closed head injury. We present the results of two investigations, one previously unreported, in which we used ERPs to evaluate information processing in head-injury survivors. In the first study, we used visual and auditory reaction time tasks differing in attentional demands to assess processing after head trauma. We found numerous changes in auditory processing in survivors: longer reaction times (but normal accuracy), longer N200 and P300 latencies, and reduced N100 and N200 amplitudes. In contrast, on visual tasks, only reduced N200 amplitude distinguished survivors and controls. To increase attentional demands, in a second study, we administered the continuous performance test (CPT). Survivors performed with lower accuracy than controls on visual and auditory tasks, and their ERPs were characterized by smaller visual and auditory N200s and P300s and smaller auditory N100s. We also present a synthesis, derived from a review of the literature, of closed head-injury effects on ERPs. Our own findings are in agreement with that synthesis. Namely, cognitive ERP components are more sensitive than sensory components to the effects of trauma. Specifically, in survivors, the amplitudes of N200 and P300 are often reduced, and their latencies prolonged. In general, as compared with visual ERPs, auditory ERPs may be more susceptible to the effects of closed head injury, suggesting that the auditory processing system is more vulnerable than the visual system. We conclude by discussing the potential use of ERPs to monitor clinical course and recovery in survivors of closed head injury.     

Heritability of event-related brain potentials in families with a history of alcoholism.

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism.     

Effects of aerobic exercise and gender on visual and auditory P300, reaction time, and accuracy

Visual and auditory reaction times (RTs) have been reported to decrease during moderate aerobic exercise, and this has been interpreted as reflecting an exercise-induced activation (EIA) of cognitive information processing. In the present study we examined changes in several independent measures of information processing (RT, accuracy, P300 latency and amplitude) during exercise, and their relationship to visual or auditory modalities and to gender. P300 latencies offer independent measures of cognitive speed that are unrelated to motor output, and P300 amplitudes have been used as measures of attentional allocation. Twenty-four healthy college students [mean (SD) age 20 (2) years] performed auditory and visual “oddball” tasks during resting baseline, aerobic exercise, and recovery periods. Consistent with previous studies, both visual and auditory RTs during exercise were significantly shortened compared to control and recovery periods (which did not differ from each other). We now report that, paralleling the RT changes, auditory and visual P300 latencies decreased during exercise, indicating the occurrence of faster cognitive information processing in both sensory modalities. However, both auditory and visual P300 amplitudes decreased during exercise, suggesting diminished attentional resource allocation. In addition, error rates increased during exercise. Taken together, these results suggest that the enhancement of cognitive information processing speed during moderate aerobic exercise, although operating across genders and sensory modalities, is not a global facilitation of cognition, but is accompanied by decreased attention and increased errors.     

Effects of aging on event-related brain potentials and reaction times in an auditory oddball task

Auditory event-related potentials (ERPs) were recorded from 71 healthy individuals between 18 and 82 years of age during performance of a disjunctive reaction time task in an auditory oddball paradigm. The effects of aging on reaction times and on the latencies, amplitudes, and distributions of each of the main ERP components were examined. No significant slowing of the reaction times of the elderly subjects was observed in relation to the younger ones. The peak latencies of both the N1 and P2 components elicited by standard tones were slightly but significantly slowed with age. In the ERPs of target tones, the later, endogenous components (N2, P3, and SW) showed linear increases in latency as a function of age; the later the component, the longer the age-related delay. In general, aging was associated with less negativity (both N2 and SW) and more positivity (P3) over the anterior scalp, together with a smaller P3 and a more pronounced N2 over posterior scalp areas. Most of the effects observed in target ERPs were also evident in the difference waves derived from subtraction of the standard from the target ERPs, although the slope of the age-related latency increase of N2 was shallower and that of the P3 was steeper in the difference ERPs. These findings are discussed in relation to previous accounts of ERP changes with aging.     

Heritability of event-related brain potentials in families with a history of alcoholism

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:383–390, 1999. © 1999 Wiley-Liss, Inc.     

An event-related potential study on the impairment of automatic processing of auditory input in schizophrenia

Summary Mismatch negativity (MMN) and P300 to auditory stimuli was carried out using global field power (GFP) in 25 schizophrenics and 25 normal controls. The peak latencies of MMN and P300 were significantly longer in schizophrenics than in normal controls, and the differences in MMN were marked in the frontal regions. The peak amplitudes of MMN and P300 were significantly smaller in schizophrenics. The scalp distribution of MMN to 1050 Hz tone differed between the two groups, although that to 1100 Hz was similar to each other. The results indicate an impairment in the automatic discrimination process of auditory input in schizophrenics.     

Evaluation of auditory, visual and olfactory event-related potentials for comparing interspersed- and single-stimulus paradigms

Background

An interspersed-stimulus paradigm (ISP) for event-related potential (ERP) recordings in which different sensory modality stimuli are presented within the same test session was developed to minimize recording time and facilitate modality comparison. The present study compared the ISP with a single-stimulus paradigm (SSP), using auditory, visual, and olfactory stimuli.

Method

Normal participants (n = 16) were assessed on two independent test occasions to obtain data on inter-paradigm and test-retest reliability. Peak amplitude/latency and area measures were obtained for the N1, P2 and P3 peaks for each paradigm.

Results

Except for larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP, no significant differences in amplitudes or latencies were found between the two paradigms. Correlation coefficients between paradigms were generally fairly high (amplitude mean r = 0.76; latency r = 0.42). Test-retest reliability within paradigms for amplitudes (ISP r = 0.70; SSP r = 0.68) and latencies (ISP r = 0.44; SSP r = 0.42) was similar across paradigms.

Conclusion

The findings suggest that the ISP, compared to the SSP, produces, in general, highly comparable auditory, visual, and olfactory peak amplitudes and latencies, and comparable reliability estimates, even though the ISP takes much less time to record (25 vs. 50 min). The larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP may be attributable to a less predictable stimulus environment. Thus, this method enables systematic comparisons of ERP peaks across sensory modalities while reducing testing time. Practical implications are discussed.     

P300 Development from Auditory Stimuli

Event-related potentials (ERPs) were elicited with an auditory discrimination paradigm in 20 adult subjects. The amplitude and latency of the N1, P2, N2, and P3 (P300) components were measured from each two-trial average and successively after each two-trial block were added to the ERP average. The dual trial-to-trial analysis generally demonstrated consistent component amplitudes and latencies across trials. The successive average analysis found that component amplitudes decreased significantly while their latencies remained relatively constant as additional trials were incorporated into the average. The results suggest that ERP component latencies are stable, while amplitudes decrease with increased numbers of trials. The implications for the application of P3 in the assessment of individual differences are discussed.     

Olfactory, auditory, and visual ERPs from single trials: no evidence for habituation.

Event-related potentials (ERPs) using olfactory, auditory, and visual stimuli were recorded from young adults to assess possible component habituation across single trials among modalities. A single-stimulus ERP paradigm was used that employed a 10-min inter-stimulus interval (ISI) to minimize possible sensory adaptation and three stimulus trials for each modality to assess initial habituation effects. The present findings were: (1) P3 amplitude does not habituate appreciably over the initial three trials but may increase from the first to second trial. (2) ERPs from a single-stimulus paradigm with a very long ISI produce significantly correlated component amplitudes for the olfactory, auditory, and visual modalities. (3) P3 amplitude from olfactory stimuli demonstrated scalp topography similar to that for auditory and visual ERPs. These findings suggest that the single-stimulus task using a long ISI produces highly comparable and stable P3 components from olfactory, auditory, and visual stimuli. Application of single-stimulus paradigm to olfactory ERP methods is supported.     

Event-related potentials to auditory and visual selective attention in schizophrenia.

BACKGROUND: Prior studies have shown a consistent reduction of the auditory P300 in schizophrenia, while the visual attention findings have been mixed. Both the auditory and visual N2b, an earlier, modality-specific attention index, are reduced in schizophrenia, sometimes despite sparing of the visual P300. Thus there may be a dissociation between the N2b and P300 attention effects in auditory and visual modalities in schizophrenia. METHODS: Thirteen patients and thirteen controls observed symbols appearing on a screen, paired with simultaneous tones. In some blocks subjects responded to one of the symbols, in others to one of the tones. The N2b was predicted to be reduced in the patient group in both auditory and visual attention but the P300 reduced only while attending to tones. RESULTS: Results showed a reduction of the N1 component in the patient group in the auditory condition but not in the visual. There was a reduction of the N2b target-minus-non-target difference wave in the patients in both auditory and visual target conditions. The P300 component was larger overall in the control group in both modalities, but did not show the usual enhancement to auditory targets in the control group. CONCLUSIONS: These findings suggest that the ability to selectively attend to a target in one modality while ignoring the other is compromised in patients with schizophrenia. Perceptual processing appears to be impacted in the auditory modality while remaining intact in the visual. The N2b appears more vulnerable than the P300 in both auditory and visual attention in schizophrenia.     

老年慢性精神分裂症患者的听觉P300初步研究

应用丹表仪器，完成３４例患者和４０例正常老人的Ｐ３００检测。结果表明与正常老人比较，患者组靶潜伏期主成分（Ｎ１－Ｐ２－Ｎ２－Ｐ３）前移（Ｐ＜０．０１），靶波幅Ｐ２和Ｐ３降低（Ｐ＜０．０１）。非靶改变同靶刺激。提示老年慢性精神分裂症患者的听觉Ｐ３００仍有待进一步研究。     

P300: The Similarities and Differences in the Scalp Distribution of Visual and Auditory Modality

To examine the topographic relationship of P3(00) between the visual and auditory modalities, especially to examine whether there are any modality-specific hemispheric differences of P3 in normal adults. Methods: The P3s were recorded from the same 41 normal right-handed males between the ages of 20 and 33 in both a typical auditory oddball task and a visual oddball paradigm with novel stimuli, with an extensive set of 61 scalp electrodes. In addition to the visual comparison and quantitative assessment of current source density (CSD) maps between the two modalities, canonical correlation analyses on the P3 raw amplitudes and examination of interaction effects of modality × location on both raw and normalized P3 data were performed. Results: The canonical correlation between modalities was generally high, especially at the left parietal brain region. There were no significant hemispheric effects in anterior brain but significant left-greater- than-right hemispheric effects in posterior brain regions in both modalities; modality-specific hemispheric effect was observed only at the parietal region. Strong surface current density activities were observed in the midline parietal-occipital area, and left and right boundary areas of temporal and inferior frontal region. Conclusions: The topographic similarities between P3s recorded in the visual and auditory modality outnumber the differences. Combining data from CSD assessments and profile analysis of P3 topography support the hypothesis of multiple generators of P3 that are differentially active in processing stimuli from different sensory modalities and are not symmetrically distributed between the two hemispheres.     

老年慢性精神分裂症患者事件相关电位P300改变的意义

目的观察老年慢性精神分裂症(SCS)患者P300的变化.方法共有40例正常老人和34例SCS患者,应用丹麦仪器及两种短音刺激,完成P300检查.结果部分SCS患者波形有切迹.Fz、Cz和Pz三记录点比较无差异.N1靶潜伏期在额区右侧延长于左侧.与正常老人比较, SCS患者靶潜伏期主成分(N1-P2-N2-P3)前移(P＜0.01),靶波幅P2和P3降低(P＜0.01).非靶改变同靶刺激.结论P300可以辅助评定SCS患者的认知功能状态.     

Time course of the unmasked attentional blink

The Attentional Blink (AB) usually refers to the impaired report of a second target (T2) if it appears within 200–500 ms after a first target within a rapid sequence of distractors. The present study focused on a less studied AB variant known as the unmasked AB, where T2 is the last item of the sequence and T2 report is unaffected. This aspect of the unmasked AB holds promise for an experimental paradigm in which measures of on‐going event‐related processing are unconfounded by differences in late‐stage processing. To fully characterize the unmasked AB paradigm, we used a randomization statistics approach to comprehensively examine the electroencephalographic signature of the unmasked AB. We examined the unmasked AB with auditory and visual T2s—participants attended to either the auditory or visual information within a sequence of paired auditory‐visual stimuli, and reported targets within the attended modality stream while ignoring the other. As predicted, T2 report was unaffected by the unmasked AB. The visual AB was associated with delayed but intact N2 and P3 components, and a suppressed N1. We suggest that this N1 is linked to auditory processing of the distractor stream, and reflects the cognitive system prioritizing the processing of visual targets over auditory distractors in response to AB‐related processing load. The auditory AB only indicated a delayed but intact P3. Collectively, these findings support the view that the AB limits the entry of information into consciousness via a late‐stage modal bottleneck, and suggest an ongoing compensatory response at early latencies.