Button-pressing affects P300 amplitude and scalp topography.

BACKGROUND: Scant and equivocal research exists examining the effects of button-pressing on P300. Button-pressing may decrease P300 latency and amplitude. The melding of motor potentials and P300 may also confound studies of P300 topography, such as studies of temporal scalp-area asymmetries in schizophrenia. METHOD: P300 was measured on button-press and silent-count tasks in control subjects. An estimate of motor activity was constructed from a simple reaction time task, with reaction times matched to the button-press task. The motor estimate was subtracted from the button-press P300 to assess Kok's (1988) additive model. Lastly, lateral P300 from schizophrenia patients was compared with each condition's P300. RESULTS: P300 was smaller and its topography different in the button-pressing task relative to silent-counting. The motor-correction procedure generated a P300 with normal topography. Comparison of the button-press P300 in controls to the silent-count P300 in schizophrenia patients reduced a significant lateral asymmetry to trend level. This asymmetry was significant after the correction procedure. CONCLUSIONS: Button-pressing generates smaller P300 than silent-counting. Also, P300 topography in button-pressing tasks is confounded by motor potentials. The distortion can be corrected with a motor potential estimate. Motor potentials can occlude differences in P300 topography between groups.     

精神分裂症患者听觉P300颅脑空间分布的初步研究

目的探讨精神分裂症患者认知电位的脑区域性改变特征。方法应用Ｐ３００地形图的方法，对２４例偏执型精神分裂症患者与５０名正常人进行对比研究。结果患者组内源成分Ｎ２、Ｐ３波幅值在左半球额区、颞区及中央区低于正常人（Ｐ＜０．０５）；外源成分Ｎ１、Ｐ２波幅值高于正常人（Ｐ＜０．０５）。结论提示精神分裂症患者认知电位异常存在着偏侧性和区域性，支持精神分裂症大脑左半球机能障碍的学说。外源成分的改变将有助于精神分裂症的分型诊断     

Influences of age and pubertal development on P300 amplitude trajectory across two years in female adolescents

The P300 event-related potential (ERP) has been extensively studied across the human lifespan. However, many studies examining age-related effects are cross-sectional, and few have considered the unique role that pubertal development may have on P300 developmental trajectories. The current study examined whether age, pubertal maturation or their interaction predicted changes in P300 amplitude over two years among 129 females between the ages of 8 and 15 years at baseline. Participants completed a flanker task while EEG was recorded at a baseline and two-year follow-up visit. Both baseline age and increased pubertal development were associated with smaller P300 amplitude at follow-up. However, the influence of age was qualified by an interaction between age and pubertal maturation: among younger girls only, increased pubertal development predicted decreases in P300, whereas decreased pubertal development predicted increases in P300. These data indicate that pubertal timing impacts neurodevelopmental changes in P300 amplitude – such that high versus low pubertal development among 8- to 10-year-old girls predicted differential trajectories of neural activity. In light of links between reduced P300 and mental health disorders, such as depression, future studies might examine whether neurodevelopmental changes influenced by early-onset pubertal development could account for increases in these mental health problems.     

Changes in P3 waves with event repetition: long-term effects on scalp distribution and amplitude.

Event-related brain potentials to tachistoscopically presented events were recorded from adults 24--36 years of age. Subjects counted the number of target events (P = 0.12) randomly interposed in sequences of background events (either P = 0.88 or P = 0.76). In some sequences, slides bearing the letter A were targets and those bearing the letter B were backgrounds; the reverse was true in the other sequences. Also interposed (P = 0.12) in these sequences of targets and backgrounds were one of two types of non-target events: in some sequences non-targets were slides (termed dims) bearing any one of the letters C to Z and having one-tenth the luminance of the target and background slides, while in the others, they were slides bearing 'novel' patterns, each consisting of a different, quasi-random, unrecognizable color pattern. The scalp amplitude distribution of P3 waves to novels were initially frontal, but, with repeated presentations of novel events, they became parietal. The scalp distributions of P3 waves to targets and dims were both initially parietal and did not change with repeated presentations of target and dim events. P3 amplitudes to targets were unaffected by repeated presentations of target events. However, P3 amplitudes to dims and novels were affected. P3 amplitudes to dims decreased linearly at Fz, Cz and Pz with repetition of dims. P3 amplitudes to novels decreased at Fz and increased at Pz with repetition of novels. An abbreviated analysis of possible effects of sequential event probabilities on P3 amplitudes and latencies to novels, dims and targets was performed and no effects were found. It is suggested that P3 waves may be affected by at least 4 factors: the facility with which events may be categorized by subjects, the importance attached to events (via task instructions, subjective assessment of the contents of events, etc.), a priori category probability, and sequential event structure.     

P300 event-related potential amplitude and impulsivity in cocaine-dependent subjects

Previous studies report reduced amplitude of the P300 event-related potential in cocaine-dependent individuals. Cocaine dependence is also associated with increased impulsivity, possibly due to deficits in cognitive function that are associated with reduced P300 amplitude. In the current study, the relationship between cocaine dependence, impulsivity, and P300 amplitude were examined. An auditory oddball event-related potential task along with self-report (Barratt Impulsiveness Scale version 11) and behavioral laboratory (Immediate and Delayed Memory Task) measures of impulsivity were assessed in healthy controls (n = 14) and subjects who met DSM-IV criteria for current cocaine dependence (n = 17). P300 amplitude was reduced and self-reported and behavioral laboratory impulsivity scores were elevated among the cocaine-dependent group compared to controls. There was a positive correlation between the questionnaire and behavioral laboratory measures of impulsivity, and a negative correlation between impulsivity measures and P300 amplitude. The correlation between self-reported impulsivity scores and P300 amplitude remained after taking into account the number of childhood conduct disorder symptoms. This study supports the hypothesis that the basic neurophysiology responsible for the P300 amplitude in cocaine-dependent individuals is associated with impulsivity independent of a history of childhood conduct disorder symptoms.     

Reduced P300 and P600 amplitude in the hollow-mask illusion in patients with schizophrenia

Illusions provide a useful tool to study the mechanisms by which top-down and bottom-up processes interact in perception. Patients suffering from schizophrenia are not as subject to the hollow-mask illusion as healthy controls, since studies have shown that controls perceive a hollow mask as a normal face, while patients with schizophrenia do not. This insusceptibility to the illusion is indicating a weakened top-down processing in schizophrenia and little is understood about the neurobiology of this phenomenon. We used event-related potentials to investigate the hollow-mask illusion in patients with schizophrenia and healthy controls. We hypothesized that there would be a visible reduction of top-down processing in the patients' group and that this reduction would occur in the late stages of processing. We found significantly decreased amplitudes in the P300 and P600 components in the patients' group, indicating that visual information does not benefit from frontal, parietal or temporal activity for perceiving incoming stimuli. We propose that a deficit in functional connectivity may be responsible for impaired top-down visual processing in schizophrenia. These data further the understanding of the time course of top-down processing in patients with schizophrenia.     

The pattern flash elicited P300-complex (PF-P300): dynamics of its topographic scalp distribution in different states of visual attention

PF-P300 has been recorded from 13 healthy male subjects (21-35 years) in two different conditions of visual attention (transient versus sustained attention) at 16 electrode locations (10/20-system) against linked mastoids. The PFP300 complexes were measured and mapped. Thus, we obtained the following: (1) N250 did not show any significant differences between both conditions. (2) PF-P300, however, showed significantly different (p less than or equal to .05) maps between both conditions, especially bilateral frontal and left occipital with the measured PFP300a-amplitudes being higher (p less than or equal to .01) under sustained attention. The PFP300a-latencies did not show such differences. (3) N400 showed similar (p less than or equal to .001) differences in its mean peak distribution, but its latencies were shorter (p less than or equal to .01 resp. .0001) at all recording sites (except Fz, Pz) in condition (2). (4) Further evaluation of the PFP300-complex under sustained attention by means of increment mapping and multichannel potential measurements showed that PFP300 first rises at Fz, Pz, then spreads over the left occipital region and culminates bilateral frontal and parieto-occipital. Interestingly, the latencies of N250 and PFP300a were shorter at O1 (p less than or equal to .01) than at O2. With the help of electrical brain mapping it is possible to study the dynamics of both the PFP300 scalp distribution between two distinct mental states and within one mental state.     

Heartbeat perception and P300 amplitude in a visual oddball paradigm.

OBJECTIVE: The perception of bodily signals ("interoceptive awareness") was found to modulate evoked potential components, especially the P300, in response to emotional pictures and to internal signals. It remains an open question whether this variable is related to more elaborated information processing in general. METHODS: The present study investigated the relationship between heartbeat perception and the amplitude of the P300 to target stimuli in a visual oddball paradigm. RESULTS: Interoceptive awareness was positively correlated with the P300 amplitude at Cz which remained significant after controlling for anxiety differences. CONCLUSIONS: Our results demonstrate a positive relationship between interoceptive awareness and the attentive processing of visual stimuli. SIGNIFICANCE: Interoception is related to more elaborated information processing in general. This effect could be mediated by arousal differences and might rely on common neuroanatomical structures.     

P300 amplitude as a possible correlate of frontal degeneration in schizophrenia

The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 component of event-related electrical potentials (ERP) has been related to the different degree of damage to gray and white matter. This study explores the possible relationship between P300 amplitude and/or latency and the existence of degenerative processes in schizophrenia, by assessing its correlation with volume of sulcal CSF and duration of illness, as transversal indicators of neurodegeneration. Nineteen patients (14 males, 5 females) and 13 controls (6 males, 7 females) were studied with MRI and electrophysiological records (P300). The possible influence of sex and age at the time of the exploration was statistically controlled in both groups. The results show a significant negative correlation between P300 amplitude and prefrontal CSF volume in the patient group. A lower though still significant correlation was also found between P300 amplitude and duration of illness, whereas no correlation was found in the control group. These results support the hypothesis that P300 amplitude may be interpreted as a marker of neurodegeneration in schizophrenia.     

Lateralization of the epileptogenic focus in temporal lobe epilepsy by scalp P300

The P300 is a cognitive event-related potential partially generated by the amygdala/hippocampus complex, the most common source of temporal lobe epilepsy (TLE). In order to test the hypothesis that scalp P300 amplitude is reduced ipsilateral to the epileptogenic focus in TLE, we performed a prospective study of 15 subjects with TLE and compared the lateralizing ability of scalp P300 to interictal EEG. P300 asymmetries in TLE were compared with asymmetries in a control group. P300 amplitude was significantly attenuated ipsilateral to the epileptic focus. P300 amplitude reduction correctly lateralized the focus in 82% of the cases (p = 0.02). We conclude that scalp P300 accurately lateralizes the epileptogenic focus in TLE. Further studies are needed to define the potential role of P300 in the presurgical evaluation of TLE.     

The relation between asymmetry and amplitude of the P300 field in schizophrenia.

OBJECTIVES: A general reduction of auditory P300 amplitude is one of the most consistently replicated observations in schizophrenic patients. However, a left hemisphere amplitude reduction is discussed controversely. METHODS: Encouraged by this controversy we analysed P300 data of 53 controls and 60 patients of the schizophrenia spectrum (ICD-10: F20, F23, F25). RESULTS: Our main result was the finding of the correlation between general amplitude and hemispheric asymmetry in the patient group: low general amplitudes were assigned to a left hemispheric amplitude reduction, high amplitudes to a right hemispheric reduction. Based on this result, we grouped all subjects according to their hemispheric asymmetry pattern. The control group and the group of schizoaffective patients (F25) with a left hemispheric amplitude reduction showed the inverse asymmetry pattern of P300 amplitude compared to subjects with a right hemispheric amplitude reduction. In contrast, the schizophrenic patients (F20) showed only a difference in P300 amplitudes measured at electrode sites of the left hemisphere. Additionally, we could show, that the amount of the general amplitude reduction in patients was different between the diagnostic groups. CONCLUSIONS: We conclude that a left hemispheric amplitude reduction is not a general feature of schizophrenia but it seems to be pathological when combined with a general amplitude reduction.     

N200 latency and P300 amplitude in depressed mood post-traumatic brain injury patients

In order to examine the independent and combined effects of depressive symptoms and traumatic brain injury on event-related potential (ERP) components, we classified traumatic brain injury (TBI) patients as depressed and non-depressed mood according to their scores on the Zung Self-rating Depression Scale (SDS). Non-depressed mood post-traumatic brain injury patients (NondepTBI, n=9), depressed mood post-traumatic brain injury patients (DepTBI, n=26), and normal healthy control subjects (HC, n=10) were assessed for N100, N200, and P300 latencies and amplitudes by the auditory "oddball paradigm". DepTBI subjects had significantly prolonged N200 latency and low P300 amplitude compared with the NondepTBI and HC groups. A longer P300 latency in the NondepTBI and DepTBI than in the HC groups was found. A prolongation of N200 latency accompanied by low P300 amplitude may be a characteristic of post-traumatic brain injury patients with depressed mood. Prolonged P300 latency may be more closely associated with TBI than with depression, as it was significantly greater in both the DepTBI and NondepTBI, than in the HC group.     

N200 latency and P300 amplitude in depressed mood post-traumatic brain injury patients

In order to examine the independent and combined effects of depressive symptoms and traumatic brain injury on event-related potential (ERP) components, we classified traumatic brain injury (TBI) patients as depressed and non-depressed mood according to their scores on the Zung Self-rating Depression Scale (SDS). Non-depressed mood post-traumatic brain injury patients (NondepTBI, n = 9), depressed mood post-traumatic brain injury patients (DepTBI, n = 26), and normal healthy control subjects (HC, n = 10) were assessed for N100, N200, and P300 latencies and amplitudes by the auditory “oddball paradigm”. DepTBI subjects had significantly prolonged N200 latency and low P300 amplitude compared with the NondepTBI and HC groups. A longer P300 latency in the NondepTBI and DepTBI than in the HC groups was found. A prolongation of N200 latency accompanied by low P300 amplitude may be a characteristic of post-traumatic brain injury patients with depressed mood. Prolonged P300 latency may be more closely associated with TBI than with depression, as it was significantly greater in both the DepTBI and NondepTBI, than in the HC group.     

Confirmation of a relationship between reduced auditory P300 amplitude and thought disorder in schizophrenia

We have previously reported an association between reduced amplitude of auditory P300 event-related potential and severity of positive thought disorder as assessed by the Comprehensive Index of Positive Thought Disorder in a sample of patients with chronic schizophrenia. Here we replicate those findings using a different measure, Thought Disorder Index (TDI), in a new larger sample of 55 patients. The auditory P300 amplitude showed a significant negative correlation with scores on TDI. This correlation was relatively more pronounced in the left temporal region than in the right temporal region. These results further suggest that electrophysiological abnormalities of information processing may underlie positive thought disorder in schizophrenia.     

Interactive ERP recording increases the amplitude of the endogenous P300 peak in schizophrenia

The P300 is a long-latency cognitive event-related potential (ERP) elicited by the presentation of relevant target stimuli. Unfortunately, the standard ERP recording technique takes no account of the background EEG during stimulus presentation. However, a recently developed technique (interactive recording) controls for variability in the EEG by applying stimuli only when the background EEG is in a predetermined state. The use of the interactive technique has led to significant changes in the P300 amplitude in control studies. Since P300 amplitude data are commonly used in schizophrenia research, and have previously been associated with cognitive deficits in schizophrenia, we studied the effects of interactive recording in a schizophrenia population. The same ERP paradigm was implemented twice for each subject, using both standard ERP and the interactive recording techniques. There was a significant increase in the amplitude of the P300 peak with interactive recording, although no significant change in latency. The results indicate that the effect of background EEG may need to be taken into account when conducting general ERP-based studies in schizophrenia. The results also indicate that the method may be used to investigate the effects of EEG variation on ERP values and, by implication, on cognitive processes. In particular, the recognition of EEG states that lead to a higher amplitude ERP value may aid in the further development of EEG investigations of schizophrenia. A similar development is indicated between cognitive research in schizophrenia and the sub-second brain-states in which cognitive function may be reflected.     

Lower P300 amplitude in eight-year-old offspring of alcoholic fathers with a delinquent history

The aim of the present study was to investigate the P300 amplitude as a possible vulnerability marker in children of alcoholic (COA) fathers with and without paternal delinquency. Event-related potentials (ERPs) of 122 children aged 8 years (63 boys, 59 girls) were compared depending on father’s alcoholism subtype: 30 COAs without paternal delinquency, 10 COAs with paternal delinquency, and 82 children of non-alcoholic and non-delinquent fathers. ERPs were recorded from Fz, Cz, and Pz, using an auditory oddball paradigm. Sinus tones of 60 dB HL were presented binaurally at 1,000 Hz (standard stimulus) and 2,000 Hz (target stimulus), at a relative frequency ratio of 80:20. Two trial blocks of 250 stimuli each were collected. Results indicated that only COAs with paternal delinquency displayed significant differences from the control group, characterized by reduced P300 amplitude at frontal site and in the second trial block. Thus, the combination of fathers’ alcoholism and delinquency was more likely to relate to attenuated P300 amplitude in the offspring than paternal alcoholism alone. Our results suggest that both alcoholic and delinquent family history appear to play a role in P300 amplitude reduction in the offspring.     

No decrement in visual P300 amplitude during extended performance of the oddball task

Research indicates that in visual sustained attention paradigms, the amplitude of the P300 component of the event-related potential invoked by target (critical) stimuli shows a decrement in amplitude. This amplitude decrement parallels decrements in vigilance performance that result from the difficult discrimination that is typically required between the infrequent targets and the frequent nontargets (neutral stimuli). In contrast, target stimulus P300 does not appear to show a decrement across large numbers of trials during performance of the "oddball" paradigm, in which targets and nontargets are highly discriminable. The present study measured target and nontarget P300 amplitude during performance of a visual oddball paradigm extended over an interval of some 3 1/2 hours, a period well in excess of the 3/4 hour intervals employed in previous research. The results indicated no decrement in P300 amplitude as a function of time for either targets or nontargets. The only significant relationship between P300 and behavioral data was an inverse correlation across oddball runs between average nontarget P300 amplitude and total number of targets missed.     

ERP amplitude and scalp distribution to target and novel events: effects of temporal order in young,middle-aged and older adults

Event-related brain potentials (ERPs) were recorded from young (mean age = 24.1), middle-aged (48.7) and older (69.7) adults during a version of the oddball paradigm, in which 48 unique, unexpected novel stimuli were interspersed with equally rare instructed targets. As older relative to younger adults are thought to differ in their ability to inhibit the processing of task irrelevant information, we expected, based on previous work, that novel stimuli would retain their ‘novelty’ longer in older than in younger adults. To assess this, P3 amplitude and scalp topography elicited by novels and targets were analyzed as a function of stimulus number (n = 6) within the block and as a function of block number (n = 4). The results were in line with prediction: While the younger adults' P3 scalp distribution shifted from a relatively more frontal to a relatively more posterior focus as a function of novel number within the block, this was not evident in the scalp topographies of the older adults. Coupled with the older adults' elevated false alarm rates to novel stimuli, the data are consistent with a change in frontal lobe function with increases in age.     

Reduction of auditory event-related P300 amplitude in subjects with at-risk mental state for schizophrenia

Neurophysiological methods allow the examination of cognitive-cortical functioning in patients with schizophrenia in its prodromal states. As revealed by previous studies, event-related potential components such as auditory evoked P300 associated with cognitive processes, such as attention and orientation, are known to be reduced in amplitude in acute and chronic as well as in medicated and unmedicated patients. It is, however, unclear whether a P300 amplitude reduction occurs before the schizophrenic psychosis is fully manifested. We studied patients in the prodromal phase of the schizophrenic disorder (i.e. subjects with an at-risk mental state showing attenuated psychotic symptoms or brief limited intermittent symptoms) as well as first-episode patients and chronic patients with schizophrenia and compared these groups to healthy subjects. The event-related P300 was recorded during an auditory oddball paradigm. Groups differed significantly from each other in the P300 amplitude at Pz (F(3/149)=2.532, p=0.02). Post-hoc tests revealed significantly lower P300 amplitudes of non-medicated prodromal (p=.03), first-episode (p=.01) and chronic patients (p=.001) compared to the healthy controls. The study revealed that there are neurophysiological changes as the reduction in P300 amplitudes begins early in schizophrenia at the prodromal phase, i.e. before a manifestation of full-blown psychosis, and that these changes seem to have a progressive course from prodromal to chronic state of schizophrenia as assumed in this cross-sectional study.     

P300 and treatment effect of modafinil on fatigue in multiple sclerosis.

To evaluate the value of visual and auditory P300 for predicting the response of multiple sclerosis-related fatigue to modafinil treatment, 33 patients were treated with 100 mg modafinil once daily for 4 weeks, following a 4-week baseline phase and an optional 8-week extension phase. The main clinical outcome parameter was a decrease in the fatigue visual analogue score (VAS) before and after 4 weeks of treatment. Patients with shorter auditory P300 latency at baseline were more likely to benefit from modafinil treatment. Auditory P300 latency predicted treatment response with a specificity of 76% and a sensitivity of 75% at a cut-off latency of 350 ms. Visual P300 latency could not be used to predict treatment response. Baseline auditory P300 latency predicted treatment response, whereas visual P300 latency did not. Clinical improvement did not correlate with changes in either visual or auditory P300.