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Results for “Event-Related Potentials, P300”

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At least 19 recordsLinked to original sources

PubMed1992

P300 event-related potentials correlated with cerebral blood flow in nondemented patients with lacunar infarction.

We have studied the relationship between the P300 latency and regional cerebral blood flow (rCBF) in 25 nondemented patients who had lacunar infarctions in the territory of the deep perforating branches of the internal carotid artery system. A significant prolongation of the P300 latency with advancing age was observed. There was a negative correlation between the P300 latency and the rCBF. These results indicate that a combination of P300 latency and rCBF measurements might prove more sensitive in detecting mental decline than rCBF studies alone in nondemented patients with lacunar infarctions.

Adult↗

PubMed1975

On the independence of the CNV and the P300 components of the human averaged evoked potential.

We report an experiment designed to assess the interactions between the CNV and the P300 components of human event-related potential. Eight subjects were each presented with series of experimental trials on all of which either a 1200 c/sec or an 800 c/sec tone was presented. There were three independent variables: (a) The presence or absence of a warning flash 1000 msec prior to the tone. (b) The task assigned to the subject--that is subjects were either to make a discriminative response to the tone or, on half the series, to predict prior to the tiral which of the two tones would be presented. (c) The predictability of the tone frequency. On half the series high and low tones alternated from trial to trial. On the other series, tones were chosen randomly on each trial. The data show that the amplitude of the P300 component is not affected by the presence or absence of a warning stimulus. Furthermore, the distributions of P300 and the CNV over the scalp are quite different. These conclusions are supported by a principal component and a discriminant analysis of the data. We conclude that the CNV and the P300 reflect the activity of functionally distinct cortical mechanisms.

Analysis of Variance↗

PubMed1992

Differential effects of voluntary expectancies on reaction times and event-related potentials: evidence for automatic and controlled expectancies.

Expectancy has been used to explain the effects of stimulus sequences both on reaction times (RTs) and on the P300 component of the human event-related potential. However, there are conflicting views about the control obtainable over these underlying expectancies. We compared the effects of voluntary expectancies for stimulus changes or repetitions in random tone series on RTs and the P300. Ss responded according to either stimulus identity (Experiment 1) or stimulus sequence (Experiment 2). In both experiments RTs were strongly affected by event expectedness. P300 amplitude, on the other hand, was affected (as a trend) only in Experiment 2. The results suggest that there are at least 2 types of "expectancy", one that is largely automatic and inflexible, reflected in P300 amplitude, and a second, controlled process that is reflected mainly in RT. The latter type of expectancy appears to affect processing stages beyond stimulus evaluation and classification.

Arousal↗

PubMed1977

Augmenting mental chronometry: the P300 as a measure of stimulus evaluation time.

A technique for measuring the latency of the P300 component of event-related brain potentials on individual trials is described. Choice reaction times and the latency of the P300 were compared under speed-maximizing and under accuracy-mazimising instructions. The choice stimuli required different levels of semantic categorization. The data support the proposition that the latency of P300 corresponds to stimulus evaluation time and is independent of response selection.

Brain↗

PubMed1978

On how P300 amplitude varies with the utility of the eliciting stimuli.

The bulk of the relevant evidence indicates that stimuli which elicit the P300 component of the human event-related potential (ERP) tend to be unexpected and task relevant. Yet, contradictory evidence has been presented which implied that P300 amplitude is modulated by the intensity difference between two equally relevant, equally probable feedback stimuli (Adams and Benson, 1973). The two experiments reported here were designed to clarify this contradiction. Subjects were instructed to press a button one second after a cue light. A tone at one of two intensities was presented 200 msec later indicating whether the time estimate was 'correct' or 'incorrect'. The magnitude of P300 varied as a function of the difference in intensity between S+ and S-; the smaller the difference, the smaller was P300, regardless of stimulus meaning (S+ or S-). We attribute this effect to the degree to which the subject chooses to utilize the tones in the performance of the time estimation task. In support of this hypothesis, we found that performance of the subjects as time estimators degraded as the difference between S+ and S- decreased. Moreover, a study of choice reaction times taken for the different pairings of S+ and S- showed that the stimulus pairs were not equally discriminable. It appears that as the S+/S- pairs become increasingly difficult to discriminate, their feedback value decreased and this decrease is positively correlated with a decrease in P300 amplitude. This interpretation received support from Exp. 2 in which the stimulus conditions were the same as in Exp. 1, but the subject's task was to count the "s+ stimuli. Here, when subject had no option but to process each individual stimulus, the P300 amplitude remained constant despite variations in S- intensity. Thus, it appears that task relevance must be defined in terms of the subject's behavior rather than by the experimenter's instructions to the subject.

Acoustic Stimulation↗

PubMed1979

The independence of the P300 and the CNV reviewed: a reply to Wastell.

The relationship of P300 to the CNV was investigated by Donchin, Tueting, Ritter, Kutas and Heffley (1975) who concluded that these two components of the event-related brain potential (ERP) are independent. Wastell (1979) questioned the validity of the data analysis procedures and of the experimental design used by Donchin et al. In this report we examine Wastell's criticisms and find them to be unfounded. In support of this conclusion we note the differences between principal component analysis and factor analysis. We clarify points about Donchin et al.'s experimental design, and we review evidence for the independence of the P300 and the CNV that has accumulated since 1975.

Contingent Negative Variation↗

PubMed1992

Acute effects of alcohol on cognitive function and central nervous system assessed by auditory event-related potentials.

To clarify which sites of the central nervous system are influenced by acute administration of alcohol at an early stage, auditory event-related potentials (ERP) using a target-selection paradigm were measured in 13 healthy volunteers. In the recorded waveforms of ERPs, the N100, P165, N200 and P300 latencies for the target tone and the N100 and P200 latencies for the non-target tone were determined in each subject before and 1- and 2-hr after ingestion of 200 ml of alcohol (containing 25% ethanol) or of 200 ml of water, for a total of six times on two different days. The P300 latency was significantly prolonged at 1- and 2-hr after alcohol ingestion; and, the N200 latency was significantly prolonged at 2-hr after alcohol ingestion. The 2-hr alteration in the P300 latency after alcohol ingestion was positively correlated with the ethanol dose per body weight. These data suggest that ethanol, in proportion to its dose, affects cognitive function estimated by the P300 latency earlier than other lower central nervous system functions. Evaluating subclinical effects on central nervous function, using the ERPs, of environmental neurotoxins such as organic solvents, researchers should pay particular attention not only to the degree of the drinking habit but also to the interval between the measurement and alcohol intake.

Adult↗

PubMed1978

EEG event-related potentials and signal detection.

The purpose of this study was to determine whether certain previously reported relationships between event-related potentials and measures of signal detection performance occur in vigilance as well as psychophysical settings. In the course of the study, evidence was found which challenges previously proposed psychological correlates of "P300". EEG was recorded while 15 subjects carried out a 40-min signal detection test. CNV was measured between a warning click and the brief offset of a dim light denoting the possible (p = 0.5) occurrence of the signal, a faint tone in the constant background noise. P300 was measured at a point 300 msec following offset of the dim light. As reported previously in psychophysical settings, P300 amplitude was positively related to signal intensity and response confidence, and was larger for correct detections (Hits) than for correct rejections, misses or false alarms. From first to second half of the test both Hits and false alarms fell, response criterion beta rose, and the amplitude of both CNV and P300 fell. The latter negative relationship between beta and P300 contrasted with a positive one when subjects rated their signal reports at three levels of confidence; here the most confident ratings (high beta) were associated with the highest amplitude of P300. CNV reflected individual ability to sustain performance. Results are explained in terms of a two-factor version (Wilkinson, 1976) of the prior state/reactive change hypothesis (Karlin, 1970). It is suggested that time on task constitutes a prior state influence on P300, whereas other variables influence P300 by means of either reactive change or 'real' change in an endogenous P300 component.

Adult↗

PubMed1992

The scalp topography of P300 in the visual and auditory modalities: a comparison of three normalization methods and the control of statistical type II error.

This study was designed to replicate recent findings suggesting that the P3 component of the event-related potential is dependent on the modality of the eliciting stimulus. When assessing this research hypothesis two methodological problems are of special interest: first, the amplitudes have to be normalized, due to problems with the model of the analysis of variance; second, special care has to be taken regarding the beta error, which is the probability of falsely accepting the null hypothesis of a statistical test. A possible modality independence is associated with the acceptance of a null hypothesis. The first problem was assessed by using different normalization procedures and comparing their results. The second was solved by controlling the beta error. Results for P3 amplitudes from two sessions in which 61 subjects performed in each session an auditory and a visual oddball task (EEG measured at 11 locations) showed no influence of modality on the P3 elicited by the rare, task relevant, stimulus. Influences of modality were observed for the P3 elicited by the frequent stimulus. As it is quite unlikely that P3 generating sources are strongly active during the processing of the frequent stimulus, this effect is possibly due to a component overlap from the vertex potential.

Adult↗

PubMed1978

The effect of warning stimulus novelty on the P300 and components of the contingent negative variation.

This experiment evaluated the effects of stimulus and response probability on the P300 and components of the contingent negative variation (CNV) in three different reaction tasks. In the first task the warning stimulus (S1) indicated that the imperative stimulus (S2) would require either a left or a right button press response; in the two other tasks the S1 indicated that S2 would either require a button press response or not. The a priori probability of S1 and the response to S2 were independently varied. The results show that a novel S1 significantly increased the amplitude and latency of the P300 and early CNV component: the late CNV component, however, increased significantly when a motor response to S2 was required. Early and late CNV components also differed in midline distribution. It is concluded that the early CNV can be viewed as the slow wave part of the event-related potential to S1, while the late CNV is an event preceding shift that strongly relates to the motor requirements of S2. It is finally suggested that both the P300 and early CNV reflect an orienting response to S1.

Acoustic Stimulation↗

PubMedDate not supplied

Somatosensory event-related potentials following different stimulus conditions.

We studied somatosensory event-related potentials (ERPs) in response to rare target, frequent nontarget and rare nontarget stimuli in 12 healthy subjects. Compared with the corresponding peaks following frequent stimuli, the responses elicited by rare target stimuli showed higher amplitudes for N70, P100 and N140 components and those evoked by rare nontarget stimuli showed higher amplitudes for N70 and N140 components. The P300 component following rare nontarget stimuli was shorter in latency and lower in amplitude than that elicited by target stimuli. ERP waveforms evoked by rare nontarget stimuli also showed obvious N240 and P300 components, which differed from those following frequent nontarget stimuli. These findings suggest that there are differences in signal processing in response to target, frequent nontarget and rare nontarget stimuli. The P300 component was distributed symmetrically and there was no significant hemispheric predominance with regard to any ERP component in response to either right or left side stimulation.

Adult↗

PubMed1977

Active touch exploration of extrapersonal space elicits specific electrogenesis in the right cerebral hemisphere of intact right-handed man.

Language and analytic processing are currently thought to be represented in the left hemisphere, whereas spatial and holistic processing would involve primarily the right hemisphere in man. An experimental paradigm for engaging the nonlanguage hemisphere (generally the right) is described. This involves active touch exploration with the index finger to identify the orientation of a ridge with respect to the subject's body. The task is compatible with the electronic averaging of transient event-related cerebral potentials recorded from the intact scalp. A consistent positive electrogenesis of 1-5 muV and about 0.5-1.5 sec in duration was recorded over the nonlanguage hemisphere, regardless of whether the left or the right index finger performed the tactile scanning. The lateralized specific electrogenesis did not extend to the midline, and it is to be differentiated from the decision P300 component. These findings provide a new procedure for analyzing, in intact man, measurable focal potentials associated with unique processor subsystems during cognitive behavior. The method will make it possible to investigate the dynamic distribution of processing tasks between the two hemispheres in normal man in whom the commissural integration is normal, thereby adding to the data collected on patients with unilateral brain lesions or with surgical transection of the corpus callosum.

Adult↗

PubMed1992

Potentials associated with the initiation and inhibition of visually triggered finger movement in humans: the "no-go potential" in the go/no-go paradigm.

Surface event-related potentials associated with visually triggered movements (Go) and the inhibition of planned movements (No-Go) of the right index finger were examined in seven normal healthy subjects. Subjects' response priming was manipulated by presenting two sessions which either emphasized the Go condition (50 go trials vs. 30 no-go trials) or the No-Go condition (30 go trials vs. 50 no-go trials). Stimulus-locked waveforms showed enhanced components (P1-N1, N2, N1-P300) for the No-Go trials particularly in the response priming which emphasized the Go condition. It is suggested that the inhibition of planned movements is associated with surface negativity which trails the sensory P1-N1 potential yet may partially overlap it and therefore influence its amplitude. This "no-go" potential is dependent on the response priming of the subject and is most apparent when fast responses are planned and then arrested.

Adult↗

PubMedDate not supplied

Event-related potentials in a guessing task: the gleam in the eye effect.

Event-related potentials (ERPs) were recorded from a single subject performing a forced-choice guessing task. On each trial, ERPs were elicited by four, sequential, graphic images; 2 1/2 seconds after the last stimulus was delivered, the subject guessed which of the four images was experimentally (randomly) designated as the target. P200 had greater amplitude over the posterior scalp for stimuli which were guessed by the subject to be targets than for not-guessed stimuli. The amplitude of the P100, N100, and P300 components was unrelated to the subject's guess. A positive displacement evident in the waveforms from about 150-500 ms post-stimulus onset suggested that Slow Wave may have been partially responsible for the observed differences. These results suggest that ERPs may contain predictive information about a subject's subsequent responses in forced-choice guessing tasks. We termed this the "gleam in the eye" effect.

Arousal↗

PubMed1992

Endogenous event-related potentials as indices of dementia in multiple sclerosis patients.

Auditory event-related potentials (ERPs) were recorded in a "double oddball" paradigm requiring an easy and a hard pitch discrimination from multiple sclerosis (MS) patients with and without dementia, and a group of age and sex matched normal subjects. Cognitive function was assessed by a short battery of neuropsychologic (NP) tests, and the two groups of MS patients were selected on the basis of substantial non-overlapping degrees of cognitive deficit in the demented as compared to the non-demented group. The N100, P200 and P300 ERP components were longer in latency in the demented patients, and the N100-P300 interval was prolonged as well, compared to the non-demented patients, whose ERP latencies did not differ from those of the normal subjects. Increased P300 latency was associated with poorer performance on the NP tests, especially those sensitive to impairment of learning and retrieval from memory. The reaction times of both patient groups were prolonged as compared to the controls, whereas the accuracy of the demented patients was significantly poorer than that of the non-demented patients.

Adult↗

PubMed1978

Stimulus and response related components of the late positive complex in visual discrimination tasks.

Visual event-related potentials (ERP) were recorded from 6 subjects aged 10--15 in response to target stimuli in 2 vigilance tasks which differed in their processing requirements. Stimulus- and response-synchronized averages were computed for each subject for each quartile (Q) of that subject's reaction time (RT) distribution. Late positive complexes (LPC) of identical morphology were seen in the brain potentials from each task. In Q1, the LPC was an undifferentiated, large amplitude, positive-going potential with a parietal-maximum topography. As RT increased, the LPC became increasingly differentiated so that by Q3 3 components in the latency range of P300 were visible: two constant-latency peaks, P286 (fronto-central), P341 (parietal); and one variable-latency deflection, P539 (parietal), whose peak latency lengthened as RT increased. An additional constant-latency peak, P198, was also recorded. Principal component analyses of the averaged wave forms confirmed the visual identification of these components. The fixed-latency peaks identified in the brain potentials of these subjects were similar in timing and topography to previously reported late positive components. This study demonstrated. however, that the LPC can be segregated into stimulus-related and response-related components.

Adolescent↗

PubMed1992

Relation of a negative ERP component to response inhibition in a Go/No-go task.

Previous studies have suggested that a negative component (N2) of the event-related potential (ERP), whose peak latency is 200-300 msec after stimulus onset, may vary in amplitude depending on the neuronal activity required for response inhibition. To confirm this, ERPs were recorded in a Go/No-go paradigm in which subjects of one group (HI, n = 10) were asked to respond to Go stimuli with key pressing within a shorter period (less than 300 msec) than those of the other group (LI, n = 10) whose upper limit of the reaction time was relatively longer (less than 500 msec). All subjects had to withhold the Go response to the No-go stimuli without making overt muscle activities. The N2 component was recorded superposed on the initial descending limb of the P300 and other slow deflections, which were attenuated with a digital filter to measure the amplitude of N2. The N2 amplitude was significantly larger to the No-go stimulus than to the Go stimulus in both groups, but the N2 to the No-go stimulus was significantly larger in the HI group than in the LI group. These differences in N2 amplitude between conditions or groups were thought to be independent of other ERP components such as P300 and CNV. These results suggest that at least to some extent N2, which increased in amplitude when a greater effort was required to withhold the Go response, reflects the activity of a response inhibition system of the brain.

Adult↗

PubMed1992

Background EEG reactivity in auditory event-related potentials.

Mental activity has influences on auditory event-related potentials (AERP) as well as on some EEG rhythms, notably the alpha rhythm. In this study, background reactivity (BR) of the EEG was investigated in the context of AERPs. Single responses of 14 healthy subjects were analysed in 3 reaction time AERP experiments of increasing difficulty: the first involved one type of tone delivered at random intervals, the second offered two types of tone (an "oddball" design), and the third offered 3 types of tone. Averages were formed and subtracted from the separate responses to reduce their contribution to the EEG. The 1526 msec EEG epoch was divided in 9 overlapping periods, and averaged power spectra were calculated for these periods. Changes in area of the delta, theta, alpha and beta bands in the course of the epoch were calculated. Background alpha and beta activity decreased following infrequent but not following frequent tones. The decrease was larger for more difficult tasks and reached a maximum in the period in which the AERP P3 and N3 peaks fell. Delta and theta powers showed increases rather than decreases; these could be attributed to the contribution of AERP activity to total EEG power. No clear relationships were found between the amount of background reactivity and peak latencies or reaction times. The occurrence of background reactivity, not apparent in an average, shows that the averaged AERP reveals only part of the EEG changes related to mental activity. Background reactivity proved to be more sensitive to task difficulty than P300 latency. The results are discussed in the context of the additive model of evoked potentials.

Acoustic Stimulation↗