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At least 685 records · Page 38Linked to original sources

PubMed1990

Autoregression models of EEG. Results compared with expectations for a multilinear near-equilibrium biophysical process.

This paper considers the properties of parameters (natural frequencies and damping coefficients) obtained from segment-by-segment autoregression analysis of ECoG of rat. The use of a reference signal as control for parameter estimate errors, and multiple regression analyses indicate that the dependencies among parameters calculated from ECoG in the alert (desynchronised) state are of a form consistent with imposition of time-invariance assumptions (implicit in autoregression) on an inherently non-stationary, multimodal, linear and near-equilibrium "thermal" process.

Animals↗

PubMed1981

Effects of changes in cortical arousal and of auditory cortex cooling on neuronal activity in the medial geniculate body.

The activity of cells in the medial geniculate body (MGB) of adult cats was recorded during different states of cortical arousal with and without cooling of the auditory cortex. In the absence of auditory cortex cooling, the overall mean unit spontaneous discharge rate was 49% higher during desynchroized Electrocorticogram (ECoG) periods (high cortical arousal). Responses to sound were somewhat more prominent vis-à-vis the spontaneous activity during periods of high arousal. Changes in spontaneous discharge rate associated with arousal shifts were significantly reduced during auditory cortex cooling. When the ECoG changed from desynchronized to synchronized activity, MGB cells showed a change in discharge pattern, typically characterized by an increase in both high-rate bursts and long-interval pauses. These changes were duplicated for most cells by cooling of the auditory cortex. Corticofugal fiber discharge thus has an effect on MGB neuronal activity which is dependent on the level of cortical arousal. This effect is most likely a result of direct corticogeniculate activity, though indirect auditory cortex - brainstem - MGB routes may also be involved.

Animals↗

PubMed1975

Non-surgical recording of auditory pathway function in cats.

The techniques are described for serial, non-surgical recording of the cochlear microphonic (CM), the electrocochleogram (ECoG) and the averaged electroencephalic response (AER) in cats. The early post-natal period has been systematically studied in a breeding strain of hereditarily deaf white cats, and illustrative examples are presented from animals with histologically normal chochleae, and also from ears with confirmed chochleosaccular degeneration. Transitory potentials have been recorded with the CM and ECoG procedures from some of the latter.

Age Factors↗

PubMed1981

The release of endogenous GABA and glutamate from the cerebral cortex in the rat.

1. The release of endogenous GABA and glutamate from the cerebral cortex was measured using a cortical cup technique in unanaesthetized freely moving rats and anaesthetized rats by means of a sensitive and specific mass-spectrometric procedure. 2. GABA release was not affected by the presence of the dura mater or by anaesthesia. Glutamate output was reduced by urethane but not by pentobarbital anaesthesia and by the presence of the dura. 3. An isotonic solution containing 50 mM KCl placed epidurally within the cup elicited a significant short-lasting increase in glutamate output, a decrease in GABA output and a short-lasting electrocorticogram (ECoG) activation. 4. When the dura was removed, a high K+ solution placed on the exposed cerebral cortex elicited a 7--8 fold increase in GABA output accompanied by a marked decrease in glutamate output and by ECoG synchronization. The changes in GABA and glutamate output had parallel time-course and were prevented by the application within the cup of tetrodotoxin (3 X 10(-5) M). 5. Amphetamine at the doses of 3.7 and 7.4 mumol . kg-1 i.v. increased glutamate output and at the dose of 37 mumol . kg-1 i.v. increased GABA output. Both effects were prevented or reduced by haloperidol pretreatment (0.65 mumol . kg-1 i.v.). 6. It is concluded that GABA and glutamate released from the cerebral cortex and diffused into an epidural or cortical cup originate at least in part from the brain. The rate of their release is influenced by changes in neuronal activity. The measurement of their rate of release offers a useful tool for the study of the functional role of cortical GABA and glutamate-releasing neurons.

Amino Acids↗

PubMed1975

Ventral midbrain stimulation, blood pressure responses and their relation to the dopaminergic nigro-striatal pathways.

In 40 cats systematic, electrical stimulation of ventral midbrain structures was performed. In the lightly anaesthetised animals, fixed in a stereotaxic frame, ECoG and arterial blood pressure were registrated. As a result stimulation-induced phasic blood pressure increases have been found within a distinct area including substantia nigra and ventral tegmentum. From the same region nonspecific responses in the ECoG (spindling, recruiting and desynchronisation by low and middle frequent stimulation) could be obtained. The blood pressure responses were enhanced after hemisection at the level of the posterior hypothalamus ipsilateral to the stimulation side. Drugs (Haloperidol, alpha-methyltyrosin and 6-hydroxydopamine), affecting the dopamine metabolism in different ways, abolished the stimulation-induced blood pressure responses. In agreement with previous findings it is concluded that motor and autonomic activation, elicited in ventral midbrain structures are mediated by catecholaminergic transmission.

Animals↗

PubMed1980

Sleep, wakefulness and the monosynaptic reflex in fetal and newborn lambs.

1. Electrocorticogram (ECoG), electromyogram (EMG) of the lateral rectus and antigravity muscles (neck and masseter) and breathing activity (FB) were monitored in chronically prepared fetal sheep of 125-140 days gestation and in newborn lambs up to 11 days postnatal age. 2. Awake state (AW), non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM) were defined using standard criteria for ECoG, eye movements and postural muscle tone. 3. The percentage of time the fetuses spent in each state was: NREM sleep 53%, REM sleep 41.4%, and AW 5.6%. 4. Spontaneous intrauterine breathing activity occurred only during REM sleep, but 35% of REM sleep was not associated with FB. 5. Gasps (isolated deep inspirations) appeared occasionally throughout the recording and were not related to any specific sleep state or wakefulness. 6. In the fetus, the monosynaptic reflex (MSR) induced by direct electrical stimulation of the fibular nerve was enhanced by about 75% during REM sleep compared to NREM and AW. In the newborn lamb the adult pattern of suppression of MSR during REM sleep was not seen until several days after birth.

Animals↗

PubMed1980

Oxygen supply of the brain cortex (rat) during severe hypoglycemia.

Oxygen supply of the brain cortex together with changes in the electrocorticogram (ECoG) were investigated during and after insulin induced hypoglycemia in 13 anaesthetized rats. Local oxygen partial pressures (pO2) on the parietal cortex were continuously measured with a multiwire surface electrode of the Clark type. During early hypoglycemia with a mean arterial glucose concentration [G]a of 2.81 (SD +/- 0.40) mmol/l, the local tissue pO2 did not change significantly as compared to the pO2 values recorded during the control period with a normal [G]a of 4.51 (SD +/- 0.70) mmol/l. During severe hypoglycemia at a [G]a of 1.39 (SD +/- 0.2) mmol/l, pO2 began to increase continuously on all 104 measuring sites, independently of changes in arterial blood pressure and ECoG. During a period of 7-18 min of isoelectricity, tissue pO2 remained elevated so long as blood pressure did not decrease. After injection of a 25% glucose solution, pO2 gradually decreased to control values within 30-60 min in most experiments. We conclude from these results that oxygen supply is generally improved during severe hypoglycemia. We assume that the increase in tissue pO2 is mainly caused by an increase in microflow. Thus, the neuronal damage occurring after severe hypoglycemia, as reported in literature, cannot primarily be caused by an oxygen deficiency.

Animals↗

PubMed1983

MAO-B inhibitor deprenyl and beta-phenylethylamine potentiate [D-ALA2]-Met-enkephalinamide-induced seizures.

The relationship between deprenyl (MAO-B inhibitor), beta-phenylethylamine (PEA, MAO-B substrate) and [D-Ala2]-Met-enkephalinamide (DALA)-induced seizure was studied in the urethane-anaesthetized rats. A combined electromyographic (EMG) and electrocorticographic (ECoG) method was used. PEA (20-100 micrograms ivt) or DALA (10 micrograms ivt) induced myoclonic contractions (MC) in the submandibular muscle and epileptiform pattern with spike activity in the ECoG. Administration of subconvulsant doses of PEA (5-10 micrograms ivt 0.5-1 min before DALA) significantly increased DALA-induced seizure activity. Similarly, blockade of MAO-B with deprenyl (3-48 mg/kg ip) also enhanced DALA-induced epileptiform pattern. It is evident from this study that MAO-B system significantly modulates the excitatory phenomena induced by DALA. These findings of interactions between MAO-B system and enkephalinergic one, might be of relevance in the clinical situations such as psychosis, stress, a use of tricyclic antidepressants and all other cases, where the alteration of MAO-B system is a part of disease or induced during drug therapy.

2-Hydroxyphenethylamine↗

PubMed1994

A phase I/II study of 4'-O-tetrahydropyranyl-doxorubicin, 5-fluorouracil, and high-dose leucovorin as first-line therapy in advanced breast cancer patients.

A total of 50 patients were treated weekly with 5-fluorouracil (FU), leucovorin (LV), and 4'-O-tetrahydropyranyl-doxorubicin (THP) as first-line chemotherapy for advanced breast cancer (ABC). In phase I the doses of LV (500 mg/m2, day 1) and FU (350 mg/m2, day 1) were held constant, while the dose of THP (day 1) was escalated, from the initial dose of 10 mg/m2 up to the maximum tolerated dose (MTD). Twenty-eight patients entered phase I, and MTD for THP was defined as 35 mg/m2 in this combination. Dose-limiting toxicities were myelosuppression and hepatotoxicity. In phase II, another 22 patients were treated with THP at a dose level of 30 mg/m2. Including 4 patients already treated at this dose in the first part, 25 patients were evaluable for response: 1 patient obtained a complete response (CR) and 13 showed a partial response (PR), giving an objective response rate of 56%. The median duration of response was 9.1+ months and median survival, 15.5+ months. Side effects were generally mild, with ECOG grade I and II leukopenia in 51% of all cycles and grade III in 3% of the courses. Other toxicity included nausea and vomiting (54% and 8%, respectively) and alopecia (24%), all restricted to ECOG grade I and II. Our results suggest that weekly THP/LV-FU represents an active regimen for first-line treatment of ABC with relative low toxicity.

Adult↗

PubMed1987

Proconflict and electrocorticographic effects of drugs modulating GABAergic neurotransmission.

Proconflict and electrocorticographic effects of drugs acting on the benzodiazepine (BDZ)/GABA/chloride-ionophore receptor complex were studied in rats in an attempt to correlate their anxiogenic and epileptogenic activities. Evidence for proconflict activity was assessed by means of an operant conflict procedure based on the simultaneous reward and punishment of a conditioned task, while epileptogenic properties were assessed by monitoring the electrocorticogram (ECoG) of free-moving rats. Pentylenetetrazole and picrotoxin, which act through a site on the chloride channel, and the benzodiazepine (BDZ) inverse agonist FG 7142 showed epileptogenic alterations in the ECoG at doses, respectively, 8, 2 and 3 times higher than those eliciting a significant proconflict effect. For the partial inverse agonist CGS 8216, a ratio of about 60 was found while the BDZ antagonist Ro 15-1788 showed neither epileptogenic nor proconflict activity, except at the highest tested dose for the latter effect (40 mg X kg-1 PO). Inhibition of GABA transmission may mediate both anxiogenic and epileptogenic actions, and a link between these properties may exist as a continuous spectrum of negative intrinsic efficacy at the central BDZ/GABA/chloride-ionophore receptor complex.

Animals↗

PubMed1992

Intraoperative monitoring by transtympanic electrocochleography and brainstem electrical response audiometry in acoustic neuroma surgery.

The preservation of hearing is a major aim of contemporary temporal bone surgery. Our present findings demonstrate that intraoperative monitoring is a key method for attaining serviceable postoperative hearing after the removal of an acoustic neuroma. Both electrocochleography (ECoG) and brainstem electrical response audiometry were performed in 96 patients operated on for acoustic neuromas. The specificity of the different monitoring methods was affected by surgical manipulations in addition to such non-specific influences as CSF drainage, core body temperature and anesthesia. In the present study ECoG was found to be more reliable in assessing the intra- and postoperative course with respect to the preservation of cochlear function.

Audiometry, Evoked Response↗

PubMed1993

Effects of GABAmimetics on electrocorticographic spike discharges induced by guanidinoethanesulfonic acid (amidino-taurine) in the rat.

The effect of guanidinoethanesulfonic acid (GES) on rat electrocorticograms (ECoG) and the effects of gamma-aminobutyric acid (GABA) and GABA-agonists on the ECoG changes induced by GES were studied. Sporadic spike discharges began 2-5 min after 1 mumol GES/10 microliters on filter paper was applied to the pia mater of the left sensorimotor cortex; spike discharges extended to the opposite cerebral hemisphere 60 min after the onset of the ipsilateral spike discharges. The spike discharges with a frequency of 5-10 spikes/min lasted until the end of the 4 hour recording. The induced spike discharges were suppressed when the original GES soaked filter paper was replaced by one containing GES (1 mumol) supplement combined with taurine (1 mumol/10 microliters). GABA (1 mumol) and its receptor agonist, muscimol (10 nmol) and (3R)-(-)-4-amino-3-hydroxybutyric acid (1 mumol) also suppressed the GES-induced spike discharges when applied topically. Diazepam (DZP) (10 mg/kg) suppressed the GES-induced spike discharges 10 min after i.p. injection, but phenobarbital (20 mg/kg) increased the frequency and voltage of spike discharges 100 min following subcutaneous administration. Intraperitoneal injection of either valproate (200 mg/kg) or phenytoin (25 mg/kg), after the completion of the spike discharges, showed no effect. These findings suggest that neurotransmission or neuromodulatory effects of taurine participate in GES-induced seizure activity, and that GABAA and DZP receptors may play a role in the mechanism that suppresses GES-induced seizures.

Action Potentials↗

PubMed1990

Phase space topography and the Lyapunov exponent of electrocorticograms in partial seizures.

Electrocorticograms (ECoG's) from 16 of 68 chronically implanted subdural electrodes, placed over the right temporal cortex in a patient with a right medial temporal focus, were analyzed using methods from nonlinear dynamics. A time series provides information about a large number of pertinent variables, which may be used to explore and characterize the system's dynamics. These variables and their evolution in time produce the phase portrait of the system. The phase spaces for each of 16 electrodes were constructed and from these the largest average Lyapunov exponents (L's), measures of chaoticity of the system (the larger the L, the more chaotic the system is), were estimated over time for every electrode before, in and after the epileptic seizure for three seizures of the same patient. The start of the seizure corresponds to a simultaneous drop in L values obtained at the electrodes nearest the focus. L values for the rest of the electrodes follow. The mean values of L for all electrodes in the postictal state are larger than the ones in the preictal state, denoting a more chaotic state postictally. The lowest values of L occur during the seizure but they are still positive denoting the presence of a chaotic attractor. Based on the procedure for the estimation of L we were able to develop a methodology for detecting prominent spikes in the ECoG. These measures (L*) calculated over a period of time (10 minutes before to 10 minutes after the seizure outburst) revealed a remarkable coherence of the abrupt transient drops of L* for the electrodes that showed the initial ictal onset. The L* values for the electrodes away from the focus exhibited less abrupt transient drops. These results indicate that the largest average Lyapunov exponent L can be useful in seizure detection as well as a discriminatory factor for focus localization in multielectrode analysis.

Brain Mapping↗

PubMedDate not supplied

Nonsynaptic effect of the electrocorticogram of the intact hemisphere on unit activity of the neuronally isolated cortex.

The nonsynaptic influence of the electrocorticogram (ECoG) of the visual area of the intact hemisphere on unit activity in the visual area and Clare-Bishop area of the isolated cortex in darkness and during diffuse illumination of the retina was investigated in acute experiments on cats immobilized with diplacin, and with the cortex of one hemisphere neuronally isolated. Changes in unit activity of tonic character were found in darkness and both tonic and phasic responses of isolated cortical units in the visual area and Clare-Bishop area were found during diffuse photic stimulation. The possibility of using the nonsynaptic influence of the ECoG of the intact brain to stimulate different regions of the neuronally isolated cortex is examined.

Afferent Pathways↗

PubMed1977

Desynchronization of electrical activity in rats induced by deprenyl--an inhibitor of monoamine oxidase B--and relationship with selective increase of dopamine and beta-phenylethylamine.

Electrophysiological and biochemical effects of deprenyl and beta-phenylethylamine were studied in rats. d,1-Deprenyl, 1-deprenyl (4-6 mg/kg) and beta-phenylethylamine (75 mg/kg) induced a desynchronization of ECOG after i.p. administration of drugs. The effects lasted several hours. The biochemical analysis indicate that d,1-deprenyl (4 mg/kg) nearly doubled the concentration of brain dopamine (DA) while the concentration of noradrenaline was not altered. The maximal increase was reached at 60 min and the enhanced concentration of DA stayed at this level up till 180 min after administration of drug. Treatment of rats with alpha-methyl-p-tyrosine (200 mg/kg) did not antagonize a deprenyl induced desynchronization of ECOG. However, even low dose of haloperidol (0.1 mg/kg) abolished the arousal effect of d,1-deprenyl and beta-phenylethylamine. It is suggested that desynchronization of EEG induced by deprenyl is more likely due to increased endogenous beta-phenylethylamine than to increased concentration of endogenous DA in the brain.

Acoustic Stimulation↗

PubMed1989

Mitoxantrone use in breast cancer patients with elevated bilirubin.

To determine the safety and efficacy of mitoxantrone use in hyperbilirubinemic breast cancer patients, a prospectively determined dosage schedule was evaluated in a multi-center trial. Pretreatment bilirubin prospectively defined three groups: Controls (with normal bilirubin) and two Study groups (with either moderate or severe bilirubin increase). Bilirubin determined initial mitoxantrone dose as well: bilirubin less than 3.5 mg/dl, 14 mg/m2; and bilirubin greater than or equal to 3.5 mg/dl, 8 mg/m2. Mitoxantrone at 14 mg/m2 was well tolerated in patients with moderate hepatic dysfunction. Patients with severe hepatic dysfunction demonstrated a mixed toxicity picture, with performance status (ECOG level 3) defining a population with limiting myelosuppression and/or early death. The survival of Study patients with severe hepatic dysfunction (median 17 days) was significantly worse than both Control (p less than 0.01) and Study (p less than 0.05) patients with lower bilirubin. Entry performance status (ECOG level 0-2 versus level 3) profoundly influenced survival (median survival 222 days versus 25 days, respectively, p less than 0.0001). Objective responses were seen in patients with both normal and elevated bilirubin. Bilirubin reduction following mitoxantrone commonly occurred, representing at least an indicator of favorable prognosis. Recommendations for mitoxantrone use include: 1. Patients with moderate bilirubinemia tolerate 14 mg/m2 mitoxantrone with reasonable chance for benefit. 2. Patients with severe hepatic dysfunction and poor performance status should not be given mitoxantrone. A definitive recommendation regarding use of reduced 8 mg/m2 mitoxantrone in patients with severe hyperbilirubinemia and favorable performance status requires further study.

Adenocarcinoma↗

PubMed1981

Electrocorticographic activity induced by gamma hydroxybutyrate in the rat during ontogenesis.

GHB at a dose of 200 mg . kg-1 i.p. elicited groups of slow waves with a frequency of 4--5 Hz in both frontal and occipital ECoG leads in adult rats. In 25- an 18-day-old rats similar slow wave activity became continuous and exhibited a clear-cut maximum in the frontal regions. In 15- and 12-day-old animals slow wave activity was also registered in the frontal region but it was organized into short groups of unstable frequency. No ECoG effects of GHB could be found in 9-day-old rats.

Aging↗

PubMed1990

Action of tianeptine on focalization of attention in cat.

Tianeptine, an antidepressant substance devoid of sedative action, was investigated for its effects on focalization of attention in cats, using combined behavioural and electrocorticographic (ECoG) observations. The ECoG index was the presence of 40 Hz frontoparietal rhythmic cortical activities, developing while the animal displayed a behaviour suggesting focused attention. Cats were observed in two conditions: a "neutral" one, with no specific target, and another one, "of focused attention" where a live mouse placed in a transparent box was present in the recording room, each test lasting for 90 min. After treatment the animals displayed increased attention even in the neutral situation, where the cat, instead of sleeping like during control sessions, payed sustained attention to its environment. Conversely, at corresponding doses, amitriptyline, another antidepressant drug chosen as a reference, induced uninterrupted slow sleep even in the situation of focused attention.

Amitriptyline↗