Amplitude Of Late Component Research Articles

THE CORRELATIVE ANALYSIS OF AMPLITUDE-TEMPORAL CHARACTERISTICS OF EVOKED POTENTIALS OF BRAIN CORTEX IN SPORTSMEN

The article considers the correlative analysis of amplitude-temporal characteristics of evoked potentials of brain cortex in sportsmen of playing kinds of sport and athletes at perception and processing of significant information “What” and “Where” in the brain cortex. The method of electroencephalography (Р300 methodology) was used to study the evoked potentials of the brain cortex. The statistical processing of data was realized using the statistical package MedStat. Kendall coefficient of correlation was used depending on data distribution, different from the normal values distribution. In the result of research there were revealed the high interconnections of latency of later components in sportsmen of both groups of examined persons at observation of significant stimuli “What” and “Where”. There was revealed the intensification of correlations of latency in frontal, central and temporal parts of the brain cortex. The correlations of amplitude of late components of biopotentials of the brain cortex were characterized with mean coefficients of interconnection mainly in sagittal central frontal and also parietal parts of cortex.

Quality of evidence for perceptual decision making is indexed by trial-to-trial variability of the EEG

A fundamental feature of how we make decisions is that our responses are variable in the choices we make and the time it takes to make them. This makes it impossible to determine, for a single trial of an experiment, the quality of the evidence on which a decision is based. Even for stimuli from a single experimental condition, it is likely that stimulus and encoding differences lead to differences in the quality of evidence. In the research reported here, with a simple "face"/"car" perceptual discrimination task, we obtained late (decision-related) and early (stimulus-related) single-trial EEG component amplitudes that discriminated between faces and cars within and across conditions. We used the values of these amplitudes to sort the response time and choice within each experimental condition into more-face-like and less-face-like groups and then fit the diffusion model for simple decision making (a well-established model in cognitive psychology) to the data in each group separately. The results show that dividing the data on a trial-by-trial basis by using the late-component amplitude produces differences in the estimates of evidence used in the decision process. However, dividing the data on the basis of the early EEG component amplitude or the times of the peak amplitudes of either component did not index the information used in the decision process. The results we present show that a single-trial EEG neurophysiological measure for nominally identical stimuli can be used to sort behavioral response times and choices into those that index the quality of decision-relevant evidence.

CLINICAL STUDY: P3 components of the event‐related potential and marijuana dependence in Southwest California Indians

Native Americans have some of the highest rates of marijuana use and abuse, yet neurobiological measures associated with addiction to marijuana in this population remain unknown. The present investigation evaluated associations between the P350 and P450 components of the event-related potential (ERP) elicited by affective stimuli, and marijuana dependence in a population of Southwest California (SWC) Indian adults. Three hundred and seventeen participants with a mean age of 30 years who were free of major Axis I and psychiatric diagnoses and antisocial personality disorder were categorized as: (1) no marijuana use disorders or other drug dependence diagnoses; (2) marijuana dependence and no other drug dependence diagnoses; and (3) marijuana dependence and other drug dependence diagnoses. ERPs were collected using a facial discrimination task that generated a late positive component with two peaks at approximately P350 and P450 milliseconds. Multivariate analyses of variance was used to detect associations between the two component peaks and the three participant groups taking into consideration age, gender and the presence of a lifetime diagnosis of alcohol dependence. Increases in the latency of both the P350 and P450 component peaks were found to be associated with the diagnosis of marijuana dependence and marijuana dependence co-morbid with other drug dependence. Women appeared to be more impacted than men are. A diagnosis of marijuana dependence was not associated with any changes in late component amplitudes. Taken together these studies suggest that marijuana dependence may be associated with delays in the evaluation and identification of emotional stimuli in SWC Indians.

Excitability changes of hand motor area dependent on afferent inputs induced by different facilitation methods

Motor imagery (MI) and voluntary teeth clenching (VTC) induce excitability changes of hand motor area in primary motor cortex (M1). Additionally, M1 receives thalamocortical and corticocortical afferent inputs. However, relationships between afferent inputs and excitability changes induced by above-mentioned facilitation methods are not clear. Therefore, we investigated whether different effects of MI and VTC occur on early and late I-wave components using transcranial magnetic stimulation (TMS). TMS was applied to the left M1 by antero-medially directed current (to preferentially elicited early I-wave components) and by postero-laterally directed current (to preferentially elicited late ones). Motor evoked potentials (MEPs) were recorded from the right relaxed first dorsal interosseous (FDI) muscle. During MI, MEP amplitudes of late components were significantly larger than those of early ones, although both MEP amplitudes were enhanced. Surprisingly, during VTC, MEP amplitudes of early components were significantly enhanced, but those of late ones were rather depressed. That is, afferent inputs to M1 induced by MI enhanced both early and late I-wave components, but those by VTC have separate influences. Thus, it is assumed that early and late components of I-waves could be differently recruited depending on different afferent input pathways to M1.

A Maximum-Likelihood Estimator for Trial-to-Trial Variations in Noisy MEG/EEG Data Sets

The standard procedure to determine the brain response from a multitrial evoked magnetoencephalography (MEG) or electroencephalography (EEG) data set is to average the individual trials of these data, time locked to the stimulus onset. When the brain responses vary from trial-to-trial this approach is false. In this paper, a maximum-likelihood estimator is derived for the case that the recorded data contain amplitude variations. The estimator accounts for spatially and temporally correlated background noise that is superimposed on the brain response. The model is applied to a series of 17 MEG data sets of normal subjects, obtained during median nerve stimulation. It appears that the amplitude of late component (30-120 ms) shows a systematic negative trend indicating a weakening response during stimulation time. For the early components (20-35 ms) no such a systematic effect was found. The model is furthermore applied on a MEG data set consisting of epileptic spikes of constant spatial distribution but varying polarity. For these data, the advantage of applying the model is that positive and negative spikes can be processed with a single model, thereby reducing the number of degrees of freedom and increasing the signal-to-noise ratio.

Event-related potentials reflect individual differences in age-invariant auditory skills.

Previous work has found that auditory event-related potentials show maturational changes, with latency and amplitude of late components (N1 and P2) decreasing and increasing with age respectively. Our goal was to test the hypothesis that these changes reflect increased speed of neural processing in the auditory system. Thirty-three listeners, aged 10-50 years, were tested on a frequency discrimination task and an auditory backward recognition masking task. P1 and N1b event-related potential components were measured to tones. The N1b became larger and earlier with age, and the latency of P1 decreased with age. However, thresholds on the behavioural tasks did not change with age. Nevertheless, individual differences in the peak amplitude of N1b were independently related to frequency discrimination and degree of masking. Thus, the relationship that does exist between individual differences in psychoacoustic performance and the auditory N1b reflect a stable characteristic of the individual rather than a maturational change.

EEG correlates of finger movements with different inertial load conditions as revealed by averaging techniques

Objective: The present study was aimed to further address the general empirical question regarding the sensitivity of EEG correlates toward specific kinematic and/or kinetic movement parameters. In particular, we examined whether adding different inertial loads to the index finger, while a subject produced various amplitudes of discrete finger movements, influenced the movement-related potentials (MRP).Methods: Our experimental design systematically controlled the angular displacement, velocity and acceleration (kinematic) profiles of finger movement while torque (kinetics) was varied by adding different external loads opposing finger flexion movement. We applied time-domain averaging of EEG single trials in order to extract three movement-related potentials (BP−600 to −500 BP−100 to 0 and N0 to 100) preceding and accompanying 25, 50 and 75° unilateral finger movements with no inertial load, small (100 g) and large (200 g) loading.Results: It was shown that both inertial load and the degree of angular displacement of index finger flexion increased the amplitude of late components of MRP (BP−100 to 0 and N0 to 100) over frontal and precentral areas. In contrast, the external load and movement amplitude manipulations did not influence the earlier component of the MRP (BP−600 to −500).Conclusions: Overall, the data demonstrate that adding inertial load to the finger with larger angular displacements involves systematic increase in activation across frontal and precentral areas that are related to movement initiation as reflected in BP−100 to 0 and N0 to 100.

Spatiotemporal distribution of a late synchronized activity in olfactory pathways following stimulation of the olfactory bulb in rats.

The evoked potential recorded in the rat piriform cortex in response to electrical stimulation of the olfactory bulb is composed of an early component occasionally followed by a late component (60-70 ms). We previously showed that the late component occurrence was enhanced following an olfactory learning. In the present study carried out in naive rats, we investigated the precise conditions of induction of this late component, and its spatiotemporal distribution along the olfactory pathways. In the anaesthetized rat, a stimulating electrode was implanted in the olfactory bulb. Four recording electrodes were positioned, respectively, in the olfactory bulb, the anterior and posterior parts of the piriform cortex, and the entorhinal cortex. Simultaneous recording of signals evoked in the four sampled structures in response to stimulation of the olfactory bulb revealed that the late component was detected in anterior and posterior piriform cortex as well as in entorhinal cortex, but not in the olfactory bulb. The late component occurred reliably for a narrow range of low intensities of stimulation delivered at frequencies not exceeding 1 Hz. Comparison of late component amplitude and latency across the different recorded sites showed that this component appeared first and with the greatest amplitude in the posterior piriform cortex. In addition to showing a functional dissociation between anterior and posterior parts of the piriform cortex, these data suggest that the posterior piriform cortex could be the locus of generation of this late high amplitude synchronized activity, which would then propagate to the neighbouring regions.

Event-related potentials in drug-naive schizophrenic patients

Decreased amplitudes of late components of event-related potentials (ERPs) in schizophrenia were ascribed to either psychotic features or to neuroleptic treatment of the patients. To rule out the drug effect, ERPs to stroboscopic stimuli were recorded in drug-naive schizophrenics and control subjects during no-task and simple-task sessions. Patients had significantly lower amplitudes of the late ERP components during both sessions, thus confirming similar results with treated schizophrenics. On the other hand, drug-naive patients did not differ from controls in the task-related relative facilitation of late ERP components. These results differ from findings of minimal ERP facilitation to task in treated schizophrenics. This discrepancy is discussed in the context of the effects of neuroleptic treatment and task demands on ERPs.

Multimodal effects of acute exposure to toluene evidenced by sensory-evoked potentials from Fischer-344 rats

Male Fischer-344 rats were exposed by inhalation to 500, 2000, 5000, 8000 and 16000 ppm toluene for 30 min in two experiments. Exposures up to 8000 ppm in Experiment 1 caused concentration-related changes in the click-elicited brainstem auditory-evoked response (CBAER), flash-evoked potential (FEP) and somatosensory-evoked potential (SEP). Latencies of CBAER components were prolonged and amplitudes of late components were increased by toluene. Toluene did not detectably alter the latencies of FEP or SEP components. Early FEP component-amplitudes were increased and late component-amplitudes were decreased; toluene also induced a poststimulus oscillation in the FEP. Most component-amplitudes of the SEP were substantially increased, but N2P2 amplitude appeared to be more sensitive than other components to depressant effects of the solvent. The same effects on the CBAER were observed in Experiment 2, but a more substantial increase in the amplitudes of late components elicited by tone pips suggested that frequency-dependent cochlear irritation might underlie previously observed subchronic ototoxicity. These effects were increased by exposure to 16000 ppm toluene. Effects like those observed in Experiment 1 were noted on the FEP, but the oscillations were less with exposure to 16000 than 8000 ppm. Changes in the SEP were evident within 2 minutes of exposure onset, and amplitudes increased over the course of about 15 min, leveling off or decreasing thereafter. The amplitude of the N2P2 component was again less influenced than other components during exposure to 8000 ppm and was reduced to less than baseline amplitude by 16000 ppm. Effects of concentration and rates of development and recovery were systematically related to SEP component latency. Toluene appears to have both enhancing and inhibiting effects on neural pathways serving sensory systems, depending on the modality and the site of generation of the components within modalities. A particular balance between these properties might relate to the hedonic characteristics of this abused solvent.

Chronic exposure of primates to 60-Hz electric and magnetic fields: III. Neurophysiologic effects.

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.

Auditory event-related potentials in children at risk for schizophrenia: The complete initial sample

Event-related potentials (ERPs) were recorded from children of schizophrenic parents, children of parents with affective disorders, and children of parents without a history of psychiatric illness. ERPs were elicited during a modification of the “oddball” paradigm, in which two infrequents (a change in pitch and a missing stimulus) were embedded in a series of frequent background events. The data were recorded from electrodes located at midline frontal, central, parietal, and occipital scalp sites. Diagnostic assessments of the parents were performed using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version (SADS-L) and Research Diagnostic Criteria (RDC). Behavioral assessments of the children were made with a modified version (BGAS) of the Global Assessment Scale. ERP amplitudes for several electrophysiological events were compared among groups for target and nontarget stimuli using analyses of variance of both factor score and baseline to peak measures. No systematic differences suggesting waveform abnormalities in the children of schizophrenic parents (high-risk subjects) were found. However, when the results were analyzed using only those children whose parents had a “pure” diagnosis of either schizophrenia or affective disorder, the children of affectively disordered parents (psychiatric control subjects) showed significantly lower N100 amplitudes (to the frequent event only) than either the normal control or high-risk subjects. No consistent behavioral differences among the three groups emerged. Since only a small percentage of children at risk will eventually develop schizophrenia, ERP amplitude frequency distribution analyses were also performed and compared among groups. However, these did not provide evidence of an outlying subgroup in any of the three groups. There were complex relationships between ERP component amplitudes and behavioral adjustment in adolescence but, in general, these did not distinguish high-risk and psychiatric control subjects from each other. There was no evidence of a relationship between deviant attentional functioning as measured in an earlier round of laboratory testing and ERP late component amplitude.

Cortical evoked potentials and clinical rating scales as measures of depressive illness.

Relationships between clinical ratings and cortical evoked potentials were examined before and during antidepressant drug treatment in 32 patients with major depressive disorder (DSM-III). Clinical rating scales included Hamilton Rating Scale for Depression, Beck Depression Inventory, Present State Examination (PSE) and Newcastle Scale. Evoked potentials included contingent negative variation (CNV), post-imperative negative variation (PINV) and auditory evoked potential (AEP) There were close correlations between all rating scales, and factor analysis produced only one component, suggesting that the common variance between them related to severity of depression. CNV magnitude before treatment correlated negatively with severity of depression regardless of diagnostic category. Depressed patients had a prominent PINV which persisted during antidepressant treatment. The amplitude of late components (N1P2) of the AEP was reduced strikingly in patients with a history of suicide attempts.

Late positive component amplitude in schizophrenics and alcoholics in two different paradigms

Abstinent alcoholics, unmedicated schizophrenics, and controls were tested in two paradigms designed to elicit the late positive component. Experiment A used frequent stimuli of differing incentive value and Experiment B used infrequent stimuli of differing perceptual discriminability. Alcoholics and schizophrenics showed late positive components that were significantly reduced in amplitude compared to controls. The patient groups were similar in their late component amplitudes. Control subjects showed a substantially wider response range than the patient groups. The narrow response range in both patient groups was manifested in diminished late component amplitudes to both stimuli in both experiments. The intraclass correlation coefficient of late component amplitudes for both patient groups was significantly greater than that of the controls.

Alteration by Enflurane of Electrophysiologic Correlates of Search in Short-term Memory

Effects of controlled subanesthetic concentrations of enflurane on short-term memory functions and associated scalp evoked potentials were studied in eight male volunteers. Short-term memory processes were assessed through a search task. A series of digits (one, three, five, seven, nine, or 11 digits in each series) was presented visually, followed by a test digit, which in half of the trials was part of the series, and in half of the trials was not. The subject responded by pressing one of two switches, signalling "yes" or "no" accordingly. Averaged evoked potentials elicited by the test digit were obtained from seven sites on the scalp. End-tidal enflurane concentrations between 0.12 and 0.25 per cent increased significantly by 30-40 msec the latency of the components of the evoked potentials reflecting sensory processing, but did not affect their amplitude significantly. This increase could not explain the 287-msec increase in reaction time. Amplitude of late components of the averaged potential reflecting information processing was markedly decreased, which the authors interpret as indicating increased trial-to-trial variation in latency of the late component. The authors conclude that enflurane delays and introduces variance into the short-term memory processes and subsequent decision processes that preced overt responses.

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.

Interrelationships of hippocampal EEG and visual evoked responses during appetitive behavior in rats

Summary Averaged visual evoked responses (VERs) at the cortex to flashes and hippocampal (HPC) electrical activity were examined during different phases of bar-pressing for sucrose solution on a fixed-ratio schedule. Systematic variations were found in amplitude of late components of VERs. The late components were largest during reinforcing consummatory behavior, smallest during the postreinforcement period, and intermediate during bar-pressing. Further analysis of VERs within each bar-press sequence revealed increased amplitude of late components as the animal progressed through the sequence. These orderly changes in VERs related closely to hippocampal EEG which also varied systematically during different phases of appetitive behavior. The average frequency of synchronous HPC activity related inversely to amplitude of VER late components. Analysis of synchronous HPC activity during 1-sec epochs before and after each flash revealed strong negative correlations between these measures and late negative and afterdischarge components of the VER. These findings, which indicate significant interrelationships among sensory evoked response, hippocampal EEG activity and associated behavioral patterns of activity, were viewed in terms of the plasticity of operation of electrophysiological arousal systems.

Facilitated habituation: strychnine dose-response effects on neural and behavioral habituation.

The effects of two doses of strychnine sulfate (0.125 mg/kg and 0.500 mg/kg) on mouse neural and behavioral habituation were assessed. Reliable alterations in concurrent neural (spontaneous and evoked) activity and spontaneous behavioral activity were obtained as the result of training. Neural habituation was characterized by higher frequency, lower amplitude EEG activity, reduced hippocampal theta activity, increased amplitudes in early components of visual evoked responses, and transient increases followed by progressive decreases of late component amplitudes of the visual evoked responses. Behavioral habituation appeared as decreased gross activity and changes in mouse orientation to cogent features of the test chamber. Low strychnine doses (0.125 mg/kg) reliably facilitated habituation to light flashes and produced lessened sensitivity to dishabituation stimuli. High strychnine doses (0.500 mg/kg) disrupted habituation and produced heightened sensitivity to dishabituation stimuli. The results were accommodated by a modified dualprocess theory of habituation; single process views of habituation were inadequate. The significance of these results to drug facilitation was discussed in terms of optimal arousal and the mediation of pro- and retroactive influences on learning. The characterization of processes underlying memory storage seems amenable to further clarification using CNS stimulants known to operate on such processes.