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At least 199 records · Page 11Linked to original sources
PubMed2001

Fractal probability measures of learning.

Herein we introduce a technique for determining the fractal dimension of time series obtained from complex systems, in particular brain-wave data in which the fractal dimension is arguably a measure of awareness and learning. The technique is based on determining the probability distribution for the degree of irregularity in random time series and has been shown to be superior in terms of efficiency and reliability to more commonly used methods that rely on the correlation function. We speculate that the scaling behavior of the probability measure is an indicator of an allometric relation between learning and brain-wave activity.

Algorithms↗
PubMed1998

Imaging spreading depression and associated intracellular calcium waves in brain slices.

Spreading depression (SD) was analyzed in hippocampal and neocortical brain slices by imaging intrinsic optical signals in combination with either simultaneous electrophysiological recordings or imaging of intracellular calcium dynamics. The goal was to determine the roles of intracellular calcium (Ca2+int) waves in the generation and propagation of SD. Imaging of intrinsic optical signals in the hippocampus showed that ouabain consistently induced SD, which characteristically started in the CA1 region, propagated at 15-35 micrometer/sec, and traversed across the hippocampal fissure to the dentate gyrus. In the dendritic regions of both CA1 and the dentate gyrus, SD caused a transient increase in light transmittance, characterized by both a rapid onset and a rapid recovery. In contrast, in the cell body regions the transmittance increase was prolonged. Simultaneous imaging of intracellular calcium and intrinsic optical signals revealed that a slow Ca2+int increase preceded any change in transmittance. Additionally, a wave of increased Ca2+int typically propagated many seconds ahead of the change in transmittance. These calcium increases were also observed in individual astrocytes injected with calcium orange, indicating that Ca2+int waves were normally associated with SD. However, when hippocampal slices were incubated in calcium-free/EGTA external solutions, SD was still observed, although Ca2+int waves were completely abolished. Under these conditions SD had a comparable peak increase in transmittance but a slower onset and a faster recovery. These results demonstrate that although there are calcium dynamics associated with SD, these increases are not necessary for the initiation or propagation of spreading depression.

Animals↗
PubMed1994

Prospective controlled studies of the behavioral and biological effects of exogenous corticosteroids.

The brain is an important target organ for both endogenous and synthetic corticosteroid hormones, but the nature of steroid action there is complex. We review a series of studies that was designed to elucidate possible relationships between the behavioral and biological effects of exogenous corticosteroids. In these studies, corticosteroids were administered to intact animals or to currently healthy volunteers, and behavioral and biological indices of corticosteroid effects were jointly assessed. In the first study, chronic corticosterone administration to intact rats resulted in increased locomotor activity (consistent with increased caudate or nucleus accumbens dopamine activity) and increased caudate homovanillic acid (HVA) levels. In the second study, acute dexamethasone administration to healthy human volunteers resulted in increased plasma HVA levels. These findings in animals and humans may help explain vulnerability factors for experiencing psychotic reactions during chronic corticosteroid treatment. To more closely mimic clinical conditions in which "steroid psychoses" develop, we administered a higher dose and more chronic corticosteroid medication (prednisone, 80 mg/day for 5 days) in a double-blind manner to healthy volunteers. Consistent with prior clinical observations, behavioral changes were variable across subjects. Seventy-five percent of the individual volunteers developed mild behavioral side effects during prednisone administration; in addition, significant, specific deterioration in cognitive performance was observed. Prednisone administration was also associated with significant decreases in plasma levels of adrenocorticotropic hormone (ACTH), cortisol, and 3-methoxy,4-hydroxyphenyl glycol (MHPG) and in cerebrospinal fluid (CSF) levels of ACTH, beta-endorphin (BE), beta-lipotropin (BLPH), somatostatin-like immunoreactivity (SLI), and norepinephrine (NE). It was also associated with significant slowing of brain wave electrical activity (viz., an increase in theta wave activity) on quantitative electroencephalography. Several behavioral changes, particularly those relating to mood or cognition, were related to changes in CSF levels of NE, MHPG, ACTH, BE, BLPH, and SLI and to the slowing of brain wave activity. Our preliminary data raise the possibility that the behavioral effects of exogenous corticosteroids have specific neural concomitants and that the pattern of biological changes produced contributes to the behavioral variability observed. Steroid effects on levels of biogenic amines, pro-opiomelanocortin (POMC)-related peptides and somatostatin, among others, as well as on brain electrophysiology, may be behaviorally relevant and are highlighted as being worthy of further investigation.

Adrenal Cortex Hormones↗
PubMed1990

[A simplified method for evaluation of brain function--basic and clinical study on electroencephalogram by the nasopharyngeal lead].

In making a decision for death, it is well said that brain stem electroencephalogram (EEG) could be an important index. We applied Ishida's nasopharyngeal lead to animals (canine), normal healthy men and patients with brain dysfunction. In normal healthy men, the nasopharyngeal lead revealed clear brain waves. Additionally, we tried a photic stimulation in all the models and a gradual removal of the cerebrum in canines to investigate whether interaction between Ishida's nasopharyngeal lead and the cortical electroencephalogram exists. Furthermore, whenever there was a chance, we examined instances with brain dysfunction by the method, and confirmed that brain waves obtained from Ishida's nasopharyngeal lead were derived from the skull base.

Adult↗
PubMed1996

Sources of spontaneous slow waves associated with brain lesions, localized by using the MEG.

Electric or magnetic slow wave brain activity can be associated with brain lesions. For an accurate source localization we transformed the magnetoencephalographic (MEG) coordinate system to the magnetic resonance imaging (MRI) system by using a surface fit of the digitally measured head surface and the reconstructed surface of the MRI scan. Furthermore we solved the problem to separate sources of focal activity from other multiple sources by introducing a spatial average, the Dipole Density Plot (DDP). The DDP shows in a quantified manner concentrations of dipoles across time. The DDP uses the single dipole model adequately, because only those signal sections will be analyzed, where one component contributes to the signal predominantly. In all cases, where multiple sources concurrently active are to be localized, a current distribution analysis will be used, the Current Localization by Spatial Filtering (CLSF). All source localization procedures were tested using structural brain lesions, which were verified by imaging techniques (MRI or CT), showing the results in close topographical relation to the lesions. The results so far let us assume, that the DDP and the CLSF are valuable tools to localize sources of focal spontaneous slow wave electrical brain activity.

Brain↗
PubMed2000

Sleep, memory maintenance, and mental disorders.

Memory circuits of the brain are activated by self-generated brain waves, primarily during sleep. These activations refresh the efficacies (strengths) of synapses in affected circuits, maintaining the efficacies at the "dedicated" values that support circuit functions. The neural pathologies underlying many mental disorders appear to exert their deleterious influences by inducing abnormalities in brain waves. The abnormal waves, in turn, fail to sustain dedicated synaptic efficacies in memory circuits, leading to mental malfunction. Dreaming is an "unconscious" awareness of circuit reinforcement during sleep, with dream contents being derived from the activated circuits. When synaptic efficacies are degraded, the dreams are illusory.

Humans↗
PubMed1983

Biofeedback: a possible substitute for smoking, experiment I.

Biofeedback techniques were utilized in this study to identify those physiological variables which possibly contribute to maintenance of cigarette smoking and to investigate the hypothesis that smoking frequency would decrease when individuals were trained via biofeedback procedures to increase 8-12 Hz occipital EEG activity as a substitute for smoking. Results of the study indicate that of the six smokers physiologically monitored, the following physiological changes occurred while actually smoking one cigarette: four smokers increased the percent of time they were producing 4-8 cycle per second (Hz) brain waves; five smokers increased their heart rate (beats per minute); all six smokers decreased their 8-12 Hz activity. Immediately after the smoking of one cigarette, six of the smokers demonstrated an increase in their heart rate and four of the smokers demonstrated a decrease in their skin temperature. There did not appear to be any specific consistent brain wave change across the subjects. Two smokers, who were able to continue producing high levels of 8-12 Hz activity without use of the biofeedback equipment, were able to quit completely at the end of an eight-month followup period.

Alpha Rhythm↗
PubMed1988

Genetic determination of the human EEG. Survey of recent results on twins reared together and apart.

In this article, we have discussed recent progress in quantifying the genetically determined component of the resting EEG. This progress has been made possible in particular by the application of advanced information processing techniques such as "supervised learning," and the development of a problem-oriented "similarity" concept. Our work aimed at modeling previous findings regarding the distinct individuality of human brain-wave patterns, the high similarity between the EEGs of monozygotic twins, and the average within-pair similarity of dizygotic twins. Thus, we had three objectives: First, we wanted to improve the quantification of EEG characteristics with respect to reproducibility and specificity by means of adaptive procedures and repeated measurements. Second, we wanted to compare the "typical" within-subject EEG similarity with the "typical" within-pair EEG similarity of monozygotic and dizygotic twins brought up together. Finally, we were interested in the degree to which environmental factors affect the characteristics of human brain-wave patterns. Our investigations were based on the empirical data derived from five different populations: (1) 81 healthy subjects, (2) 24 pairs of monozygotic twins brought up together, (3) 25 pairs of dizygotic twins brought up together, (4) 28 pairs of monozygotic twins reared apart, and (5) 21 pairs of dizygotic twins reared apart. Following our similarity conception, repeated measurements on the set of 81 individuals were used as design samples, and new registrations from the same individuals taken 14 days later were referred to as test samples in order to develop the appropriate method and to determine all required calibration parameters. This specific approach allowed us to construct EEG spectral patterns which, with a specificity and reproducibility of greater than 90% each, largely met the requirements of genetic EEG studies. Hence, we were able systematically to investigate the within-pair EEG similarity of our twin samples.(ABSTRACT TRUNCATED AT 400 WORDS)

Electroencephalography↗
PubMed2002

Adaptation to repeated cocaine administration in rats.

Quantitative electroencephalogram (EEG) studies in cocaine-dependent human patients show deficits in slow-wave brain activity, reflected in diminished EEG power in the delta and theta frequency bands. In the present study, electrophysiological measures were monitored in 10 nonanesthetized, adult male Sprague-Dawley rats via bipolar, epidural electrodes implanted over the somatosensory cortex. Control electrocorticograms (ECoG) were recorded twice within a two-week interval to establish a baseline. Rats were subsequently injected daily with cocaine HCl at 15 mg/kg, i.p., for two weeks. The ECoG was recorded during a 1-h session one day after the last injection. Total concentrations of dopamine (DA) and its metabolites were assayed in caudate nucleus (CN) and frontal cortex (FC) using HPLC/EC. Compared with controls, marked increases in DA concentrations were observed in both regions. The DA turnover decreased significantly. The power spectra, obtained by use of a fast Fourier transformation, revealed a significant decrease in slow-wave delta frequency bands following repeated exposure to cocaine. These data are consistent with reported findings in humans that repeated exposures to cocaine result in a decrease in slow-wave brain activity. Further studies are necessary to establish whether regional alterations in blood flow and metabolic activity may underlie such observations.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2003

Complementary therapy for addiction: "drumming out drugs".

OBJECTIVES: This article examines drumming activities as complementary addiction treatments and discusses their reported effects. METHODS: I observed drumming circles for substance abuse (as a participant), interviewed counselors and Internet mailing list participants, initiated a pilot program, and reviewed literature on the effects of drumming. RESULTS: Research reviews indicate that drumming enhances recovery through inducing relaxation and enhancing theta-wave production and brain-wave synchronization. Drumming produces pleasurable experiences, enhanced awareness of preconscious dynamics, release of emotional trauma, and reintegration of self. Drumming alleviates self-centeredness, isolation, and alienation, creating a sense of connectedness with self and others. Drumming provides a secular approach to accessing a higher power and applying spiritual perspectives. CONCLUSIONS: Drumming circles have applications as complementary addiction therapy, particularly for repeated relapse and when other counseling modalities have failed.

Acoustic Stimulation↗
PubMed1985

A comparison of physiological responses to percussive brain trauma in dogs and sheep.

Physiological variables were monitored in dogs and sheep after exposure of the brain to a pressure wave produced by a fluid-percussion device. Mean systemic arterial pressure (SAP), mean pulmonary arterial pressure (PAP), and pulmonary wedge pressure (PWP) were recorded prior to and following trauma. Lung lymph flows (QLYM) were measured prior to and for 2 hours after trauma. Plasma catecholamine levels were quantitated prior to and at 30 seconds following trauma. In 16 dogs, SAP increased from 123 +/- 14.6 to 254 +/- 60.8 mm Hg (p less than 0.0001), PAP increased from 17 +/- 4.4 to 27 +/- 10.8 mm Hg (p less than 0.05), and PWP increased from 4 +/- 2.4 to 15 +/- 8.8 mm Hg (p less than 0.0001), all at 30 seconds posttrauma. All pressures returned to near baseline values within 6 minutes. The QLYM from the right lymph duct in 12 dogs increased from 0.82 +/- 0.77 to 2.7 +/- 2.1 and 1.88 +/- 1.82 ml/30 min, respectively, at 30 and 120 minutes. In five dogs the plasma concentrations of dopamine, epinephrine, and norepinephrine increased from 234 +/- 98 to 1906 +/- 1384, 609 +/- 641 to 19,813 +/- 10,234, and 388 +/- 194 to 3223 +/- 992 pg/ml, respectively (all p less than 0.01). In sheep there were no changes in SAP, PAP, PWP, QLYM, or catecholamine levels in response to percussive wave trauma up to 10 atm. Ratios of lung tissue water to dry weight were not significantly different from control animals in either species. The authors conclude that in dogs there is a profound sympathetic discharge resulting in dramatic elevations in plasma catecholamines, systemic and pulmonary artery hypertension, and an increase in pulmonary lymph flow. Sheep fail to demonstrate changes in any of these variables after severe percussive wave brain trauma.

Animals↗
PubMed1987

How to use EEG/ERBP phenomena.

Hitherto the study of cerebral slow waves has been mainly empirical phenomenology, in spite of 50 years of effort to discover their origins and possible functions. Since 1970 the increasing use of both analog and digital filters, combined with more sensitive averaging techniques, has led to better understanding of some possible functional significance for the electroencephalogram (EEG) and the endogenous slow waves of event-related brain potentials (ERBP). The developing concepts and mathematics of non-linear dynamicsand coupled oscillators, when considered in the light of cerebral circuit geometry and topology, of local neuronal circuitry, and of both observed and experienced biological behavior, now offer hope for future, more complete, understanding of the development of 'conscious and goal-directed' activity from robotic and reflexive stimulus-response paradigms. Immediate practical results of a biophysical approach to brain waves should be: Models of vertebrate brains as distributed systems of non-linearly coupled oscillators; and revision of traditional methodologies for recording and interpreting EEG/ERBP data.

Afferent Pathways↗