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At least 235 records · Page 13Linked to original sources

PubMed2003

Chaotic analysis approach in neonatal magneto-encephalography.

The aim of this study was to investigate the presence of any non-linearity in the magneto-encephalographic recordings (MEG) in neonates born to pre-eclamptic mothers in comparison with the ones born to mothers having uncomplicated pregnancies, in order to find out differences in the mechanisms underlying their brain waves. Our study population consisted of 40 term neonates who were delivered normally, without any clinical signs of brain damage. Thirty of them had a normal pregnancy and labour with normal Apgar scores, umbilical cord pH, and birth weight, while 10 neonates had suffered a pre-eclamptic pregnancy. The above analysis of the MEG in the neonatal pre-eclamptic brain showed a lower dimension complexity as compared with the normal neonatal brain and a lower first Lyapunov exponent which means lower information processing. The non-linear analysis of the MEG activities in neonates may offer important perspectives to understand significant features of their brain function.

Adolescent↗

PubMed1979

[Fiftieth anniversary of Hans Berger's publication of the electroencephalogram. His first records in 1924--1931 (author's transl)].

For the fiftieth anniversary of Berger's first EEG publication, some of his early recordings obtained between 1924 and 1931 are discussed and illustrated. Examples of his protocols from the Freiburg Berger Archives are reproduced. Three types of Berger's early investigations are described: (1) String-galvanometer recordings obtained between 1924 and 1926, mainly from trephined patients with cerebral diseases, which usually showed brain waves slowed to 6--8 per second; (2) Direct recordings from the cortex and white matter proving the cortical origin of the EEG in 1930; (3) Typical unpublished EEG recordings of epileptics and of petit-mal attacks obtained in 1930 and 1931. Berger's first six papers published between 1929 and 1933 described nearly all the main EEG findings of cerebral diseases and the EEG alterations of normals during attention, sleep, and narcosis, but they did not report on convulsive potentials in the EEGs of epileptics. Berger had, however, obtained excellent records of epileptic EEG features, here depicted in Figs. 4 through 7. These remained unpublished until 1933 and 1938, because Berger suspected that they contained artifacts caused by blinks and facial movements which he had recorded in his controls (Fig. 4). Only in 1933, after other authors had described large amplitudes of convulsive potentials in the cortex of animals, did Berger publish parts of the EEGs of a petit-mal attack and of focal attacks in progressive paresis. In 1938, Berger presented the EEG of the beginning of a petit-mal attack with large 3/s spikes and waves recorded in 1931 which were similar to those described by Gibbs and coworkers in 1935. In 1933 and 1938, Berger interpreted the abnormal brain potentials of epileptics as signs of a preconvulsive state of the forebrain and suggested that the periods of 3/s waves were cortical correlates of an epileptic absence.

Electroencephalography↗

PubMed2003

Are the electroencephalograms mainly rhythmic? Assessment of periodicity in wide-band time series.

To test the hypotheses that (i). electroencephalograms (EEGs) are largely made up of oscillations at many frequencies and (ii). that the peaks in the power spectra represent oscillations, we applied a new method, called the period specific average (PSA) to a wide sample of EEGs. Both hypotheses can be rejected. Although the principal peaks in the two spectra agree most of the time, quite often a peak in the power spectrum accompanies no periodicity peak and some periodicity peaks have no power spectral peak. The Fourier spectrum is not a reliable indication of rhythms. EEG samples from patients during waking, sleeping and seizure states, and volunteer healthy subjects doing cognitive tasks quite often show no significant rhythms, on an arbitrary, common sense definition. When clear rhythms are seen, they involve one or two, rarely up to four or five simultaneous non-harmonically related frequencies. Rhythms are special cases; most of the power spectrum most of the time is nonrhythmic. "Good" rhythms usually have quite narrow peaks, with frequency modulation of <5%, strengths of >2.5 up to >10 times the expectation from chance, and they often show fine structure by being quite local and brief. Most rhythms are quasisinusoidal but others are sharp-cornered recurrent events with <50% duty cycle. In the face of wide variability, we do not report any systematic differences in periodicity among EEGs from different parts of the brain or different brain states or species; it will take many more exemplars of each state, species or brain part to establish characteristic features. The PSA method may be the best so far proposed to demonstrate and quantify periodicity in wide-band time series with noise, but it has serious limitations. Discussion leads to the conclusion that it is time for a new paradigm or metaphor for brain waves.

Animals↗

PubMed2005

Neurofeedback with anxiety and affective disorders.

A robust body of neurophysiologic research is reviewed on functional brain abnormalities associated with depression, anxiety, and obsessive-compulsive disorder. A review of more recent research finds that pharmacologic treatment may not be as effective as previously believed. A more recent neuroscience technology, electroencephalographic (EEG) biofeedback (neurofeedback), seems to hold promise as a methodology for retraining abnormal brain wave patterns. It has been associated with minimal side effects and is less invasive than other methods for addressing biologic brain disorders. Literature is reviewed on the use of neurofeedback with anxiety disorders, including posttraumatic stress disorder and obsessive-compulsive disorder, and with depression. Case examples are provided.

Anxiety Disorders↗

PubMed1984

Neural substrates of two different rhythmical vibrissal movements in the rat.

Normal rats show two types of rhythmical vibrissal movement, one synchronized precisely with alpha waves (about 9 Hz) of the thalamocortical system, and the other often synchronized with theta waves (about 7 Hz) of the septohippocampal system. The alpha-synchronized vibrissal movements appear while the rat stands still with a slow respiratory pattern, and are of small amplitude (a fine tremor). The theta-synchronized vibrissal movements appear during exploratory sniffing behavior, and are of large amplitude. Thus, a group of facial motoneurons which constitute the final common pathway for vibrissal movement apparently receive input convergently from these two neural systems. In the present study, we observed the following: (1) the two types of movement rarely, if ever, appeared simultaneously and the same was true of the two brain wave patterns. Topographically, the predominant appearance of the alpha waves was in the frontal (sensorimotor) cortex, whereas that of the theta waves was in the occipital cortex and hippocampus. (2) Bilateral ablation of either the entire neocortex or just its anterior (but not posterior) half eliminated the vibrissal alpha-tremor movement while leaving vibrissal theta-sniffing movement normal. In anterior decorticate rats, the tremor movements started to recover by 1-4 months, and were abolished again by the removal of the remaining posterior cortex. (3) Lesions of the medial septum or the fornix eliminated hippocampal theta waves, but had no effect on vibrissal sniffing movement or alpha wave-vibrissal tremor. (4) Cerebellectomy and, to a lesser extent, pharmacological lesions of the inferior olive slowed, but did not block, alpha waves. In addition, vibrissal tremor movement became intermittent and less vigorous. The same manipulations, however, did not affect theta wave-vibrissal sniffing movement. (5) Harmaline (30 mg/kg, i.p.) did not induce alpha-tremor, which, in combination with the results with cerebellectomy and inferior olive lesions, indicates that alpha-tremor is generated by a neural mechanism that is different from that for harmaline-induced generalized tremor of 10 Hz. These findings confirmed that there exist two patterns of synchrony between vibrissal movement and rhythmical brain activity in the rat, i.e. alpha wave-vibrissal tremor movement and theta wave-vibrissal sniffing movement, and suggest that the two patterns reflect a rhythmical mode of functioning of two different neural systems, probably the thalamocortical and the septohippocampal system, respectively.

Animals↗

PubMed1979

A finite state model for meditation phenomena.

Various reports of brain wave synchrony during Transcendental Meditation have appeared in the literature and have been interpreted as indicating a heightened state of integration of brain function. We suggest that this observed synchrony rather than indicating a greater integration of brain function might be an artifact of parts of the brain acting like a finite state machine. The finite state model is developed, its properties derived and a test for the hypothesis is presented.

Cerebral Cortex↗

PubMed1994

Multiple +Gz exposures cause brain edema in rats.

The most serious effect of high sustained +Gz (head-to-foot inertial load) known to occur in pilots of high performance aircraft is +Gz-induced loss of consciousness (G-LOC), which may result in pilot incapacitation and subsequent loss of life. G-LOC is believed to occur due to a critical reduction in cerebral blood flow (CBF). Recently, using a small animal centrifuge (SAC), we showed that +Gz exposure causes global cerebral ischemia in a rodent animal model. Since ischemia, depending upon the severity and duration, has been associated with increased brain water content or edema, the present study was undertaken. Rats were exposed to six exposures of either +25 Gz (30 s each) or +10 Gz (2 min each) in the SAC at +20 Gz.s-1 G onset rate. The appearance of G-LOC was monitored by the flattening of the electroencephalography (EEG) brain wave recording. G-LOC was observed at 101 +/- 46 and 19.2 +/- 5 s during +10 and +25 Gz exposures, respectively. The brains from these animals were removed 15 min to 24 h after the +Gz exposure and analyzed for edema formation (increase in the percentage of tissue water), metabolites, and cerebral blood volume (CBV). A significant decrease in glucose and an increase in lactate concentration were observed during +Gz exposure. Edema formation was observed 15 min after six exposures of either +10 or +25 Gz. A slight but significant decrease in CBV was also observed in rats exposed to six +10 Gz exposures. Edema formation was transient and resolved within 24 h. We concluded that multiple exposures of either +25 Gz, short duration or +10 Gz, long duration, that resulted in G-LOC, can cause cytotoxic brain edema which probably results from tissue hyperosmolality due to metabolic changes and accumulation of lactate during ischemia.

Acceleration↗

PubMed1986

Genetic aspects of alcoholism.

The importance of genetic factors in alcoholism is supported by family, twin, and adoption studies. The four-fold increased risk for this disorder in adopted-away sons of alcoholics supports the need for studies attempting to identify biologic and genetic factors that influence the future risk for alcoholism. Some methodological issues inherent in the search for markers of a predisposition toward alcoholism are reviewed and the results of studies of children of alcoholics are presented. Two potentially important findings include the decreased intensity of reaction to alcohol challenges in these high-risk young men, and the possibility that they demonstrate small amplitudes of the P300 brain wave. Some clinical and research implications of these findings are discussed.

Alcoholism↗

PubMed1984

Paradoxical contributions of EEG during protracted dying.

Estimates of the potential for recovery from severe brain damage have become more accurate as EEG and imaging techniques evolve. When all modern electrical criteria for brain death are satisfied, useful recovery is probably impossible. Many patients who have no reasonable chance of returning to a cognitive, sapient, or useful state may be nurtured throughout a prolonged final illness primarily because of brain waves that fluctuate in the 2- to 5-microV range. The incidence of such protracted dying is unknown. We illustrate diffuse low-amplitude wave forms and regional fragments recorded from a 27-year-old woman maintained on a respirator for six months after loss of brain-stem reflexes. Considering the limited noise-signal ratio of modern equipment, popular EEG criteria for death may be prematurely rigid, prolonging death in tragic circumstances.

Brain Death↗

PubMed1976

Drugs and PGO waves in the lateral geniculate body of the curarized cat. II. PGO wave activity and brain 5-hydroxytryptamine.

Ponto-geniculo-occipital (PCO) waves induced either by the benzoquinolizine derivative, Ro 4-1284 (=PGO(CPA), were continuously recorded and counted in the lateral geniculate bodies of unanaesthetized immobilized cats as described in the preceding communication. The effect of various drugs interacting with central 5-hydroxytryptaminergic mechanisms on the density (number hr(-1) or number 0.5 hr(-1) of PGO waves was investigated. The density of PGO waves was dose-dependently decreased and the waves were eventually abolished by the precursors of 5-hydroxytryptamine (5-HT), L-tryptophan and 5-hydroxytryptophan. 5-HT itself, injected intracerebroventricularly, tended to diminish the density. Lysergic acid diethylamide (LSD) was an extremely potent depressor of PGO(1284) and PGO(PCPA); psilocybine was almost as potent as LSD, whereas higher doses of N,N-dimethyltryptamine, bufotenine and yohimbine were required for the reduction of PGO waves. A number of tricyclic antidepressants reduced the density of PGO waves, their order of potency corresponding to that reported for their inhibitory effect on the uptake of 5-HT; tertiary amines were more potent than secondary amines. Desipramine was more potent on PGO(PCPA) THAN ON PGO(1284). Two dibenzothiepine antipsychotics, methiothepin and octoclothepin, increased the density of PGO(1284) and PGO(PCPA) and also induced PGO waves in untreated cats; the evidence suggests that these two compounds antagonize the effect of endogenous 5-HT in the brain. These results confirm some earlier findings and augment the pharmacological pieces of evidence for the stron inhibitory influence of 5-HT neurones on the generation ofPGO waves.

Animals↗

PubMed1993

Neurocardiology. Brain mechanisms underlying fatal cardiac arrhythmias.

Chaos theory may have a widespread application in medicine, from the analysis of protein structure at one end of the spectrum to fetal monitoring and the measurement of aging on the other. This application is especially on firm ground in cardiology, where it is simple and precise for the experimenter, and a primer exists for the clinician. As just presented, the point-correlation-dimension analysis of heartbeat variability is able to characterize the patterns of low-dimensional chaos produced by the heartbeat generator, a mechanism that is a composite of the voltage-dependent, neurotransmitter-dependent, and circulation-dependent ionic conductances that are all located in the myocardium where the heartbeat is formed. Most importantly, this deterministic measure of heartbeat variability is able to predict imminent lethal arrhythmogenesis with an accuracy that the more familiar stochastic measures do not have. This may arise because the PD2 is sensitive to the net degrees of freedom of the heartbeat generator, which, under the influence of the nerves and the coronary circulation, can be shifted so the resulting dynamics cause the initiation of lethal arrhythmogenesis. Application of chaos theory in neurology may be equally fruitful because the deterministic measures can discriminate among neuronal firing patterns, reveal subtle changes in brain waves, and be related to higher cognitive processes. Psychiatry also seems quite likely to benefit more and more from the application because the algorithms can discriminate schizophrenic brain functions from normal ones. Thus it can be expected that future applications will enable observation of biologic processes all along the brain-heart axis by which lethal ventricular fibrillation is regulated and perhaps even caused by its determination of the heartbeat dynamics. The subfield of neurocardiology has come a long way since it was first positively identified as an important research area. It took a lot of experiments to show how lethal cardiac arrhythmogenesis is involved with cerebral activities delivered over autonomic pathways. Although we do not yet fully understand the causal mechanism of lethal arrhythmogenesis, we may be getting close. It will become increasingly imperative for the clinical neurologist, along with the cardiologist, to understand the importance of neurocardiology in medical therapy and for the neurologist, along with the cardiologist and psychiatrist, to understand its importance in preventive treatments.

Animals↗

PubMed2000

Right-posterior face processing anomaly in depression.

Evidence of a right-posterior brain anomaly was found in a study of 19 individuals with major depression and 15 controls. Participants performed a recognition-memory task involving positive, neutral, and negative face and word stimuli. Scalp brain wave topography suggested a region-specific anomaly in the depressed group. Individuals with major depression demonstrated a reduction in the N200 component of the event-related brain potential to faces and not words. Furthermore, results indicate that the regional anomaly is specific to positive facial stimuli. Findings are interpreted in light of a model of regional brain specialization in emotion and psychopathology.

Adult↗

PubMed1995

Magnetic and electric brain activity evoked by the processing of tone and vowel stimuli.

Sustained magnetic and electric brain waves may reflect linguistic processing when elicited by auditory speech stimuli. In the present study, only in the latency interval subsequent to the N1m/N1 has a sensitivity of brain responses to features of speech been demonstrated. We conclude this from studying the auditory-evoked magnetic field (AEF) and the corresponding evoked potential (AEP) in response to vowels and a tone. Brain activity was recorded from the left and the right hemisphere of 11 subjects. Three aspects of transient activity were examined: (1) the amplitudes and source characteristics of the N1m component of the AEF; (2) the amplitudes and source characteristics of the sustained field (SF), and (3) the corresponding amplitude characteristics of the AEP. Sustained potential amplitudes and SF root mean square amplitudes, as well as the dipole strength of the SF source, were found to be larger for vowel-evoked signals than for signals elicited by the tone stimulus. The amplitude and dipole strength effects had an interaction with hemisphere, with larger interhemispheric differences for the vowel condition, as well as larger tone-vowel differences of these parameters in the speech-dominant left hemisphere. No statistically significant hemisphere-by-stimulus-type interactions were found in N1/N1m amplitudes and N1m source parameters.

Adult↗

PubMed1986

Information processing deficits in anhedonia and perceptual aberration: a psychophysiological analysis.

Building on recent reports of psychophysiological deviance in two groups believed to be at risk for psychosis, the present study sought to identify corresponding cognitive deviance in these groups. Subjects defined according to Chapman's questionnaires on physical anhedonia (n = 16) and perceptual aberration (n = 16) were tested in an auditory discrimination task while brain wave and autonomic activity was monitored. Although the discrimination performance of at-risk subjects equaled that of controls (n = 16), significant group differences occurred in event-related brain potential and heart rate responses. Interpreted within an information processing model of the discrimination task, these results suggest a deficit in the use of memory templates by anhedonics, for which they can compensate if given adequate stimulus input.

Adolescent↗

PubMed1989

The effects of electrode placement upon EEG biofeedback training: the monopolar-bipolar controversy.

Roles of tradition, convenience, and noise or artifact rejection are discussed with regard to the monopolar versus bipolar electrode placement controversy in electroencephalography (EEG). Particular emphasis is placed on the relevance to biofeedback. The crucial interactions between the differential amplifier, brain waves, and monopolar/bipolar placements are discussed. Through logical analysis and empirical observation, it is demonstrated how the very nature of the EEG's differential amplifiers must destroy those elements of brain activity which are common to the recording electrodes. Controlled experiments further illustrate the critical importance of electrode placements. Various methods, including preferred electrode placements, are presented to help resolve recording problems that frequently arise. It is concluded that there are serious implications for researchers, EEG clinicians, biofeedback providers, and their clients in preferring one type of electrode placement technique over the other. EEG recording accuracy is affected by this choice.

Amplifiers, Electronic↗

PubMedDate not supplied

EEG slow waves and sleep spindles: windows on the sleeping brain.

Slow waves and sleep spindles are prominent features of the EEG in non-REM sleep and some of the neurophysiological mechanisms underlying their genesis have been elucidated. In humans, slow-wave activity in non-REM sleep increases and EEG activity in the frequency range of sleep spindles decreases when wakefulness prior to sleep is varied from 2 to 40 h. The opposite changes are observed in the course of sleep, even when sleep is scheduled out of phase with the circadian rhythm of sleep propensity. Within non-REM sleep episodes the association between slow waves and sleep spindles is bi-phasic: both activities are correlated positively at the beginning and end of non-REM sleep episodes whereas in the middle part of non-REM sleep episodes high values of slow-wave activity coincide with low levels of spindle activity. An extension of wakefulness enhances the rise rate of slow-wave and spindle activity at the onset of sleep. Since macroscopic slow waves and sleep spindles both are dependent on hyperpolarization and synchronization of neurons in thalamo-cortical and cortical circuits, the sleep deprivation induced changes in these EEG activities may be related to reduced activating input to thalamo-cortical and cortical neurons, local facilitation of their hyperpolarization or facilitation of their synchronization. The precise regulation of slow-wave and spindle activity as a function of the duration and intensity of prior sleep and wakefulness demonstrates that these EEG oscillations are accurate indicators of non-REM-sleep homeostasis and suggests that they are fundamental to the sleeping brain.

Animals↗

PubMed1992

Spontaneous phasic activity in the brain: differences between waves in lateral geniculate and central lateral nuclei across sleep states.

Ponto-geniculo-occipital (PGO) waves are spontaneously-occurring macropotential waveforms recorded in the pons, lateral geniculate body (LGB) and occipital cortex. PGO waves mark the onset and course of rapid eye movement sleep (REM). PGO-like waves can be recorded in several brain areas including the thalamic central lateral nucleus (CL). Alerting stimuli elicit PGO waves (PGOE) from LGB and waves from CL (CLE) in all behavioural states. We compared spontaneous activity in LGB and CL across behavioral states to examine the relationship of CL waves to PGO waves. Spontaneous waves in LGB and CL may occur concurrently or separately in all states. Although REM is marked by a high level of LGB PGO activity, CL waves are rare. Frequencies of CL and LGB waves are similar in non-REM (NREM) although the waves do not necessarily occur at the same time. These findings suggest that the widespread phasic activity recorded throughout the brain in sleep cannot be assumed to be a non-specific unitary phenomenon propagated from a single brainstem generator.

Journal Article↗

PubMed2003

Neural basis of rhythmic timing networks in the human brain.

The study of rhythmicity provides insights into the understanding of temporal coding of music and temporal information processing in the human brain. Auditory rhythms rapidly entrain motor responses into stable steady synchronization states below and above conscious perception thresholds. Studying the neural dynamics of entrainment by measuring brain wave responses (MEG) we found nonlinear scaling of M100 amplitudes generated in primary auditory cortex relative to changes in the period of the rhythmic interval during subliminal and supraliminal tempo modulations. In recent brain imaging studies we have described the neural networks involved in motor synchronization to auditory rhythm. Activated regions include primary sensorimotor and cingulate areas, bilateral opercular premotor areas, bilateral SII, ventral prefrontal cortex, and, subcortically, anterior insula, putamen, and thalamus. Within the cerebellum, vermal regions and anterior hemispheres ipsilateral to the movement became significantly activated. Tracking temporal modulations additionally activated predominantly right prefrontal, anterior cingulate, and intraparietal regions as well as posterior cerebellar hemispheres. Furthermore, strong evidence exists for the substantial benefits of rhythmic stimuli in rehabilitation training with motor disorders.

Auditory Perception↗