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At least 19 recordsLinked to original sources
PubMed1998

Electrophysiological brain stem investigations in idiopathic narcolepsy.

Narcolepsy is associated with various rapid eye movement (REM) sleep abnormalities. Distinct brain stem areas seem to play a prominent role in REM sleep regulation. Recent magnetic resonance imaging (MRI) studies have led to conflicting findings concerning the presence of structural brain stem lesions in patients with idiopathic narcoleptic syndrome. However, multimodal electrophysiological brain stem investigations may reveal functional brain stem abnormalities even in the absence of MRI abnormality. Therefore we investigated brain stem function in 12 idiopathic narcoleptic patients by systematically studying tegmental brain stem pathways. All of the patients met the diagnostic criteria of the International Classification of Sleep Disorders, with typical changes in polysomnography and the multiple sleep latency test. Electrophysiological investigations comprised masseter reflex, blink reflex, masseter inhibitory reflex, early auditory evoked potentials and electrooculography with vestibular testing. In no patient were electrophysiological brain stem abnormalities observed. Our findings do not support the existence of a relevant brain stem lesion in narcoleptic patients with normal neurological status.

Adult↗
PubMed1992

Imaging of brain electrophysiologic activity: applications in psychiatry.

Recent advances in computer technology make it relatively easy to generate color images representing the electrophysiologic activity of the brain. Because of the visual appeal of the images, and their similarity to computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans, there has been wide interest in these methods. Thorough understanding of these techniques is necessary to appreciate their strengths and limitations, and their proper application. This article explains the types of studies that are usually done, compares these methods with other imaging techniques, outlines their limitations, summarizes the literature on their use in psychiatry, and describes clinical situations in which these tests may be useful. This information will help the reader interpret clinical reports and research studies that employ these methods, evaluate representations made by commercial vendors of imaging systems, and understand the role these tests can play in his or her daily clinical practice.

Brain↗
PubMed2004

Voltage-based versus factor score-based source localization analyses of electrophysiological brain activity: a comparison.

Though, traditionally, electrophysiological recordings have been limited to provide temporal information on neural activity, the development of mathematical algorithms capable of solving the inverse problem is facilitating, in recent years, the access to spatial information (i.e., on the origin of neural activation). This study explored a new strategy in order to increase the reliability of inverse problem solutions: applying these algorithms on factor scores (and not on voltages), a parameter that can be defined as "clean amplitude". Factor scores derive from Principal Component Analysis (PCA) applied to event-related potentials (ERPs). The main advantage of PCA is its capability to extract and quantify ERP components free of the influence of adjacent or subjacent components. The LORETA algorithm for source localization was applied on peak voltage, average voltage and factor scores for the motor potential recorded from 25 subjects, who had to repeatedly press a button with their right hand. The solutions given by LORETA in these three modalities were compared. The motor potential, a negative wave that begins just before any voluntary movement and is centrally distributed in the scalp, is particularly useful to the scope of this study, since its origin is known: contralateral motor cortex. Results show that the three modalities (peak voltage, mean voltage and factor scores) provided the same main focus (left motor cortex), though the "cleanest" solution (i.e., the main focus was more salient with respect to other secondary, noisy foci) was achieved by the factor score-based LORETA.

Adolescent↗
PubMed1998

A dual mechanism for sound pitch perception: new evidence from brain electrophysiology.

The N1 component of the auditory brain evoked potential was used as a direct electrophysiological index, to study how the perception of pitch for complex periodic tones can be influenced by the phase of the harmonics that make up a sound, according to their ranks. Results showed that in the low pitch and/or high spectra region, N1 latency was modified by phase, whereas it was not in the high pitch and low spectra region. These data help bring evidence towards a dual mechanism for pitch perception, and demonstrate that these processes take place within 110 ms following stimulus onset. Results are compatible with a model based on the resolvability of components and on the bandwidth of auditory filters.

Acoustic Stimulation↗
PubMed1996

Substance use disorder exacerbates brain electrophysiological abnormalities in a psychiatrically-ill population.

OBJECTIVE: To assess by brain electrical activity mapping whether cocaine and alcohol abuse and dependence would exacerbate electro-physiological abnormalities in a psychiatrically-ill population. DESIGN, SETTING, AND PARTICIPANTS: Utilizing a brain mapping system, we assessed EEG, Spectral Analysis (Quantitative EEG[QEEG]). Evoked Potentials (Auditory and Visual), and P300 (cognitive evoked potential), in a total of 111 probands divided into three groups: controls (N = 16), psychiatrically-ill without comorbid substance use disorder (N = 34), and psychiatrically-ill with comorbid substance use disorder (cocaine and alcohol abuse and dependence) (N = 61), at an outpatient neuropsychiatric clinic. With regard to demographic data, the group participating in this study did not differ significantly. A comparison was made among the groups to assist in differentiating the effects of substance use disorder compared to psychiatric disease on brain electrical activity. MAIN OUTCOME MEASURES: An assessment of electrophysiological abnormalities and their brain location in psychiatric and substance use disorder patients was done with a brain electrical activity mapping test. MAIN RESULTS: Among the non-substance use disorder, psychiatrically-ill (PI) and substance use disorder, psychiatrically-ill (PI/SD) groups, significantly different brain map abnormalities were observed relative to an assessed normal population MANOVA (P = .017). Moreover, with regard to Spectral Analysis, ANOVA was significant at a P = .038, and we found a weighted linear trend of increased abnormal total spectral analysis (P = .0113), whereby substance use was significantly worse than controls. Moreover among the PI and PI/SD groups, significantly greater total evoked potential (EP) brain trap abnormalities were observed when compared with a characterized normal population (P = .0023) with increasing abnormalities as a function of substance use disorder as measured by a weighted linear trend (P = .0022). In order to determine the site of the EPS abnormalities, we evaluated these abnormalities by location. In this regard, we found all temporal abnormalities (AVBITA, see Table 2) among the PI and PI/SD groups to be significantly greater relative to an assessed normal population (P = .0026). Furthermore, we observed a linear trend of increased temporal abnormalities with increasing substance use disorder (P < .0008). In terms of bitemporal abnormalities (AVBIT) among the PI and PI/SD groups, we also found significantly more bitemporal lobe abnormalities in the PI/SD group compared to our control population (P = .009). Additionally, a weighted linear trend of increased abnormal bitemporal lobe abnormalities was observed with increasing substance use disorder (P = .0022). In the frontal lobe similar findings were observed. With AVBIFA the ANOVA was P < .011, with a weighted linear trend of P < .005 and the PI/SD group were significantly more abnormal than PI or CS on a Duncan Range test. It is noteworthy that in a selected group of depressed (Major Depressive Disorder Recurrent, 296.3) patients, we found profound abnormalities in the various brain map parameters tested. MANOVA and Univariate ANOVA's revealed significantly greater abnormalities in the PI and PI/SD groups compared to assessed controls. A MANOVA for total brain abnormalities was significant at P = .043 and univariate ANOVA's for composite measurements of TSA (P = .017), EPS (P = .0002), AVBITA (P = .000015), and AVBIT (P < .00002) are also significant. With regard to EPS and AVBITA a weighted linear trend was observed where there were increasing abnormalities with increasing substance use disorder, P = .0001 and P = .000003, respectively. Most importantly we found that in addition to increased abnormalities with increasing substance use disorder the PI/SD group had significantly more abnormalities compared to the PI group with regard to both the TSA (P < .05) and AVBIT (P < .05) composite parameters as meas

Alcoholism↗
PubMed1988

V1-vasopressin receptors in the septum of the rat brain. Electrophysiological evidence.

In slices from the rat brain, extracellular recordings were obtained from single neurones located in the lateral septum, an area known to receive a vasopressinergic innervation. Approximately half of the neurones tested responded to vasopressin by a concentration-dependent increase in firing rate, the lowest effective concentration being in the order of 2 nM. The effect of vasopressin was blocked by a synthetic structural analogue possessing vasopressor and oxytocic antagonistic properties on peripheral vasopressin and oxytocin receptors. Oxytocin had a weak effect in firing septal neurones, whereas a selective oxytocic agonist was totally ineffective. The action of vasopressin on neuronal firing was mimicked by a vasopressor agonist (Phe2-Orn8-VT) but not by a selective antidiuretic agonist (dDAVP). These results indicate that the vasopressin receptors present in rat septum are V1 (vasopressor type) rather than V2 (antidiuretic type) receptors. In addition, we conclude that these receptors, when occupied, lead to increased firing of lateral septal neurones.

Action Potentials↗
PubMed1996

Electrophysiological brain activity and memory source monitoring.

To investigate brain mechanisms involved in identifying the origin of memories, event-related potentials (ERPs) were recorded as participants discriminated previously presented (old) from new items or identified their earlier source (picture, word, or new). Differences in ERPs between old-new recognition and source identification, were focused at frontal sites. For source identification, prominent negative deflections at occipital or frontal sites occurred depending on encoding task. These results support a model in which memory attributes are distributed neocortically and the frontal lobes are critical for source monitoring.

Adult↗
PubMed2006

Nanocomposite polymeric electrolytes to record electrophysiological brain signals in prolonged, unconventional or extreme conditions.

Chemically stable nanocomposite iono-conducting polymeric membranes (based on lithium salts and nanocrystalline oxide powders dispersed in a polymethyl methacrylate matrix) performed successfully in the recording of human brain responses to visual stimulation. Impedance was higher than that of conventional electrodes. However, the electrophysiological signals recorded by acid Al(2)O(3) and neutral Al(2)O(3) 5 wt.% and 10 wt.% nanocomposite gel electrolytes were comparable to those obtained with standard electrodes, even without preliminary skin cleaning and in the absence of gel electrolytes allowing better contact with and skin-electrode ionic conductance. The electrochemical and mechanical characteristics of these membranes make them fit for human and animal research, for clinical application (specifically in emergencies, prolonged electrophysiological recordings), or in unconventional or extreme conditions when fluid electrolytes are unsuitable (e.g., biomedical space research).

Animals↗
PubMedDate not supplied

Effects of uremia and dialysis on brain electrophysiology after recombinant erythropoietin treatment.

Quantitative electrophysiologic assessments are sensitive and useful indices of clinical state, and they are valuable in evaluating brain electrical activity before and after recombinant human erythropoietin (r-HuEPO) treatment. To study the hypothesis that, theoretically, anemia might be a cause of brain dysfunction in uremia, the authors assessed 18 patients (10 men and 8 women) on hemodialysis (RDT, age range, 35-58 years) before treatment (T1), and after 12 weeks (T2) and 24 weeks (T3) of r-HuEPO treatment, utilizing the following electrophysiologic tests: visual evoked potentials (VEP), brainstem auditory evoked responses (BAER), and somatosensory evoked potentials (SEP). The r-HuEPO was injected subcutaneously two times a week after RDT to produce hematocrit (Hct) levels of 30-35%. This drug induced a decrement of latency in P100 VEP (134.2 +/- 7.9 msec in T1 versus 116.5 +/- 6.9 msec in T2, p < 0.001, and versus 107.6 +/- 5.7 msec in T3, p < 0.005) and in the four main components of BAER. The most significant SEP changes were P27-N35 from peroneal nerve (p < 0.01), as an augmentation of SEP amplitude. Correction of anemia with r-HuEPO leads to a significant improvement in brain function in patients on RDT. The increased Hct level leads to enhanced brain oxygen delivery, directly improving brain metabolism. When the Hct rises, cerebral blood flow falls from high levels to normal, decreasing delivery of uremic "toxins" to the brain. The decrease in cerebral blood flow may decrease intracranial pressure and, in this way, may exert its beneficial effects by a rheologic pathway.

Adult↗
PubMed1984

Chronic lead exposure of the developing brain: electrophysiological abnormalities of cerebellar Purkinje neurons.

This manuscript reviews our recent research concerning electrophysiological effects of chronic low-level lead exposure on developing brain. We found that, although growth, survival and histological organization of in oculo cerebellar grafts appear normal after perinatal exposure to blood lead levels of 450 to 550 micrograms/liter, the physiological activity of Purkinje neurons in these lead-treated grafts is abnormally low after discontinuation of lead treatment. On the other hand, chronic low-level lead exposure postnatally via systemic injections or perinatally via the drinking water did not alter in situ cerebellar Purkinje cell activity. Moderate systemic doses (2 mg/kg) did cause a persistent slowing of Purkinje neuron firing rates; however, this effect was much smaller than in intraocular cerebellar grafts. The slowing may be mediated by lead actions on various transmitter systems. We have found that chronic lead induces catecholaminergic neurons to hyperinnervate target areas. Perhaps this hyperinnervation is initiated by the postsynaptic lead-induced blockade of the electrophysiological effects of norepinephrine which we have previously observed in the cerebellum in situ and in cerebellar grafts in oculo.

Action Potentials↗
PubMed2003

Deficient speech-sound processing, as shown by the electrophysiologic brain mismatch negativity response, and naming ability in prematurely born children.

Very low birth weight (VLBW, <1500 g) preterm birth has been associated with anatomic abnormalities in brain development and cognitive and language disorders. We examined object naming ability, and an electrophysiologic index of auditory sensory discrimination of speech sounds (the mismatch negativity, MMN) in 4-year-old VLBW prematurely born children. We found that half of the VLBW children were inferior to their controls in the object naming ability. Also the MMN amplitudes were smaller in the preterm group as compared with the controls. Further, the MMN amplitude varied as a function of children's performance on object naming, such that the weaker object-naming performance of the preterm group was paralleled by the diminished MMN amplitudes. Therefore, difficulties in auditory discrimination seem to be implicated in language difficulties encountered in VLBW prematurely born children.

Acoustic Stimulation↗
PubMed1990

Acute interactive pharmacologic effects of inhaled toluene and dichloromethane on rat brain electrophysiology.

Toluene (TOL) and dichloromethane (DCM) are widely used industrial solvents and are common components of solvent mixtures that are voluntarily inhaled to produce altered states of consciousness. In previous studies we characterized some of the acute electrophysiologic effects of these solvents. Opposite effects were noted for some measures, suggesting that they might be antagonistic when combined. In this study we examined the solvents again singly (10,700 and 16,000 ppm) and also in combination (16,000 ppm: 33/67 and 67/33% TOL/DCM ratios). The single gases caused effects similar to those observed previously. Combined effects varied, dependent upon the particular variable examined and the major gas in the mixture. In some respects the solvents were concordant, exerting similar effects on a variable, e.g., both solvents prolonged the latencies of components of the brainstem auditory-evoked response. In other respects they were discordant, e.g., whereas toluene caused mean EEG frequency to increase, dichloromethane had the opposite effect. Sometimes the solvents had similar effects alone, but acted independently in combination. Nonindependent interactions were also observed-both additive/subtractive or positively or negatively synergistic. The results further demonstrate and emphasize the unique patterns of acute central nervous system effects that can be effected by solvents that might have a common behavioral endpoint such as anesthesia, and the results characterize a variety of electrophysiologic interactions between these two solvents. Although there were several variables exhibiting synergistic relationships, independent or additive interactions were the most common.

Administration, Inhalation↗
PubMed1990

Effects of rare non-target stimuli on brain electrophysiological activity and performance.

In order to assess the effects of non-target stimuli on task performance and electrophysiological activity, 16 subjects performed reaction time (RT) experiments under 3 conditions. In all conditions, subjects had to press a button upon detection of rare (15%) target stimuli (1600 Hz) presented among frequent (85%) non-target stimuli. The 3 conditions differed based on their non-target stimuli. In one condition, the non-targets consisted of 'standard' stimuli (900 Hz). In the two other conditions, rare and deviant non-target stimuli were randomly added to the standard stimuli. These deviant non-target stimuli consisted of either constant (700-Hz tones) or novel (buzzes, filtered noises and other unusual sounds) stimuli. Both the rare target and non-target stimuli elicited P300, responses. Behavioral (RT) and electrophysiological (event-related potential) data showed that stimuli that followed standard stimuli were processed differently compared to stimuli that followed deviant non-target stimuli. In the conditions containing deviant non-target stimuli, the P3b to the target stimuli was smaller and later, and the mean RT longer than in the condition with no deviant stimuli. These behavioral and electrophysiological changes induced by the deviant non-target stimuli were discussed with reference to two factors, distraction and increased level of task difficulty. It was suggested that each of these factors were differentially sensitive to the novelty of the rare deviant stimuli.

Acoustic Stimulation↗