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At least 325 records · Page 18Linked to original sources

PubMed2003

[Convulsive syncope: characteristics and reproducibility using the tilt test].

OBJECTIVES: To establish the main clinical characteristics of convulsive syncope and the usefulness of the tilt test in its diagnosis. METHODS: A total of 317 patients (aged 5-18 years old) under clinical suspicion of neurocardiogenic syncope underwent a multiparametric tilt test. Our tilt test protocol includes continuous noninvasive measurement of heart rate, blood pressure, and arterial oxygen saturation, as well as continuous noninvasive measurement of cerebral oxygen saturation by near-infrared spectrophotometry. In selected patients, simultaneous electroencephalogram (EEG) was performed. RESULTS: The tilt test was positive in 216 patients (68.1 %). Of these, 25 (11.6 %) showed seizures during the test (convulsive syncope). Convulsions were asymmetric-tonic in 15 patients (60 %), generalized tonic in 5 (20 %), and tonic-clonic in 5 (20 %). In all patients, convulsive episodes lasted less than 30 seconds and spontaneously ceased upon placing the patient in a horizontal or Trendelenburg position. When simultaneous EEG was performed, diffuse brain wave slowing was observed, without paroxysmal activity. CONCLUSIONS: Convulsive syncope is not an uncommon event in children and is easily elicited by means of the tilt test. Pediatricians should be aware of this finding in order to avoid the frequently established unidirectional association between seizures and epileptic disorders. Consequently, the tilt test should be considered an essential tool in the differential diagnosis between convulsive syncope and epilepsy.

Adolescent↗

PubMed1994

Relationship of electroencephalographic and cardiovascular changes to plasma nicotine levels in tobacco smokers.

OBJECTIVE: The effects of smoking one tobacco or placebo cigarette on the mean change in voltage of the electroencephalogram (EEG), arterial blood pressure, heart, and eye blink rates were correlated with the increase in plasma nicotine, exhaled carbon monoxide, and carboxyhemoglobin levels. METHODS: Twenty nonsmokers (age range, 19 to 42 years; mean age +/- SE, 27.0 +/- 1.9 years) and 65 regular tobacco smokers (age range, 20 to 48 years; mean age +/- SE, 27.7 +/- 0.8 years) were studied about 10 to 12 hours after overnight tobacco deprivation and immediately after inhaling air through a straw or after smoking one of their own brands of cigarettes, respectively. RESULTS: An increase of at least 10 ng/ml plasma nicotine was needed to obtain a statistically significant decrease in alpha 1 and an increase in beta EEG activity. An increase of at least 15 ng/ml plasma nicotine was needed to obtain a statistically significant decrease in delta EEG activity. The mean dominant alpha frequency, heart rate, systolic and diastolic blood pressure, exhaled carbon monoxide, and carboxyhemoglobin levels increased significantly with increasing plasma nicotine concentrations. CONCLUSIONS: Measurement of plasma nicotine levels is especially important to quantify the relationship between tobacco smoking, mean EEG activity, and cardiovascular changes. Nicotine plasma concentrations greater than 10 micrograms/ml produce consistent and statistically significant changes in brain wave activity. Smaller increments in plasma nicotine produce less consistent EEG changes.

Adult↗

PubMed2002

The effectiveness of a hands-free environmental control system for the profoundly disabled.

OBJECTIVE: To investigate the effectiveness of a hands-free environmental control system (ECS) that allows profoundly disabled persons to activate and control electric devices in their home by using consciously controlled changes in their brain signals. DESIGN: A cohort study with a field trial testing of the ECS on 3 occasions. SETTING: Participants' homes. PARTICIPANTS: Ten profoundly disabled persons (mean age, 42.9 y), all of whom had very limited movement from the neck downward. Six had spinal cord injury with lesions ranging from C2 to C5-6. The other 4 had profound disability (1 each from polio, spinal muscular atrophy, multiple sclerosis, cerebral palsy). INTERVENTIONS: Participants performed tasks on each of 3 test occasions. The tasks consisted of turning a television on at the beginning of the trial, changing channels (up, down), changing volume, and turning it off at the conclusion of each trial. MAIN OUTCOME MEASURES: Time participants took to select the correct option and number of errors made in selecting the correct option. Measures were taken for each trial, so that any improvement in switching could be detected. RESULTS: All participants effectively used the ECS to operate their television sets. Selecting a correct option took about 30 seconds (with the majority of this time attributed to machine cycling time), with an error rate of 1.8 per 5 options selected. The time taken to operate the ECS reduced slightly over the 3 trials and selection errors reduced by around 50% (to less than 1 error per 5 options). CONCLUSIONS: With minimal training, profoundly disabled persons were able to use an ECS that uses changes in brain wave signals. This result demonstrates the efficacy of an additional and novel ECS in an area in which few switches are available.

Adult↗

PubMed1989

Intermittent chaos, self-organization, and learning from synchronous synaptic activity in model neuron networks.

Self-organization of frequencies is studied by using model neurons called VCONs (voltage-controlled oscillator neuron models). These models give direct access to frequency information, in contrast to all-or-none neuron models, and they generate voltage spikes that phase-lock to oscillatory stimulation, similar to phase-locking of action potentials to oscillatory voltage stimulation observed in Hodgkin-Huxley preparations of squid axons. The rotation vector method is described and used to study how networks synchronize, even in the presence of noise or when damaged; the entropy of ratios of phases is used to construct an energy function that characterizes organized behavior. Computer simulations show that rotation numbers (output frequency/input frequency) describe both chaotic and nonchaotic behavior. Learning occurs when synaptic connections strengthen in response to stimulation that is synchronous with cell activity. It is shown that intermittent chaotic firing is suppressed and simple stable responses are enhanced by such learning in VCON networks. This analysis provides a rigorous basis for further investigation of the ideas of Wiener [Wiener, N. (1961) Cybernetics (MIT Press, Cambridge, MA), p. 191] on the origin of slow brain waves due to "the pulling together of frequencies."

Action Potentials↗

PubMed1994

Natural sleep modifies the rat electroretinogram.

We show here electroretinograms (ERGs) recorded from freely moving rats during sleep and wakefulness. Bilateral ERGs were evoked by flashes delivered through a light-emitting diode implanted under the skin above one eye and recorded through electrodes inside each orbit near the optic nerve. Additional electrodes over each visual cortex monitored the brain waves and collected flash-evoked cortical potentials to compare with the ERGs. Connections to the stimulating and recording instruments through a plug on the head made data collection possible at any time without physically disturbing the animal. The three major findings are (i) the ERG amplitude during slow-wave sleep can be 2 or more times that of the waking response; (ii) the ERG patterns in slow-wave and REM sleep are different; and (iii) the sleep-related ERG changes closely mimic those taking place at the same time in the responses evoked from the visual cortex. We conclude that the mechanisms that alter the visual cortical-evoked responses during sleep operate also and similarly at the retinal level.

Animals↗

PubMed1992

Functional 3D localization of cerebrovascular accidents by magnetoencephalography (MEG).

Spontaneous magnetic slow wave brain activity can be used to locate the underlying sources with sufficient accuracy by using the single current dipole model. To locate focal sources from spontaneous activity a tool had to be developed to extract focal densities of dipoles across time-the dipole density plot. The first version works on discrete volume units and is used for screening. The second version avoids a possible localization error and works continuously and this even is done on individual slices. The DDP seems to be a valuable tool for extracting and separating different focal sources from the background activity. Not only brain infarctions and haemorrhages (and cysts and angiomas) could be located, but also functional sources associated with TIAs even one week after the symptoms. First results let us assume that clinically silent TIAs also (in analogy to clinically silent brain infarctions) could be detected and located.

Brain↗

PubMed2002

The auditory steady-state response is not a suitable monitor of anesthesia.

UNLABELLED: Previous studies show that the human 40-Hz auditory steady-state response (ASSR) disappears on induction of general anesthesia, suggesting that it may be a good candidate for a monitor of anesthesia. In this study, we aimed to learn whether all normal alert adults display ASSRs with adequate signal-to-noise ratio. Clicks were presented at a series of frequencies between 35 and 70 Hz and electroencephalographic records taken at the vertex were Fourier transformed. ASSRs were observable as sharp peaks in the electroencephalograph spectrum at the frequency of the clicks. Initial results showed that a discernible ASSR could not be obtained from about half the subjects studied at any click frequency used. Further investigation revealed that in subjects whose ASSR was undetectable in the alert state, induction of a drowsy mental state resulted in appearance of an observable ASSR. This was attributable to an increase in signal in the drowsy state, not to a decrease in noise. We conclude that, because a significant proportion of subjects do not display easily recordable ASSRs when alert, it is not practical to use disappearance of the ASSR as a routine test for adequacy of anesthesia. IMPLICATIONS: Auditory steady-state responses (ASSRs) are brain waves evoked by auditory stimuli. Because they reportedly disappear under general anesthesia, they have been suggested as potential indicators of anesthetic depth. However, in this study, we show that about half our normal adult subjects did not produce measurable ASSRs when awake. This suggests that ASSRs are not good candidates for use in monitoring anesthetic depth during surgery.

Acoustic Stimulation↗

PubMed2004

Detecting dynamical changes in time series using the permutation entropy.

Timely detection of unusual and/or unexpected events in natural and man-made systems has deep scientific and practical relevance. We show that the recently proposed conceptually simple and easily calculated measure of permutation entropy can be effectively used to detect qualitative and quantitative dynamical changes. We illustrate our results on two model systems as well as on clinically characterized brain wave data from epileptic patients.

Journal Article↗

PubMed1990

A new mode of communication between man and his surroundings.

The material presented in this paper is the result of a research project that was designed to study the feasibility of establishing an alternative mode of communication between man and his surroundings. The new form of communication proposed uses only the subject's brain waves with no overt physical action required. Subjects' electroencephalograms (EEG) were recorded while they performed various mental tasks designed to elicit hemispheric responses. Features formed from the EEG recording were then used as inputs into a Bayes quadratic classifier to test classification accuracy between the various tasks. The results obtained indicate that it is possible to accurately distinguish between any pair of the five tasks investigated. A comparison between three different methods for creating the feature sets is also presented.

Adult↗

PubMed2004

Electrogastrographic biofeedback: a technique for enhancing normal gastric activity.

Biofeedback has been used effectively for approximately 40 years as a technique to help individuals learn to control muscle activity, brain waves, certain autonomic nervous system responses such as heart rate and blood pressure, and, more recently, constipation and fecal and urinary incontinence. In the present study, biofeedback of electrogastrographic (EGG) activity was used to determine the extent to which healthy subjects could increase normal 3 cpm gastric myoelectric activity. Thirteen experimental participants were provided with biofeedback of their EGG activity on a computer screen, and instructed to try to make their own EGG signal match a simulated 3 cpm signal that was also present on the screen. Subjects were told to relax using various forms of imagery, and to heighten their awareness of their stomach activity. Thirteen control participants did not receive any biofeedback but were otherwise given the same instructions. Both groups showed an increase in 3 cpm activity while relaxing. However, over four trials separated by 2-7 days, experimental participants showed an increased percentage of 3 cpm activity during biofeedback sessions, while control participants showed a decrease in 3 cpm activity during the corresponding sessions. In conclusion, we have demonstrated that healthy subjects can increase their normal gastric 3 cpm activity with the use of EGG biofeedback.

Adolescent↗

PubMed1996

The clinical features of Tourette's disorder with obsessive-compulsive symptoms.

Twenty-three patients with Tourette's disorder (13 with obsessive-compulsive symptoms [OCS] and 10 without) were comparatively investigated. In contrast to OCS-free Tourette's disorder patients, those with OCS were found to be characterized by (i) a higher incidence of volatile temper, (ii) a higher incidence of compulsive tics, (iii) a higher incidence of perinatal disorders and brain wave abnormalities, (iv) a higher severity as rated using the Severity Scale, and (v) a higher prevalence of complications, especially of developmental disorders. Of the subjects with OCS-accompanied Tourette's disorder, approximately half had developed OCS by the onset of tics. These findings suggest the likelihood that OCS-accompanied Tourette's disorder is more strongly associated with organic cerebral disorders, independently of sites of tic disorders, than is OCS-free Tourette's disorder.

Adolescent↗

PubMed2005

Changes in electroencephalographic activities following pressure stimulation in humans.

We investigated brain activity in response to orofacial pain in 20 healthy subjects in order to characterize the relationship between pain and changes in brain function. First, the pressure pain threshold (PPT) at the styloid process of the temporal bone (Libman's point) of 20 subjects was measured by a pressure algometer. Second, electroencephalographic (EEG) changes of 20 subjects before and after 10 s of constant pressure stimulation at Libman's point were measured. These 20 subjects were divided into two groups: 10 subjects with higher PPT (high group) and 10 subjects with lower PPT (low group). EEG change in beta activity after stimulation was greater in the low group than the high group, and there was a significant negative correlation between this change and PPT, with even minor constant stimulation inducing larger EEG change in individuals highly receptive to pain. The present study demonstrated that a relative reduction in beta activity after pain stimulation was more remarkable in subjects with lower PPT than in subjects with higher PPT, and that this change was closely related to a hemispheric balance, with even minor constant stimulation inducing changes in brain waves in individuals highly sensitive to pain.

Adult↗

PubMed1985

Genetics of alcoholism.

Great progress has been made by research on the contribution genetic factors make to a vulnerability toward alcoholism. Animal studies have demonstrated the importance of genetics in ethanol preference and levels of consumption, and human family, twin, and adoption research have revealed a 4-fold higher risk for offspring of alcoholics, even if they were adopted out at birth. The work presented in this symposium reviews the ongoing search for genetic trait markers of a vulnerability toward alcoholism. Dr. Li has used both animal and human research to demonstrate the possible importance of the genetic control of enzymes involved in ethanol metabolism and has worked to help develop an animal model of alcoholism. The possible importance of subgroups with different levels of predisposition toward alcoholism is emphasized by Dr. Cloninger. An overview of the studies of sons of alcoholics, given by Dr. Schuckit, reveals the potential importance of a decreased intensity of reaction to ethanol as part of a predisposition toward alcoholism and discusses the possible impact of some brain waves and ethanol metabolites to an alcoholism vulnerability. Dr. Deitrich reviews interrelationships between studies of animals and humans in the search for factors involved in a genetic vulnerability toward alcoholism. Taken together, these presentations underscore the importance of genetic factors in alcoholism, review animal and human research attempting to identify markers of a vulnerability, and reveal the high level of interaction between human and animal research.

Adoption↗

PubMed1971

Anemia in sleep-deprived rats receiving anticoagulants.

Independent groups of rats were deprived of sleep and treated with the anticoagulant drugs phenylindanedione or dicoumarol for 1 to 8 days. These animals developed an extremely severe anemia which was accelerated by p-chlorophenylalanine. The red cell count and amount of hemoglobin decreased to half of normal values. No decrease occurred in animals subjected to any one single treatment. Histological examination indicated hemolysis, hypoplasia of hemopoietic organs, slight hemorrhage, but no evidence of stress. The severity of the anemia was inversely related to the amount of sleep permitted during sleep deprivation. This new syndrome demonstrates marked effects of sleep deprivation on both maturation and destruction of red blood cells. Depletion of serotonin by injection of parachlorophenylalanine blocked the increase in amount of brain waves of the type commonly seen in slow wave sleep but did not eliminate the production of these waves. This result is at variance with the theory that serotonin is the neurochemical responsible for the "priming" of slow wave sleep.

Anemia↗

PubMed1984

Genetic factors in depression and suicide.

There is a large body of evidence implicating a genetic factor in major affective disorder, particularly bipolar type. Studies of family risk, of twin concordance, and of adoptees and their families have contributed to this consensus. In the case of suicide, completed or attempted, the evidence is less clear. Twin studies have been based on a small number of pairs and have been inconclusive, and family and adoption studies have not yet satisfactorily separated suicide risk from risk for depression. Biological studies involving neurotransmitter levels suggest that suicide even without depression may be uniquely characterized, and there have been reports of associated brain-wave dysfunction. The interacting role of psychological or biological precipitating factors with the genetic component of psychosis or personality disorder still needs further clarification.

Adoption↗

PubMed1990

Fetal drug exposure and its possible implications for learning in the preschool and school-age population.

For the past 5 years there has been an exponential increase in the use of cocaine, phenylcyclidine hydrochloride (PCP), and other central nervous system (CNS) active drugs. A significant amount of this accelerated usage is in sexually active females, resulting in some urban hospitals reporting positive drug screens in over 16% of the infants born on their busy obstetrical service. There is a growing body of data showing that fetal exposure to cocaine, phenylcyclidine hydrochloride (PCP), and other CNS-active drugs results in infants and children with abnormal brain wave patterns, short-term neurologic signs, depression of interactive behavior, and poor organizational responses to environmental stimuli. Whether such neurologic findings will translate into a significant number of children with learning and behavioral problems needs to be the focus of long-term longitudinal studies of children with fetal drug exposure to cocaine, PCP, and other CNS-active drugs.

Child↗

PubMed1962

Electroencephalographic correlates of temporally spaced responding and avoidance behavior.

This study was undertaken to determine whether any EEG changes occurred during a multiple schedule of reinforcement consisting of repeated periods of avoidance behavior, a time-out (TO) period, and a period of differential reinforcement of low rates (DRL). The two monkeys were permanently implanted with bipolar electrodes in various subcortical areas. The EEG was recorded from these electrodes for several weeks before any behavioral training was undertaken. Training was then begun in the multiple schedule, and EEG recordings were taken frequently throughout the training period. When a stable performance level was achieved, drugs (dl-amphetamine and sodium pentobarbital) were introduced which disrupted the DRL performance but had little or no effect on avoidance behavior. The EEG recordings continued throughout these drug studies. The data indicate that the marked behavioral differences noted in each component of the schedule were not reflected in the EEG. However, the EEG did correlate with the general level of alertness of the animals during the various components. The drugs which differentially affected the behavior in the components of the schedule did not differentially affect the EEG, but they did change the brain-wave activity equally in all components. Finally, EEG changes correlated with the complex motor response of lever pressing were not observed.

Animals↗

PubMed1995

Cortical auditory disorder caused by bilateral temporal infarctions.

We present a 55-year-old man who suddenly became afflicted with a bilateral auditory disturbance. Auditory acuity was preserved relatively well. Brainstem auditory evoked potentials (BAEPs) were normal. Middle latency auditory evoked potentials (MLAEPs) revealed the total absence of all waves. Brain computed tomography (CT) showed infarctions of the temporal lobes bilaterally, involving the superior temporal and transverse temporal gyri. The recognition of verbal and nonverbal sounds was also impaired. Brain CT, MLAEPs and auditory recognition tests were useful in diagnosing the cortical auditory disorder.

Auditory Diseases, Central↗