[HARMONIC ANALYSIS OF CEREBRAL ELECTRIC WAVES].
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Automation↗
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Results for “Brain waves”
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EFFECT OF PERIPHERAL VESTIBULAR AFFERENT IMPULSES ON SYNCHRONIZATION OF SLOW CORTICAL WAVES.
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Brain↗
[Action of decimeter-range waves and of sinusoidal modulated currents on the nuclear DNA content of brain nerve cells (an experimental study)].
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Animals↗
Persistent vegetative state--clinical and electrophysiologic observations of 5 cases.
Five patients who met the criteria of the persistent vegetative state (PVS), were studied for ten years. Among them, two had fallen into a deep coma after cardiopulmonary resuscitation, and the other three cases were due to cerebrovascular disorders. Four patients died within 10 years. Clinically, all five cases showed characteristic features of wakefulness without cognitive function and movement of the extremities. The brain stem reflexes, such as light reflexes of the pupils and corneal reflexes, were present. The electroencephalograms showed ample low amplitude and nonspecific slow waves. None revealed an isoelectric pattern. Brain stem auditory evoked potential (BAEP) studies were normal or slightly abnormal. Median nerve somatosensory evoked potential (SSEP) studies showed absence of a cortical response. These features suggest that the damage in PVS patients is mainly located in the cerebral cortex. Although electrophysiologic examinations are useful diagnostic procedures for PVS, clinical observation remains the basis of the diagnosis.
Adult↗
Laryngeal mask airway for management of a difficult airway and extracorporeal shock wave lithotripsy.
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Child↗
Effects of rise time on simultaneously recorded auditory-evoked potentials from the early, middle and late ranges.
The view that the effects of stimulus rise time are qualitatively different for early brain stem components, middle latency components and late vertex components of the auditory-evoked responses was reexamined. The amplitudes and latencies of the brain stem response (Jewett's wave V), middle latency components Na and Pa, and vertex potentials P1, N1 and P2, evoked by tone burts of various rise times, were analyzed. Increases in rise time were associated with smaller peak amplitudes and longer peak latencies for all of the components measured. These effects were comparable in magnitude for all the components. The results are interpreted in terms of a delayed and less synchronized neural discharge from the cochlea as rise time is extended.
Adult↗
Effect of errors in baseline optical properties on accuracy of transabdominal near-infrared spectroscopy in fetal sheep brain during hypoxic stress.
A continuous-wave (cw) near-infrared spectroscopy (NIRS) instrument has been developed to noninvasively quantify fetal cerebral blood oxygen saturation (StO2). A linear Green's function formulism was used to analytically solve the photon diffusion equation and extract the time-varying fetal tissue oxy- and deoxy-hemoglobin concentrations from the NIR measurements. Here we explored the accuracy with which this instrument can be expected to perform over a range of fetal hypoxic states. We investigated the dependence of this accuracy on the accuracy of the reference optical properties chosen based on the literature. The fetal oxygenation of a pregnant ewe model was altered via maternal aortic occlusion. The NIR cw instrument was placed on the maternal abdomen directly above the fetal head, continuously acquiring diffuse optical measurements. Blood was sampled periodically from the fetus to obtain fetal arterial saturation (SaO2) measurements from blood gas analysis. The NIR StO2 values were compared with the fetal SaO2 measurements. Variations in the NIR results due to uncertainty in the reference optical properties were relatively small within the fetal SaO2 range of 30 to 80%. Under hypoxic conditions, however, the variability of the NIR StO2 calculations with changes in the assumed reference properties became more significant.
Abdomen↗
Lennox-Gastaut syndrome: potential mechanisms of cognitive regression.
Lennox-Gastaut (L-G) syndrome is an intractable generalized epilepsy of childhood onset, associated with spike waves at a slow rate and paroxysmal fast activity. These epileptiform discharge patterns are thought to reflect excessive neocortical excitability and arise from neuronal and synaptic features peculiar to the immature central nervous system. The epileptic processes associated with L-G syndrome may lead to enduring patterns of abnormal activity and connectivity. These abnormal patterns compete with normal developmental mechanisms and may result in subsequent impairment and/or regression of cognition. Recurring or prolonged seizures themselves may also damage the brain. We hypothesize that the presence of slow spike waves diverts the brain from normal developmental processes toward seizure-preventing mechanisms. Adding to this burden, antiepileptic medications, sleep disruption, and social isolation all retard cognitive development and the learning process at a crucial time of brain maturation.
Brain↗
Orthostatic mesodiencephalic dysfunction after decompressive craniectomy.
An extreme syndrome of the trephined after decompressive craniectomy is reported here. The most extensive clinical syndrome observed was established over 4 weeks and consisted of bradypsychia, dysartria, and limb rigidity with equine varus feet predominating on the right. The syndrome was aggravated when the patient was sitting with the sequential appearance over minutes of a typical parkinsonian levodopa-resistant tremor starting on the right side, extending to all four limbs, followed by diplopia resulting from a left abducens nerve palsy followed by a left-sided mydriasis. All signs recovered within 1-2 h after horizontalisation. It was correlated with an orthostatic progressive sinking of the skin flap, MRI and CT scan mesodiencephalic distortion without evidence of parenchymal lesion. Brain stem auditory evoked potential wave III latency increases were observed on the right side on verticalisation of the patient. EEG exploration excluded any epileptic activity. Symptoms were fully recovered within 2 days after cranioplasty was performed. The cranioplasty had to be removed twice due to infection. Bradypsychia, speech fluency, limb rigidity and tremor reappeared within a week after removal of the prosthesis. While waiting for sterilisation of the operative site, the symptoms were successfully prevented by a custom-made transparent suction-cup helmet before completion of cranioplasty.
Adult↗
The brain stem response SN10, its frequency selectivity, and its value in classifying neural hearing lesions.
The component P6 of the brain stem is only to be related to the hearing ability in the high tone range of greater than or equal to 2 kHZ, but it can be traced up to the hearing threshold. The cortex response N90, on the other hand, is frequency-specific, but it can hardly be recorded up to the subjective hearing threshold. The slow brain stem response SN10 (Davis and Hirsh 1979), unaffected by medicamented sleep, shall give information about hearing ability in the low and medium frequency range and may thus be an ideal complement to the fast response P6. In a number of normal hearing people and patients with sensorial hearing impairment of different frequency characteristics the brain stem responses P6 and SN10 were simultaneously recorded. As stimuli we used tone pips of a rise and fall time independent of frequency of about 2 ms and with a plateau of 2 ms as well. The mean threshold of the SN10 response is about 10 dB above the subjective hearing threshold. The constancy of the latencies corresponds to that of P6. The frequency selectivity of this relatively slow brain stem response is proved by comparing the P6 and SN10 responses with the course of the subjective hearing threshold. The topodiagnostic significance of the wave SN10 in connection with the brain stem response P6 and the cortical response N90 is shown in a case of neural hearing impairment.
Acoustic Stimulation↗
Loss of WAVE-1 causes sensorimotor retardation and reduced learning and memory in mice.
The Scar/WAVE family of scaffolding proteins organize molecular networks that relay signals from the GTPase Rac to the actin cytoskeleton. The WAVE-1 isoform is a brain-specific protein expressed in variety of areas including the regions of the hippocampus and the Purkinje cells of the cerebellum. Targeted disruption of the WAVE-1 gene generated mice with reduced anxiety, sensorimotor retardation, and deficits in hippocampal-dependent learning and memory. These sensorimotor and cognitive deficits are analogous to the symptoms of patients with 3p-syndrome mental retardation who are haploinsufficient for WRP/MEGAP, a component of the WAVE-1 signaling network. Thus WAVE-1 is required for normal neural functioning.
Animals↗
Muramyl peptide enhancement of slow-wave sleep.
Sleep-promoting Factor S, derived from brain or urine, has been characterized as a muramyl peptide. In rabbits, one pmol of Factor S induced excess slow-wave sleep (SWS) for several hours following cerebral intraventricular infusion. Factor S also induced increases in EEG slow-wave (1/2-4 Hz) amplitudes similar to those observed during the deep sleep that follows sleep deprivation. Sleep following Factor S treatment remained normal in that it was episodic and waking behaviours such as eating, drinking and grooming persisted. The structure of Factor S is similar to those of naturally occurring monomers of bacterial cell wall peptidoglycans. Other muramyl peptides such as muramyl dipeptide (MDP) were also found to be somnogenic. Structure-activity studies of various MDP derivatives indicated that somnogenic activity is dependent on precise structural requirements. Muramyl peptides also are immunomodulators and pyrogens. These activities could be separated from somnogenic activity by using various MDP derivatives or by pharmacologic intervention. Muramyl peptides may induce their somnogenic effects through the release of the cytokine interleukin-1; interleukin-1 also has the capacity to induce excess SWS. Although muramyl peptides have many biological activities in mammals, the role(s) they may play in mammalian physiology remains unknown. It is possible that mammalian tissue may store and/or modify muramyl peptides in conjunction with their use as modulators of sleep, temperature and immune responses.
Acetylmuramyl-Alanyl-Isoglutamine↗
[Correlation of the latency shift and brain stem potentials in basocochlear hearing loss and the time course of the click stimulus-induced evoked wave in the cochlea].
Frequency-specific information on high tone loss in the inner ear can, and if so only indirectly, be obtained from changes in latency of the click-evoked brain stem potential (ABR). The relationship between latency increases of the Jewett-wave-V in basocochlear hearing loss and the time course of the travelling wave on the basilar membrane will be presented. The latency increases of basocochlear hearing loss at 2 kHz, 1 kHz and 500 Hz correspond to both the computer-simulated time course of the travelling wave and to those of the derived responses. From a pathophysiological standpoint, receptor cells in basocochlear hearing loss are not functional, beginning at the oval window, so that, dependent on the degree of inactivity, a delay corresponding to that of the time course of the travelling wave passes until active hair cells are reached and action potentials released that produce, when summed up a potential of delayed latency.
Acoustic Stimulation↗
Magnetoencephalographic analysis of cortical oscillatory activity in patients with brain tumors: Synthetic aperture magnetometry (SAM) functional imaging of delta band activity.
Abnormal focal slow wave activity on electroencephalography and magnetoencephalography (MEG) is often seen in patients with various brain pathologies and MEG is capable of localizing cortical oscillatory activity with enhanced accuracy. In addition, MEG with synthetic aperture magnetometry (SAM) can depict changes in cortical oscillatory activity tomographically. Using SAM, we recorded cortical rhythms in patients with a brain tumor and evaluated the tomographic appearance of focal slow wave activity in relation to clinical signs and symptoms. Spontaneous MEG recordings were obtained in 15 patients with brain tumors. Statistically-determined power distributions in the delta-, theta-, and alpha-frequency bands were displayed tomographically and overlaid on individual magnetic resonance images. The location, strength and volume of enhanced activity were analyzed. Delta and theta band activities were significantly more intense in the cortex adjacent to tumors and in the surrounding edematous cortical areas than in other portions of the cortex. In 13 of the 15 patients, spatial distribution of enhanced focal delta activity coincided with the area responsible for the presenting signs and symptoms. Volumetric analysis revealed that emergence of tumor-related focal delta band activity in the cortex adjacent to a tumor, or with peritumoral edema, was greater for intra-axial tumors involving subcortical fibers than for extra-axial tumors. Patients with an increased volume of enhanced delta activity exhibited poor recovery of function in the early postoperative period. It is concluded that SAM imaging of focal delta activity can reveal functional alterations in cortical activity in patients with brain tumors and is useful for assessing cortical states associated with the existing pathology.
Adult↗
Polarization of the RF field in a human head at high field: a study with a quadrature surface coil at 7.0 T.
The RF field intensity distribution in the human brain becomes inhomogeneous due to wave behavior at high field. This is further complicated by the spatial distribution of RF field polarization that must be considered to predict image intensity distribution. An additional layer of complexity is involved when a quadrature coil is used for transmission and reception. To study such complicated RF field behavior, a computer modeling method was employed to investigate the RF field of a quadrature surface coil at 300 MHz. Theoretical and experimental results for a phantom and the human head at 7.0 T are presented. The results are theoretically important and practically useful for high-field quadrature coil design and application.
Brain↗
[Magnetic resonance of magnetically ordered nanoscale particles in brain tissue].
Nature of unusual resonance signals, which can be registered by spectrometers of electron paramagnetic resonance, are studied in different weakly mineralized biological tissues. The experiments are carried out in a three-centimeter range of waves on human and animal (rats) brain tissues and on the organic component of mollusk shells. In these materials the unusual resonance signals, which have unique dynamic characteristics, are registered. Analysis of the characteristics of the anomalous signals shows that the signals are produced by magnetically ordered particles, which have dimensions in nanoscale range. On the basis of experimental data the conclusions are made, that as a result of biomineralization processes in brain tissues both physiological and pathological mineral particles are formed. The supposition is made, that physiological particles play the important role in operation of a brain, and pathological can be a causes of brain diseases.
Animals↗
Electrical stimulation of the auditory nerve via cochlear implants in patients with auditory neuropathy.
Auditory neuropathy (AN) is a term used to describe an auditory disorder in which there is evidence of normal outer hair cell function (otoacoustic emissions and/or cochlear microphonics) and poor function of the auditory nerve (absent or highly distorted auditory brain stem response starting with wave I). Many of these patients have evidence of generalized peripheral nerve disease, leading to an assumption that the peripheral portion of the auditory nerve is the most likely site of lesion. A small group of these patients has received cochlear implants, and the majority of them achieve average to above-average performance. Although this outcome may seem incongruous with neural disease, average performance by patients with AN may be a result of the reintroduction of neural synchrony by electrical stimulation and/or the fact that most deaf patients have poor nerve survival. Although cochlear implants are promising for deaf patients with AN, more study of the disorder is needed.
Adult↗
[A case of cortical deafness with bilateral putaminal hemorrhage].
A 56 years old right-handed female, a housewife, had suffered from right putaminal hemorrhage which had been treated surgically in July, 1985. Since it was difficult to approach the trans-sylvian fissure, evacuation of the hematoma was performed transcortically through the superior temporal gyrus. She was neurologically free and lived normally until she suddenly became completely deaf in April, 1991. On admission, she was alert, well oriented and spontaneously stated that she was deaf. She showed no response to verbal commands or loud noises but followed complex written commands. No other neurological deficit was observed. In addition to an irregular low-density area in the right temporal lobe, CT scan revealed a left putaminal hemorrhage. Audiological testing disclosed pure tone thresholds to be below 90db on both sides. Auditory brain stem response (ABR) showed waves I to VI in normal latency ranges, but wave VII was not observed. She was treated conservatively. Although her hearing loss had been gradually improving for 1 month, she suffered from word deafness, an inability to comprehend speech, for the following 2 months. Clinical features, CT findings as well as results of ABR suggest that hearing loss observed in this case, cortical deafness, was presumably due to bilateral damage of acoustic radiation of the temporal lobe. It was also suggested that, although she was asymptomatic, cortical and subcortical damage to the right temporal lobe following evacuation of the putaminal hematoma may have been extensive. During surgical procedures for evacuation of the putaminal hematoma, it has to be always kept in mind not to damage the auditory cortex and its radiations.
Cerebral Hemorrhage↗