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Results for “Brain waves”

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At least 937 records · Page 52Linked to original sources

PubMed1999

Brain stem auditory evoked potentials in the human fetus during labor.

OBJECTIVE: The aim of this study was to record, during labor, the brain stem auditory evoked potentials of the fetus from standard fetal scalp electrodes. STUDY DESIGN: A personal computer-based instrument was developed to record, during labor, brain stem auditory evoked potentials from 10 fetuses ranging in gestational age from 36 to >/=40 weeks. Auditory stimulus was provided by clicks (16/s) delivered on the mother's abdomen with an intensity of 120 dB. The evoked potential signals were digitized and averaged. Interfering artifacts were excluded from the averages. RESULTS: In 80% of the subjects, all the principal waveforms of the brain stem auditory evoked potentials-waves I, III, and V-were clearly identifiable. The latency for wave I ranged from 1.2 to 2.2 ms, wave III from 3.4 to 5.6 ms, and wave V from 5.8 to 8.4 ms. The morphologic features of the waveform and the interwave latency values were similar to those of normal term infants recorded in the past studies. CONCLUSION: We have reestablished that it is possible to record auditory evoked potentials during labor from fetal scalp electrodes. Brain stem auditory evoked potentials may be a useful screening tool for at least the severely neurologically damaged fetus.

Electrodes↗

PubMedDate not supplied

The human fetal auditory evoked potential.

The brain-stem auditory evoked potential (BAEP), a sensitive test of the functional status of the neonatal brain, has not been studied in utero since no practical technique for human fetal recording is available. We have developed a simple recording technique which allows continuous monitoring of the fetal AEP during labor. Waves I, III and V of the fetal brain-stem AEP have been consistently identified. Wave form morphology, interpeak latencies, and latency-intensity relations are similar to postnatal recordings. Middle latency potentials have also been recorded, with wave forms that correspond to the neonatal middle latency AEP.

Brain Stem↗

PubMed2006

[Changes in electroencephalograph and somatosensory evoked potential and their relationship with neuron apoptosis in rat after ischemic insult to brain].

OBJECTIVE: To study the changes in electroencephalograph (EEG) and somatosensory evoked potential (SEP) and their relationship with neuron apoptosis in rat after ischemic insult to the brain. METHODS: Thirty-five SD rats were randomly divided into normal, sham operated and 3, 12, 24, 48, 72 hours after ischemia/reperfusion (I/R) groups with 5 rats in each group. The ischemia of brain was produced by clamping 4 vessels to the brain for various periods of time. Changes in EEG and SEP were recorded at different time after I/R, and the amounts of apoptotic neurons in hippocampus and cortex after I/R were assessed with terminal deoxynucleotidyl transferase mediated dUTP biotin nick end labeling (TUNEL) and acridine orange ethidium bromide (AO/EB) fluorescence examination techniques. RESULTS: Compared with sham operated group, EEG amplitude decreased significantly (all P<0.05), and the proportion of Delta wave increased significantly after ischemia of the brain (all P<0.05). The latent period of P1 wave crest extended markedly (all P<0.05), and P1-N1 amplitude decreased significantly after I/R (all P<0.05). EEG and SEP changes were correlated with the apoptosis and loss of neurons, which started in the hippocampus and extended to frontal cortex and parietal cortex. CONCLUSION: The combined analysis of EEG and SEP can reflect the process of neuron apoptosis, which is helpful for the diagnosis and evaluation of prognosis of patients suffering from cerebral ischemia.

Animals↗

PubMed1988

[EEG changes in early summer meningoencephalitis].

The nature and extent of EEG changes in 114 patients with tick-borne encephalitis were reported. The diagnosis was confirmed by the clinical picture, as well as the pathological increase in cells in the liquor and serologically by positive Ig-M titres. EEG findings were compared in patients with or without involvement of the brain. The EEG revealed pathological results in 76 patients, whereby the dominant pathological change was frequently occurring synchronous bursts of generalized slow bilateral waves. 12 patients with involvement of the brain all showed pathological EEG changes, a much higher rate than in the remaining patients and these findings were also more marked. However, 64 patients with clinical evidence of meningitic involvement showed pathological EEG changes, too.

Adolescent↗

PubMedDate not supplied

Enhancement of the amplitude of somatosensory evoked potentials following magnetic pulse stimulation of the human brain.

In this study we have demonstrated an enhancement of cortically generated wave forms of the somatosensory evoked potential (SEP) following magnetic pulse stimulation of the human brain. Subcortically generated activity was unaltered. The enhancement of SEP amplitude was greatest when the median nerve was stimulated 30-70 msec following magnetic pulse stimulation over the contralateral parietal scalp. We posit that the enhancement of the SEP is the result of synchronization of pyramidal cells in the sensorimotor cortex resulting from the magnetic pulse.

Brain↗

PubMed2006

Frequency domain near-infrared spectroscopy technique in the assessment of brain oxygenation: a validation study in live subjects and cadavers.

BACKGROUND: Studies with continuous wave near infrared spectroscopy (CW-NIRS) have shown little difference in brain oxygenation of dead compared to live subjects. We determined brain oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations in healthy volunteers and cadavers using frequency domain near infrared spectroscopy (FD-NIRS). METHODS: Regional OHb and HHb, brain oxygen saturation (SO2), and total hemoglobin (tHb) were determined. Nine patients who died in the hospital were evaluated by FD-NIRS in the morgue 7-96 h after death was confirmed. Ten volunteers served as a control group. RESULTS: Absolute concentrations of brain tissue OHb and HHb were 24.9 +/- 9.1 uM and 13.8 +/- 32 uM, respectively, in live subjects. In dead subjects, OHb was 1.3 +/- 2.1 uM and HHb was 30.8 +/- 14.4 uM (both P < 0.05 compared to live). OHb showed a 90% decrease within 7h of death. There was a significant trend for a continued decrease in OHb from 7 to 96 h. CONCLUSION: OHb decreased and HHb increased in dead patients compared to live volunteers. Depletion of OHb primarily occurred within 7 h of death but continued gradually over 96 h. FD-NIRS was a novel technique for determining OHb and HHb changes following death.

Adult↗

PubMed1989

[Changes in the spreading depression wave in rats in the postresuscitation period].

Functional state of the rat brain cortex after a 10-minute arrest of blood circulation was studied by means of the spreading depression wave, the latter leading to significant energy expenditures and being accompanied by a transmitter output and changes in extra- and intracellular ion concentration. The changes in the spreading depression wave took place at different stages of the postresuscitation period (2 hours to 2 1/2 months), suggesting various pathological changes in functional state of the brain cortex induced by disturbances in neurological interrelationships.

Animals↗

PubMed1995

Experimental missile wounding of the brain.

If a missile penetrates a cerebral hemisphere and does not severely disrupt the brain or transit a vital brain structure, it is hypothesized that the indirect effect of ordinary pressure waves set up by the interaction of missile and tissue and that impinge on brain stem respiratory nuclei determines life or death. The likelihood of fatal apnea is a direct function of missile energy of deposit within the brain. With brain wounding, a reduction in CO may also occur, but missile energy required to produce a significant CO decrease is in excess of that required to produce respiratory problems. Unless the individual managed to survive a period of apnea or respiratory resuscitation occurred, the effects of apnea would overshadow any CO decreases. Although transmitted ordinary pressure waves might interfere with the reticular activating system within the brain stem and produce persistent coma, specific long-lasting neurologic defects from a missile wound usually result from direct missile damage to the cerebral cortex or cortical projections. In designing treatments for missile wounds of the brain, two distinct entities must be kept in mind: the brain stem and the cerebral cortex. To decrease the immediate mortality from brain wounding, prompt treatment has to be devised to aid dysfunctional respiratory nuclei and possibly cardiac control nuclei. To decrease long-term neurologic morbidity, drug therapy has to be instituted to help injured cerebral cortical neurons for days to weeks after wounding. Totally different strategies and drugs may be needed to treat the brain stem as opposed to the cerebral cortex.

Animals↗

PubMedDate not supplied

Study into penetration speed during laser cutting of brain tissues.

The applications of CO2 continuous-wave lasers in neurosurgery have become important in recent years. Theoretical considerations of laser applicability in medicine are subsequently confirmed experimentally. To obtain precision operation in the laser cutting process, further theoretical developments and experimental studies need to be conducted. Consequently, in the present study, the heat transfer mechanism taking place during laser-tissue interaction is introduced using Fourier theory. The results obtained from the theoretical model are compared with the experimental results. In connection with this, an experiment is designed to measure the penetration speed during the laser cutting process. The measurement is carried out using an optical method. It is found that both results for the penetration speed obtained from the theory and experiment are in a good agreement.

Absorption↗

PubMed2005

Instantaneous acceleration and amplification of hippocampal theta wave coincident with phasic pontine activities during REM sleep.

Rapid eye movement (REM) sleep is characterized by hippocampal theta waves and phasic spike-like waves originating from the pons, termed ponto-geniculo-occipital (PGO) waves in cats and pontine (P) waves in rats. While the theta wave and PGO/P wave have been suggested to participate in higher-order brain functions, their generation mechanisms and roles in brain functions have been studied independently. Therefore, the present study investigated instantaneous aspects of the relationship between theta waves and PGO/P waves in both cats and rats. Theta wave was instantaneously accelerated several hundred milliseconds before the negative peak of the PGO/P wave in both animals, and was also amplified just before PGO/P wave occurrence. Considering the integrated knowledge provided by studies of both animals, these results suggest that PGO/P wave-related activities in the pons are delivered to the theta wave generator. The activations of the theta wave coincident with PGO/P wave might facilitate cooperative contribution to higher-order brain functions in REM sleep.

Action Potentials↗

PubMed2003

Source distribution of neuromagnetic slow-wave activity in schizophrenic patients--effects of activation.

When slow waves in the EEG delta and theta frequency range appear in the waking state, they may indicate pathological conditions including psychopathology. The generators of focal slow waves can be mapped using magnetic source imaging. The resulting brain maps may possibly characterize dysfunctional brain areas. The present study examined the stability of the density and distribution of MEG slow waves during three conditions-rest, mental arithmetic and imagery-in 30 schizophrenic patients and 17 healthy controls. Schizophrenic patients displayed a higher density of delta and theta generators primarily in temporal and parietal areas. The group difference was not affected by the particular conditions. The focal concentration of delta and theta slow waves did not differ between patients with and without neuroleptic medication, whereas the prominence of theta dipoles in the temporal area correlated with neuroleptic dosage. The relative amount of temporal slow waves was correlated with the negative symptoms score (PANSS-N) suggesting that temporal dysfunction may be related to negative symptomatology.Results suggest that the distribution of slow-wave activity, measured in a standardized setting, might add diagnostic information about brain abnormalities in schizophrenia.

Adult↗

PubMed1983

Auditory evoked potentials recorded from the cochlear nucleus and its vicinity in man.

Intracranial responses from the auditory nerve and the cochlear nucleus were recorded from patients undergoing neurosurgical operations during which these structures were exposed. Responses to stimulation of the ipsilateral ear with short tonebursts from the vicinity of the cochlear nucleus show a large surface-negative peak, the latency of which is close to that of peak III in the auditory brain-stem evoked potentials recorded from scalp electrodes. There was also a response to contralateral stimulation, smaller in amplitude and with a longer latency. It is concluded that the cochlear nucleus is the main generator of peak III responses, and that structures of the ascending auditory pathway that are more central than the cochlear nucleus are unlikely to contribute to wave III of the auditory brain-stem evoked potentials.

Brain Stem↗

PubMed1996

Nucleus basalis magnocellularis and pedunculopontine tegmental nucleus: control of the slow EEG waves in rats.

Certain human disorders, which are characterized by learning and memory disturbances, are also accompanied by synchronizations of the cortical electroencephalogram (EEG). Although the EEG synchronization was casually related to the degeneration of the cholinergic basal forebrain, degenerations were found also in the cholinergic pontomesencephalic tegmentum. The present study was carried out to prove whether lesions of rat's pedunculopontine tegmental nucleus (PPTg) may cause EEG synchronizations like lesions of the basal forebrain. The effects of the unilateral ibotenic acid lesions of the nucleus basalis magnocellularis (NBM) and of the PPTg on the frontal and occipital EEG were compared in different behavioural states. The NBM lesion caused unilateral spectral power increases of all frequencies up to 20 Hz in the frontal EEG that were stronger with increased arousal level. Additionally, synchronized spike and wave discharges appeared in the frontal EEG. The NBM may suppress especially the delta EEG waves in the frontal motor cortex during motor active behaviours. The PPTg lesion caused unilateral suppressions of the occipital theta rhythm during exploratoring sniffing. During grooming the power of the frontal delta waves were elevated. Furthermore, the PPTg lesion caused a suppression of slow sleep waves. The results may indicate that a degeneration of both brain regions may change differently the power of the cortical slow EEG waves.

Acetylcholinesterase↗

PubMed1999

[Lissencephaly type I: electroencephalographic findings and neuroradiological classification].

Lissencephaly type I is a diffuse type of migration disorder that contains agyria and/or pachygyria on the brain surface. We experienced 5 cases of this disease and evaluated their electroencephalographic findings and seizure types based on the neuroradiological classification of lissencephaly. Ages at seizure onset ranged from 2 months to 4 months (mean 3.2 months). The patients with complete agyria had generalized tonic seizures, and those with pachygyria partial seizures or tonic spasms. The characteristic findings of complete agyria in electroencephalogram were high-voltage alfa activity. The amount of high-voltage slow waves increased with the ratio of pachygyria on the brain surface. The appearance of multifocal spikes and sharp waves suggested irregular arrangement of pachygyria on the brain surface.

Brain↗

PubMed2002

Abrupt onset of sensorineural hearing loss and tinnitus in a patient with capillary telangiectasia of the pons.

Capillary telangiectasia is often found incidentally on magnetic resonance imaging and may be associated with minor neurologic symptoms, but there has been little evidence about whether such lesions are responsible for these symptoms. Here we report a case of capillary telangiectasia of the right mid pons, which was associated with the abrupt onset of tinnitus and sensorineural hearing loss. Examination of the auditory brain stem responses showed abnormalities of waves III and IV on the left and bilateral prolongation of the interwave intervals. Optokinetic nystagmus showed slight left-right asymmetry.

Adult↗

PubMed1987

Functional and metabolic correlates of long series of cortical spreading depression waves in rats.

Repetitive generation of spreading depression (SD) waves may induce metabolic and functional disturbances in the invaded brain regions. In order to better characterize this state, up to 60 SD waves were elicited in the cerebral cortex of anesthetized rats by intracortical injections of 2 microliters of isotonic K-acetate repeated at regular 5-min intervals. Propagation rate of SD between capillary electrodes located 1 mm and 7 mm from the injection site gradually decreased and after 35-45 waves became irregular. In another series of experiments SD-induced changes of cyclic adenosine monophosphate (cAMP) level were examined after 24 SD waves. Although no irregularities of SD propagation were observed, maximum level of cAMP in the SD-invaded cortex decreased from 270% in controls to 170% after 24 waves. Also, the recovery of the nucleotide was slowed down. Metabolic alterations thus preceded irregularities in SD propagation.

Acetates↗

PubMed1998

Refractory properties of auditory brain-stem responses evoked by electrical stimulation of human cochlear nucleus: evidence of neural generators.

In this study of electrically-evoked auditory brain-stem responses (EABRs) elicited by cochlear nucleus stimulation, 3 waves were identified after the initial wave that is directly initiated by the electric stimulus. Varying the rate of periodic stimulation or the interval between pairs of stimuli revealed that the shorter the latency of a wave, the faster it recovered from activation (i.e. shorter refractory period). The slow recovery of the third wave and an accompanying contribution to the second wave could be accounted for by postsynaptic generation in the two medial superior olivary nuclei (MSO); the faster recovery of another contribution to the second wave by generation in an axonal tract bending around the contralateral MSO; and the fastest recovery of the first wave by another axonal pathway having larger axons. Comparison with the relative latencies and spatial distribution of an acoustically-evoked auditory brain-stem response (AABR) indicated that the third wave corresponds to wave V, the second to wave IV (called IVb), and the first to a wave that precedes wave IV (called IVa). The anatomical interpretations for the two later waves of the EABR are consistent with most of the extant data on the neural generators of AABR waves IV and V. Thus, the present data and analysis strengthen the identification of the electrically evoked responses as EABRs and provide a firmer foundation for intra-operative EABR monitoring to assist auditory brain-stem implant placement.

Brain Stem↗

PubMed1991

[The reflection of functional differences between the hemispheres in the form of the EEG waves].

The EEG was recorded in 3 symmetrical sites of the human brain with subsequent calculation of the parameter of mean level of asymmetry (MLA) in the EEG wave fronts. The MLAs were shown to change after functional loads of visual-spatial and verbal-logical types. The MLA seems to be an informative parameter of qualitative specifics of neural processes in the left and right hemispheres.

Adolescent↗