PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Brain waves”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed2000

Word deafness after resection of a pineal body tumor in the presence of normal wave latencies of the auditory brain stem response.

We studied the case of a 48-year-old woman who had resection of a pineal body tumor in terms of postoperative audiological function. Postoperative magnetic resonance imaging disclosed partial inferior colliculi destruction and medial geniculate body degeneration. A pure tone audiogram revealed only moderate sensorineural hearing loss, but her speech perception was totally impaired. The binaural sound localization function was also impaired. The auditory brain stem response (ABR) showed waves I, III, and V to have normal latencies. The amplitude of wave III was larger than that of wave V. These results support the view that the waves of the ABR are elicited from multiple sources in the auditory brain stem nuclei and tracts. This case suggests a substantial role for the inferior colliculus and medial geniculate body in the processing of speech perception and sound localization.

Astrocytoma↗
PubMedDate not supplied

Wave III of brain-stem auditory evoked potentials analysed both with 3-channel Lissajous' trajectory and dipole localization method.

Wave III of the BAEP was analysed both with 3-channel Lissajous' trajectory (3-CLT) and a dipole localization method. The experiments were performed on 5 normally hearing subjects. The dipole analysis used an iterative algorithm assuming a spherical head model and homogeneous media. 3-CLT planar analysis was performed with a laboratory system. The parameters of plane C (azimuth and elevation) corresponding to wave III and those of the equivalent dipole showed a similar orientation of the plane and the dipole. This result is in agreement with previous investigations and confirms the interest of 3-CLT in far-field analysis and, at the same time, validates the dipole localization model used in this study, at least for BAEP analysis.

Adult↗
PubMed2003

Optical analysis of depolarization waves in the embryonic brain: a dual network of gap junctions and chemical synapses.

Correlated neuronal activity plays a fundamental role in the development of the CNS. Using a multiple-site optical recording technique with a voltage-sensitive dye, we previously described a novel type of depolarization wave that was evoked by cranial or spinal nerve stimulation and spread widely over the whole brain region in the chick embryo. We have now investigated developmental expression and neuronal network mechanisms of this depolarization wave by applying direct stimulation to the brain stem or upper cervical cord of E5-E11 embryos, which elicited wave activity similar to that evoked by nerve stimulation. Spatial distribution patterns of the depolarization wave changed dynamically with development, and this change appeared to be related to the regional differences in neuronal differentiation. The depolarization wave was completely eliminated by application of either gap junction blockers or an N-methyl-D-aspartate (NMDA)-receptor antagonist, indicating that functions of both gap junctions and NMDA receptors are indispensable for wave propagation. A possible interpretation of the results is that dual networks of gap junctions and chemical synaptic coupling mediate large-scale depolarization waves in the developing chick CNS.

Animals↗
PubMed1983

Properties of the brain-stem response slow-wave component.

A slow-wave component of the brain-stem response recordable to signals at low sensation levels shows some promise for estimating hearing thresholds at low frequencies. This study describes several properties of this slow-wave response (SWR) in 30 normal hearing subjects and examines correlations with psychophysical thresholds. Acoustic signals were tone pips at 0.25, 0.5, 1, 2, and 4 kHz with 3-ms rise-fall times and no plateau. Repetition rate was 40/s. The EEG was filtered at 20 to 1,500 Hz before averaging. Results showed SWR thresholds were on the average about 15 dB higher than behavioral thresholds, however, the range was 0- to 35-dB sensation level. A large decrease in SWR amplitude and a 20-dB increase in threshold could occur in states of deep sleep. The SWR appears to be useful for estimating low-frequency thresholds, but the 35-dB threshold range in normal hearing subjects should be considered when interpreting some SWR results.

Acoustic Stimulation↗
PubMedDate not supplied

Neuroanatomic correlations with the late waves of the brain-stem auditory evoked potential.

The goal of this study was to investigate the neuroanatomic correlations of the late waves (VI-VIII) of the BAEP. Patients (N = 55) with clinical evidence of a CVA were compared to a normal control group (N = 85). Latencies of greater than 3 S.D. from the means of the normal group were considered abnormal. CT and MRI scans provided evidence of the lesions. For the 14 patients who had normal BAEPs, the sizes of lesions were significantly smaller than for those with abnormal tests. Evidence shows that an abnormal wave VI was related to an ipsilateral cortical lesion and an abnormal wave VIII was related to a lesion in the internal capsule-corpus striatum.

Adult↗
PubMed1999

Non-invasive optical monitoring of the newborn piglet brain using continuous-wave and frequency-domain spectroscopy.

We have used continuous-wave (CW) and frequency-domain spectroscopy to investigate the optical properties of the newborn piglet brain in vivo and non-invasively. Three anaesthetized, intubated, ventilated and instrumented newborn piglets were placed into a stereotaxic instrument for optimal experimental stability, reproducible probe-to-scalp optical contact and 3D adjustment of the optical probe. By measuring the absolute values of the brain absorption and reduced scattering coefficients at two wavelengths (758 and 830 nm), frequency-domain spectroscopy provided absolute readings (in contrast to the relative readings of CW spectroscopy) of cerebral haemoglobin concentration and saturation during experimentally induced perturbations in cerebral haemodynamics and oxygenation. Such perturbations included a modulation of the inspired oxygen concentration, transient brain asphyxia, carotid artery occlusion and terminal brain asphyxia. The baseline cerebral haemoglobin saturation and concentration, measured with frequency-domain spectroscopy, were about 60% and 42 microM respectively. The cerebral saturation values ranged from a minimum of 17% (during transient brain asphyxia) to a maximum of 80% (during recovery from transient brain asphyxia). To analyse the CW optical data, we have (a) derived a mathematical relationship between the cerebral optical properties and the differential pathlength factor and (b) introduced a method based on the spatial dependence of the detected intensity (dc slope method). The analysis of the cerebral optical signals associated with the arterial pulse and with respiration demonstrates that motion artefacts can significantly affect the intensity recorded from a single optode pair. Motion artefacts can be strongly reduced by combining data from multiple optodes to provide relative readings in the dc slope method. We also report significant biphasic changes (initial decrease and successive increase) in the reduced scattering coefficient measured in the brain after the piglet had been sacrificed.

Animals↗
PubMed2006

[Pathogenetic aspects of cochleovestibular disorders in shock-wave and mechanical impacts on brain structures].

The review concerns basic pathogenetic factors of shock-wave and mechanical effects on the structures of the brain (closed craniocerebral trauma, mine-explosion, baro-, acoustic trauma). When the brain and the labyrinth structures are exposed to traumatic mechanical or shock wave factors, the arising anatomic and functional defects damaging acoustic and vestibular analysers at different levels are similar. Concussion of the labyrinth provokes pathological alterations including circulatory disturbances, impaired production and composition of labyrinthine fluid and problems with its outflow leading finally to hydrops of the labyrinth.

Barotrauma↗
PubMed1980

Acute intracranial hypertension and auditory brain-stem responses. Part 3: The effects of posterior fossa mass lesions on brain-stem function.

The auditory brain-stem responses (BER's), infratentorial intracranial pressure (ICP), systemic blood pressure (BP), and heart rate were recorded before, during and after expansion of an infratentorial epidural mass in anesthetized cats. Two types of BER's to increasing posterior fossa pressure were noted. In Type 1, there was predominantly suppression of the electrical activity of the auditory nuclei of the upper brain stem (Waves V and IV) and upward transtentorial herniation of the midbrain. In Type 2, the neural activity of the lower brain-stem nuclei (Waves III and II) was affected as well as that of the upper brain stem. There was upward and foraminal impaction of the brain stem and cerebellum which was confirmed by the postmortem brain sections. The change in the amplitudes of BER Waves V and III proved useful in detecting upward transtentorial herniation of the midbrain and foraminal herniation of the cerebellum in acute expanding lesions of the posterior fossa. Medullary paralysis was also detected by observing Wave III.

Animals↗
PubMed1986

Changes of frequency spectrum of the CSF pulse wave caused by supratentorial epidural brain compression.

The frequency spectrum of the CSF pulse wave and amplitude transfer function from arterial to CSF pressure were estimated in the lateral ventricle and cisterna magna during the course of supratentorial epidural compression of brain in anaesthetised ventilated cats. Ventricular fluid pressure, the amplitude of spectral components of the CSF pulse and the amplitude of transfer function in the supratentorial compartment were increased in an exponential manner as epidural compression advanced. A transtentorial pressure gradient developed when epidural compression exceeded a critical level. Conduction of the CSF pulse through the tentorial hiatus decreased in an exponential manner when plotted against the transtentorial pressure gradient. Transtentorial conduction of the CSF pulse may serve as a sensitive indicator of the development of tentorial herniation.

Animals↗
PubMed1983

Properties of the brain-stem response slow-wave component. II. Frequency specificity.

Frequency specificity of a slow-wave response (SWR) of the brain-stem response (BSR) was measured with a simultaneous masking tuning-curve paradigm. The SWR tuning curves to 250-Hzz tone pips show greatest sensitivity to 350- to 400-Hz maskers. The SWR tuning curves to 500-Hz tone pips are most sensitive to 500- and 600-Hz maskers. Higher-frequency tuning curves show greatest sensitivity when masker frequency is equal to signal frequency. Frequency specificity is preserved to 80-dB sound-pressure level or 55- to 65-dB sensation level. Tone-pip frequencies of 0.5, 1.0, 2.0 and 4.0 kHz appear to be adequate stimuli for eliciting a frequency-specific SWR. The 250-Hzz tone pip does not elicit a frequency-specific SWR and is probably not a useful test frequency under the present recording conditions.

Acoustics↗
PubMed2001

Mapping adolescent brain change reveals dynamic wave of accelerated gray matter loss in very early-onset schizophrenia.

Neurodevelopmental models for the pathology of schizophrenia propose both polygenetic and environmental risks, as well as early (pre/perinatal) and late (usually adolescent) developmental brain abnormalities. With the use of brain mapping algorithms, we detected striking anatomical profiles of accelerated gray matter loss in very early-onset schizophrenia; surprisingly, deficits moved in a dynamic pattern, enveloping increasing amounts of cortex throughout adolescence. Early-onset patients were rescanned prospectively with MRI, at 2-year intervals at three time points, to uncover the dynamics and timing of disease progression during adolescence. The earliest deficits were found in parietal brain regions, supporting visuospatial and associative thinking, where adult deficits are known to be mediated by environmental (nongenetic) factors. Over 5 years, these deficits progressed anteriorly into temporal lobes, engulfing sensorimotor and dorsolateral prefrontal cortices, and frontal eye fields. These emerging patterns correlated with psychotic symptom severity and mirrored the neuromotor, auditory, visual search, and frontal executive impairments in the disease. In temporal regions, gray matter loss was completely absent early in the disease but became pervasive later. Only the latest changes included dorsolateral prefrontal cortex and superior temporal gyri, deficit regions found consistently in adult studies. These emerging dynamic patterns were (i) controlled for medication and IQ effects, (ii) replicated in independent groups of males and females, and (iii) charted in individuals and groups. The resulting mapping strategy reveals a shifting pattern of tissue loss in schizophrenia. Aspects of the anatomy and dynamics of disease are uncovered, in a changing profile that implicates genetic and nongenetic patterns of deficits.

Adolescent↗
PubMed2002

Acetazolamide therapy for symptomatic plateau waves in patients with brain tumors. Report of three cases.

In this report, the authors describe three patients with malignant gliomas who experienced paroxysmal neurological symptoms triggered by standing. The symptoms were attributed to acute elevations of intracranial pressure, an uncommon phenomenon called "plateau waves." In each instance, the attacks occurred despite the fact that the patient was receiving dexamethasone therapy and stopped promptly with the addition of acetazolamide. Acetazolamide, an orally administered carbonic anhydrase inhibitor, appears to be a specific and effective therapy for this uncommon neurological disorder.

Acetazolamide↗
PubMed2004

Initial attempts at directly detecting alpha wave activity in the brain using MRI.

The "direct detection" of neuronal activity by MRI could offer improved spatial and temporal resolution compared to the blood oxygenation level-dependent (BOLD) effect. Here we describe initial attempts to use MRI to detect directly the neuronal currents resulting from spontaneous alpha wave activity, which have previously been shown to generate the largest extracranial magnetic fields. Experiments were successfully carried out on four subjects at 3 T. A single slice was imaged at a rate of 25 images per second under two conditions. The first (in darkness with eyes-closed) was chosen to promote alpha wave activity, while the second (eyes-open viewing a visual stimulus) was chosen to suppress it. The fluctuations of the phase and magnitude of the resulting MR image data were frequency analysed, and tested for the signature of both alpha wave activity and neuronal activity evoked by the visual stimulus. Regions were found that consistently showed elevated power in fluctuations of the phase of the MR signal, in the frequency range of alpha waves, during the eyes-closed condition. It was conservatively assumed that if oscillations occurred at the same frequency in the magnitude signal from the same region or at the same frequency in the phase or magnitude signal from other regions overlying large vessels or cerebrospinal fluid (CSF), then the phase changes were not due to neuronal activity related to alpha waves. Using these criteria the data obtained were consistent with direct detection of alpha wave activity in three of the four volunteers. No significant MR signal fluctuations due to evoked activity were identified.

Adult↗
PubMedDate not supplied

[The persistent negative potential provoked in different structures of the rat brain by a single wave of spreading cortical depression].

The persistent negative potential (PNP) developed after a single wave of cortical spreading depression (SD) in the cortex, hippocampus, thalamus, and caudate nucleus. The PNP lasted for about 3-4 hours, its amplitude was 6-7 mV in the ipsilateral and 3-4 mV in the contralateral structures. After development of bilateral primary cortical SD waves the amplitudes of the respective PNP were summed up and reached 9-11 mV. However, after the repeated waves of cortical SD produced with 15-30-min intervals, the PNP level remained unchanged. We think that the PNP is an electrographic manifestation of the well known persistent vasoconstriction after a single wave of cortical SD. It seems to be related with reticular activation due to functional decortication.

Animals↗