Method for recording short latency evoked potentials using an EKG artifact elimination procedure

This paper describes the application of an EKG elimination procedure¹, previously reported by the authors, to evoked potentials (EPs) recording using a non-cephalic reference. The method consists of three separate steps: data acquisition, EKG artifact elimination, and EP averaging. EKG artifacts are eliminated from the raw EEG by applying a four step procedure to the simultaneously recorded EEG, EKG and stimulus pulse. The steps are: synchronized partition of the raw EEG, EKG averaging, synchronized repetition, and synchronized subtraction of the EKG estimate from the raw EEG. Average EP values are then obtained by averaging the processed EEG using the stimulus pulse as a trigger. Somatosensory evoked potentials to a hand reference, averaged using the proposed method, were compared with those obtained by two conventional averaging methods, and were shown to be more clearly defined. The advantage of the proposed method for recording short latency EP values with a non-cephalic reference is that it requires fewer sweeps and thus takes less time than other methods. The proposed method may also be applicable to the recording of other EP values.     

Brain bioelectrical activity at a high anxiety level in humans

Brain bioelectrical activity was studied in 38 and 34 subjects with high and low levels of anxiety, respectively, by means of toposelective mapping of EEG spectral power and recording of P300 endogenous event-related auditory evoked potentials (EPs). Analysis of EEG spectra demonstrated, in the subjects with a high level of trait anxiety, a higher power of β₁ oscillations in the central-parietal areas of both hemispheres and the occipital area of the right hemisphere, as well as a higher power of θ and α oscillations in the frontal areas of both hemispheres and the central-parietal area of the left hemisphere. The occipital-frontal gradient of the spectral power of these rhythmic EEG components was altered in subjects with a high level of trait anxiety. Comparison of P300 cognitive auditory EPs in the subjects with high anxiety and in the control group showed that, in the former, the P300 EP amplitude and the habituation distortion (dishabituation) of the P300 EP amplitude were significantly higher in both hemispheres. This indicates that, at a high level of anxiety, the active directed attention was disturbed, which is confirmed by the results of neuropsychological examination, demonstrating reduced selectivity, concentration, and stability of attention in the Münsterberg test and Schulte’s test. The results of electrophysiological examination suggest that the malfunction of regulatory brain modulating systems is an important neurophysiological mechanism of attention pathology and disturbed adaptation in subjects with a high level of trait anxiety.     

Retention of orienting reaction habituation in chronic alcoholics

A polygraphic study on resistance to habituation of the somatic (EMG), autonomic (finger plethysmogram, galvanic skin reaction, respiration) and EEG (acoustic-evoked potential and EEG-blocking reaction) components of the orienting reaction, elicited by a repetitive auditory stimulus during successive (weekly) sessions was performed in 67 chronic alcoholics and in 70 matched normal subjects (control group). The study showed significant retention disturbances of orienting reaction habituation (i.e., of learning), or the "saving" of stimulations, achieved from one session to the other to obtain the habituation criterion, the savings being less in alcoholics than in control subjects. The severity of habituation retention disturbances depended on patients' ages, types of alcoholism, alcohol consumption intensity and chronicity, as well as the type of resting EEG.     

Habituation of auditory evoked potentials and emotional state

"Fast" and "slow" habituation of N1 and N1-P2 components of auditory evoked potentials was studied in healthy subjects and in depressed patients. In patients, initially more low amplitudes of N1 and N1-P2 were revealed, as well as slowing down of habituation in the beginning of stimuli series and acceleration to its end (in healthy people--the greatest habituation in the initial part of the series and amplitude increase at its end), the absence of power effect in the component N1 at reaching, in the process of habituation, of the same minimum parameters as in healthy subjects. This points to weakening of dishabituation process parallel with well expressed "slow" habituation in patients and allows to suggest at expressed negative emotions a deficit of attention processes as a result of "internal abstraction".     

Cerebral evoked potentials after rectal stimulation

We obtained reproducible cortical evoked potentials (EPs) in response to electrical stimulation of the rectum with 1 Hz frequency. We found 2 distinctly different EPs in response to rectal stimulation. In 5 females, the EP had an early onset latency (mean 26 msec) with multiple positive and negative peaks. In 10 females, the EP had a later onset latency (mean 52 msec) and a trifid configuration, having a very prominent negative peak. The early onset EPs after rectal stimulation appeared very similar to the wave form of the cortical EPs recorded after pudendal nerve stimulation. Finding similar interpeak latencies in the early onset EP after rectal stimulation and the EP after pudendal nerve stimulation suggests that either the same pathway was used or that rectal stimulation also stimulated the pudendal nerve. It appears that we stimulated visceral afferents when we recorded late onset EPs, because the large EP amplitude declined rapidly with faster stimulation rates and also with greater number of averaging, and the sensation threshold was very unstable, all different to somatosensory EPs.     

Habituation of orienting reaction in night terrors

A polygraphic study on resistance to habituation of the somatic (EMG), autonomic (finger vasoconstriction, galvanic skin reaction, respiration, pulse) and EEG (acoustic-evoked potential, EEG-blocking reaction) components of the orienting reaction elicited by a repetitive auditory stimulus was performed in 36 patients with night terrors and in 72 matched subjects in two control groups. The study evidenced a significantly higher resistance to habituation of the orienting reaction in patients with night terrors than in normal subjects (control group I) but significantly lower than in patients with symptomatic epilepsy (control group II). The severity of these habituation disturbances in patients with night terrors depended on the patients' age, the history of nocturnal events and their clinical form, as well as on the etiology of episodes. The habituation changes found in patients with night terrors may be ascribed to the nervous disorders of functional and/or organic nature which generated also the night terrors episodes.     

Impairment of space-frequency parameters of EEG coherence during cognitive performance (consequences of Chernobyl accident)

Changes in frequency and space parameters of the EEG coherence evoked by cognitive performance were analyzed in 13 healthy subjects and participants of the Chemobyl clean-up. In healthy subjects, the EEG coherences in the alpha and beta frequency bands were significantly increased during arithmetic count and during visuospatial performance. Each test was characterized by regionally-specific features. Chemobyl patients demonstrated a global decrease in the EEG coherence predominantly in the alpha and beta frequency bands, especially in the frontal cortical areas. Patients with various pathological EEG patterns demonstrated specific impairment of EEG parameters. In patients with a "flat" EEG pattern, the EEG coherence predominantly decreased in the frontal associative areas, especially during arithmetic calculation. In patients with a "hypersynchronous" EEG pattern, the decrease in the EEG coherence was most pronounced in the parietal associative areas, especially during the visuospatial performance. The revealed impairments of the EEG coherence reactivity may be a reflection of disorders of the intracortical and corticosubcortical interaction and can result from the remote postradiation brain atrophy, especially, of cortical structures.     

Method for single-trial recordings of somatosensory evoked potentials

Evoked potentials (EPs) in response to stimuli are recorded from a human scalp contaminated with noise. To improve the signal-to-noise ratio, averaging methods have been widely used for the recorded data. However, when the waveforms of EP for each stimulus are not identical, the average waveform of the EP deteriorates. Variation of the EP waveform to each stimulus itself is important information for the EP. In this paper, a recording method for single somatosensory evoked potential (SEP) waveform is proposed, in which three kinds of band-pass filters were selectively used during three specific time sectors for each interstimulus interval. For the late section of the interval, an EEG waveform prediction method was applied to eliminate contaminated alpha rhythm components. By using the proposed method, we were successful in detecting the single SEP waveform.     

Transfer of habituation in Aplysia: contribution of heterosynaptic pathways in habituation of the gill-withdrawal reflex

Habituation of the Aplysia gill-withdrawal reflex (and siphon-withdrawal reflex) has been attributed to low-frequency homosynaptic depression at central sensory-motor synapses. The recent demonstration that transfer of habituation between stimulation sites occurs in this model system has prompted the hypothesis that heterosynaptic inhibitory pathways also play a role in the mediation of habituation behavior. To test this hypothesis, the sites and mechanisms of neural plasticity which underlie transfer of habituation in Aplysia were examined. Transfer of habituation is a reduction in the reflex evoked at one stimulation site (siphon) due to repeated presentation of a stimulus to a second site (gill). Centrally mediated transfer of habituation, measured in a preparation lacking the siphon-gill peripheral nervous system (PNS), was associated with a reduced excitatory response in central motor neurons. Repeated tactile stimulation of the gill did not attenuate the gill response evoked by electrical stimulation of the branchial nerve nor the mechanoreceptor response recorded in LE sensory neurons. In contrast, repeated stimulation of siphon or gill at a site which was "off" the sensory field of a specific mechanoreceptor led to a diminution in synaptic transmission between that sensory neuron and its followers (motor neurons and inter-neurons). These data demonstrate that centrally mediated transfer of habituation results from heterosynaptic modulation of synaptic transmission at the sensory-motor (and sensory-interneuron) synapses. Therefore, habituation behavior in Aplysia is mediated through the conjoint action of homosynaptic and heterosynaptic inhibitory processes.     

Orienting reaction habituation in chronic alcoholics

A polygraphic study on resistance to habituation of the somatic (EMG), autonomic (finger plethysmogram, galvanic skin reaction, respiration) and EEG (acoustic-evoked potential and EEG-blocking reaction) components of the orienting reaction elicited by a repetitive auditory stimulus was performed in 67 chronic alcoholics and in 70 matched normal subjects (control group). The study showed a significantly lower resistance to habituation of the orienting reaction in alcoholics than in normal control subjects. The severity of this habituation disturbance depended on the patients' age, type of alcoholism, alcohol consumption intensity and chronicity, as well as the type of resting EEG.     

Electrophysiologic analysis of the process of recognizing target and non-target stimuli in healthy and oligophrenic children

In an automatized experiment, with a computer on line, amplitude-temporal parameters of evoked potentials (EPs) to purposive and non-purposive stimuli (digits), were analyzed in normal and mental retarded children. At unilateral stimuli presentation to the left or right visual half-fields EPs were recorded simultaneously in projection, TPO, parietal and central areas of the left and right hemispheres. It has been shown that in normal children, differential involvement of projection and associative structures in the analysis of sensory information takes place in both hemispheres. The amplitudes of most EP components in the range of 100-400 ms to the purposive stimuli are higher than to the non-purposive ones. Considerable similarity of EPs developing in response to ipsi- and contralateral stimulations of visual fields ("direct" and "transmitted" EP) is observed. In mental retarded children significant changes are revealed in intra- and interhemisphere organization of the process of perception of purposive and non-purposive stimuli. In the right hemisphere structures there are no differential EP reactions to the two types of stimuli. Significant, in comparison with the norm, prolongation of the latencies of most EP components is noted, especially in the structures of the left hemisphere, to the purposive stimuli. In the process of perception, changes are seen of the integration of functions of both hemispheres. The totality of disturbances of systemic brain organization at perceptive activity in mental retarded children may reflect neurophysiological mechanisms of mental deficiency.     

Persistent Postural-Perceptual Dizziness: A Matter of Higher,Central Dysfunction?

Objective

Persistent postural-perceptual dizziness (PPPD) is the most common vestibular disorder in the age group between 30 and 50 years. It is considered to be based on a multisensory maladjustment involving alterations of sensory response pattern including vestibular, visual and motion stimuli. Previous data supported a link between vestibular and pain mechanism. The aim of the study was to investigate whether other sensory inputs such as pain stimuli might be altered in terms of a more widespread central perception dysfunction in this disorder.

Methods

Nociceptive blink reflex was measured in 27 patients with PPPD and compared with 27 healthy, age and gender matched controls. The habituation of the R2 component of the blink reflex was evaluated as the percentage area-under-the curve (AUC) decrease in ten consecutive blocks of five averaged rectified responses. Additionally, clinical characteristics were evaluated.

Results

In patients with PPPD a lack of habituation was observed compared to healthy controls. Relative AUC decreased between the first and the tenth block by 19.48% in PPPD patients and by 31.63% (p = 0.035) in healthy controls. There was no correlation between clinical data (course of disease, comorbid depression, medication, trigger factors) or electrophysiological data (perception threshold, pain threshold, stimulus intensity) and habituation pattern. No trigeminal sensitization in terms of facilitation of absolute values could be detected.

Conclusion

Our study results supports the hypothesis of the multisensory dimension of impaired sensory processing in patients with PPPD extends beyond vestibular/visual motion stimuli and reflexive postural/oculomotor control mechanisms to other sensory inputs such as pain perception in terms of a more generalized disturbed habituation pattern.     

Genetic dispersion analysis of the relationship of epilepsy to anomalies in brain bioelectrical activity

Estimation of genetic and environmental components of phenotypical dispersion of paroxysmal and nonparoxysmal EEG abnormalities in epilepsy (118 probands and 179 relatives) in two phenotypical model frames has been obtained. The alternative phenotypical model was shown to be more adequate than quasicontinual for EEG abnormalities, and the part of additive genetic component (GA) comprises 15.7% for paroxysmal abnormalities and 49.4% for nonparoxysmal type. In the component type "belonging to one generation" joint influence of genetic and environmental factors on the process of forming EEG abnormalities in ontogeny was observed. The GA value for "epilepsy manifestation" symptom equal to 72.9% in general selection of probands increases to 97.4% in the subgroup of patients with nonparoxysmal abnormalities and 67.4% in the subgroup of patients with paroxysmal EEG abnormalities. It has been suggested that paroxysmal EEG abnormalities reflect their own epileptic process, and as far as nonparoxysmal abnormalities are concerned, they present phenotypical manifestation of the genetic system of predisposition to epilepsy.     

A comparison of the GHG emissions caused by manufacturing tissue paper from virgin pulp or recycled waste paper

Purpose

The aim of this work is to compare greenhouse gas (GHG) emissions from producing tissue paper from virgin pulp (VP) or recycled waste paper (RWP). In doing so, the study aims to inform decision makers at both company and national levels which are the main causes of emissions and to suggest the actions required to reduce pollution.

Methods

An attributional life cycle assessment (LCA) was performed in order to estimate and compare the GHG emissions of the two processes. LCA allows us to assess how the choice of raw material for VP and RWP processes influences total GHG emissions of tissue paper production, what are the main drivers behind these emissions and how do the direct materials; energy requirements and transportation contribute to the generation of emissions. The cradle-to-gate approach is carried out.

Results and discussion

The results show that demands for both thermal energy and electricity are higher for the RWP than for the VP if only the manufacturing stages are considered. However, a different picture emerges when the analysis looks at the entire life cycle of the production. GHG from the VP are about 30 % higher than the RWP, over the life cycle emitting 568 kg CO₂ eq more per kilogram of tissue paper. GHG emissions from the wood pulping alone were 559 g CO₂ eq per kilogram of tissue paper, three times higher than waste paper collection and transportation.

Conclusions

In terms of GHG emissions from cradle to gate, the recycled process less intensive than the virgin one for two reasons. First, as shown in the results the total GHG emissions from RWP are lower than those from VP due to relatively lower energy and material requirements. Second is the non-recyclability nature of tissue paper. Because the tissue paper is the last use of fibre, using RWP as an input would be preferable over using VP. The environmental profile of the tissue products both from RWP and VP can be improved if the following conditions are considered by the company. First, the company should consider implementing a cogeneration unit to simultaneously generate both useful heat and electricity. Second, it may consider changing the VP mix, in order to avoid the emissions associated with long distance transpiration effort. Third, there is the option of using sludge as fuel, which would reduce the total fossil fuel requirement.     

Time-frequency analysis of chemosensory event-related potentials to characterize the cortical representation of odors in humans

Background

The recording of olfactory and trigeminal chemosensory event-related potentials (ERPs) has been proposed as an objective and non-invasive technique to study the cortical processing of odors in humans. Until now, the responses have been characterized mainly using across-trial averaging in the time domain. Unfortunately, chemosensory ERPs, in particular, olfactory ERPs, exhibit a relatively low signal-to-noise ratio. Hence, although the technique is increasingly used in basic research as well as in clinical practice to evaluate people suffering from olfactory disorders, its current clinical relevance remains very limited. Here, we used a time-frequency analysis based on the wavelet transform to reveal EEG responses that are not strictly phase-locked to onset of the chemosensory stimulus. We hypothesized that this approach would significantly enhance the signal-to-noise ratio of the EEG responses to chemosensory stimulation because, as compared to conventional time-domain averaging, (1) it is less sensitive to temporal jitter and (2) it can reveal non phase-locked EEG responses such as event-related synchronization and desynchronization.

Methodology/Principal Findings

EEG responses to selective trigeminal and olfactory stimulation were recorded in 11 normosmic subjects. A Morlet wavelet was used to characterize the elicited responses in the time-frequency domain. We found that this approach markedly improved the signal-to-noise ratio of the obtained EEG responses, in particular, following olfactory stimulation. Furthermore, the approach allowed characterizing non phase-locked components that could not be identified using conventional time-domain averaging.

Conclusion/Significance

By providing a more robust and complete view of how odors are represented in the human brain, our approach could constitute the basis for a robust tool to study olfaction, both for basic research and clinicians.     

Disease specific characteristics of fetal epigenetic markers for non-invasive prenatal testing of trisomy 21

Background

Non-invasive prenatal testing of trisomy 21 (T21) is being actively investigated using fetal-specific epigenetic markers (EPs) that are present in maternal plasma. Recently, 12 EPs on chromosome 21 were identified based on tissue-specific epigenetic characteristics between placenta and blood, and demonstrated excellent clinical performance in the non-invasive detection of fetal T21. However, the disease-specific epigenetic characteristics of the EPs have not been established. Therefore, we validated the disease-specific epigenetic characteristics of these EPs for use in non-invasive detection of fetal T21.

Methods

We performed a high-resolution tiling array analysis of human chromosome 21 using a methyl-CpG binding domain-based protein (MBD) method with whole blood samples from non-pregnant normal women, whole blood samples from pregnant normal women, placenta samples of normal fetuses, and placenta samples of T21 fetuses. Tiling array results were validated by bisulfite direct sequencing and qPCR.

Results

Among 12 EPs, only four EPs were confirmed to be hypermethylated in normal placenta and hypomethylated in blood. One of these four showed a severe discrepancy in the methylation patterns of T21 placenta samples, and another was located within a region of copy number variations. Thus, two EPs were confirmed to be potential fetal-specific markers based on their disease-specific epigenetic characteristics. The array results of these EPs were consisted with the results obtained by bisulfite direct sequencing and qPCR. Moreover, the two EPs were detected in maternal plasma.

Conclusions

We validated that two EPs have the potential to be fetal-specific EPs which is consistent with their disease-specific epigenetic characteristics. The findings of this study suggest that disease-specific epigenetic characteristics should be considered in the development of fetal-specific EPs for non-invasive prenatal testing of T21.     

Evoked potentials of the visual center in lower vertebrates: Genesis and relation to unit activity

The origin and functional role of evoked potentials (EPs) of the tectum mesencephali (TM) were investigated in lower vertebrates, especially the frogRana temporaria L. EPs of TM were shown to reflect the synchronous appearance of postsynaptic potentials of the "first order." The fundamental characteristics of the EPs are determined by temporal dispersion of the afferent volley and localization of the afferent endings. The EPs play the role of a trigger for unit discharges, but the dynamics of intracentral excitatory activity is reflected only very slightly in EPs.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 5, pp. 515–519, September–October, 1970.     

Peculiarities of disorders of brain bioelectrical activity spatial-time organization in patients with different consciousness depression after severe head injury

Specific changes of bioelectrical brain activity was found in 27 patients with different level of posttraumatic consciousness depression by the methods of crosscorrelation, coherence and factor analysis of EEG. The changes of activity of morphofunctional systems of intracerebral integrations were revealed partially by decreasing of unspecific activity from brainstem structures reflected with increasing of slow wave activity and decreasing of EEG coherence in alpha- and beta-range. Depression of system organization of interconnections of bioelectrical brain activity in frontal and occipital regions of both hemispheres was also detected, and testified about decreasing of intercortical and thalamocortical brain system action under brain dislocation. The changes of integrative brain system activity, provides interhemispheric interaction, had the specific characted. Our results propose a "facilitation" of activity of system, providing "direct" interhemispheric connections through corpus callosum and other commissural tracts of telencephalon as a sequel of mesodiencephalon structures depression with steady reciprocal, antiphase relations of slow weve activity in symmetrical areas of hemispheres in coma II patients. The data of our research had shown no complete disintegration of system brain activity in coma II patients in spite of consciousness and brainstem reflexes depression.