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At least 73 records · Page 4Linked to original sources
PubMed2000

Sensorimotor cortical influences on cuneate nucleus rhythmic activity in the anesthetized cat.

This work aimed to study whether the sensorimotor cerebral cortex spreads down its rhythmic patterns of activity to the dorsal column nuclei. Extracellular and intracellular recordings were obtained from the cuneate nucleus of chloralose-anesthetized cats. From a total of 140 neurons tested (106 cuneolemniscal), 72 showed spontaneous rhythmic activity within the slow (< 1 Hz), delta (1-4 Hz), spindle (5-15 Hz) and higher frequencies, with seven cells having the delta rhythm coupled to slow oscillations. The spindle activity recorded in the cuneate was tightly coupled to the thalamo-cortico-thalamic spindle rhythmicity. Bilateral or contralateral removal of the frontoparietal cortex abolished the cuneate slow and spindle oscillations. Oscillatory paroxysmal activity generated by fast electrical stimulation (50-100 Hz/1-2 s) of the sensorimotor cortex induced burst firing synchronized with the paroxysmal cortical "spike" on all the non-lemniscal neurons, and inhibitory responses also coincident with the cortical paroxysmal "spike" in the majority (71%) of the cuneolemniscal cells. The remaining lemniscal-projecting neurons showed bursting activity (11%) or sequences of excitation-inhibition (18%) also time-locked to the cortical paroxysmal "spike". Additionally, the cerebral cortex induced coherent oscillatory activity between thalamic ventroposterolateral and cuneate neurons. Electrolytic lesion of the pyramidal tract abolished the cortically induced effects on the contralateral cuneate nucleus, as well as on the ipsilateral medial lemniscus. The results demonstrate that the sensorimotor cortex imposes its rhythmic patterns on the cuneate nucleus through the pyramidal tract, and that the corticocuneate network can generate normal and abnormal patterns of synchronized activity, such as delta waves, spindles and spike-and-wave complexes. The cuneate neurons, however, are able to generate oscillatory activity above 1 Hz in the absence of cortical input, which implies that the cerebral cortex probably imposes its rhythmicity on the cuneate by matching the intrinsic preferred oscillatory frequency of cuneate neurons.

Animals↗
PubMed2003

Circadian rhythms in humans' delta sleep electroencephalogram.

Eight healthy young male volunteers entered a 20-40 min ultrashort sleep-wake schedule for 78 h in the time-isolation facility. Rectal temperature was continuously recorded. Sleep electroencephalograms (EEGs) obtained during 20 min nap trials were stored in the computer and later analyzed by fast Fourier transform. A two-way repeated-measures ANOVA (with day and time-of-day as the repeated measures) revealed significant circadian rhythms in the powers of sigma and delta sleep EEGs, and in rectal temperature. These results obtained under conditions in which behavioral confounding factors of retiring and rising were experimentally minimized suggest that the circadian pacemaker contributes to determining the hours of day when one can sleep deeply.

Adult↗
PubMed2004

Nonlinear analysis of EEG during NREM sleep reveals changes in functional connectivity due to natural aging.

The spatial organization of nonlinear interactions between different brain regions during the first NREM sleep stage is investigated. This is achieved via consideration of four bipolar electrode derivations, Fp1F3, Fp2F4, O1P3, O2P4, which are used to compare anterior and posterior interhemispheric interactions and left and right intrahemispheric interactions. Nonlinear interdependence is detected via application of a previously written algorithm, along with appropriately generated surrogate data sets. It is now well understood that the output of neural systems does not scale linearly with inputs received and, thus, the study of nonlinear interactions in EEG is crucial. This approach also offers significant advantages over standard linear techniques, in that the strength, direction, and topography of the interdependencies can all be calculated and considered. Previous research has linked delta activity during the first NREM sleep stage to performance on frontally activating tasks during waking hours. We demonstrate that nonlinear mechanisms are the driving force behind this delta activity. Furthermore, evidence is presented to suggest that the aging brain calls upon the right parietal region to assist the pre-frontal cortex. This is highlighted by statistically significant differences in the rates of interdependencies between the left pre-frontal cortex and the right parietal region when comparing younger subjects (<23 years) with older subjects (>60 years). This assistance has been observed in brain-imaging studies of sleep-deprived young adults, suggesting that similar mechanisms may play a role in the event of healthy aging. Additionally, the contribution to the delta rhythm via nonlinear mechanisms is observed to be greater in older subjects.

Adult↗
PubMed2005

Can an inert sleeping pill affect sleep? Effects on polysomnographic, behavioral and subjective measures.

RATIONALE: Since two recent meta-analyses on sleep changes associated with placebo in clinical trials suggested a beneficial effect of placebo treatments, pointing to a dissociation between subjective and objective measures of sleep, the current experiment was directly aimed to assess the effects of an inert compound, administered with the suggestion that it was a hypnotic substance in subjects with mild sleep complaints. OBJECTIVES: The aim of this study was to compare subjective, behavioral, polysomnographic (PSG), and quantitative electroencephalographic (EEG) changes during a night preceded or not by the intake of two 50-mg lactose capsules. METHODS: Ten female students, selected by the Pittsburgh Sleep Quality Index, slept for three consecutive nights in a sleep laboratory, with the experimental (EXP) night defined by the administration of two 50-mg lactose pills. Self-ratings of sleep quality and performance were assessed upon morning awakening of baseline (BSL) and EXP nights. RESULTS: The EXP nights were self-rated as more restful and characterized by a decreased number of nocturnal awakenings than the BSL nights. PSG measures showed that wakefulness after sleep onset significantly decreased during the EXP night as compared to the BSL night. The EXP nights also showed an increase of 0.5-4.0 Hz power during nonrapid eye movement sleep and a decrease of EEG activity in the beta frequency range during rapid eye movement sleep only at central brain sites. A specific improvement of behavioral measures was also found upon morning awakening after the EXP night compared to the BSL night. CONCLUSIONS: The administration of an inert pill improves both the subjective and objective quality of sleep. The reduced sleep fragmentation and the effects on some quantitative EEG markers of sleep homeostasis suggest that the experimental manipulation induced coherent changes in the subsequent sleep, resembling an enhancement of sleep pressure. The regional differences of EEG activity suggest the involvement of a specific physiological mechanism distinct from that of effective treatments.

Adult↗
PubMed2006

Non-convulsive status epilepticus during lithium treatment at therapeutic doses.

The purpose of this study is to report the case of a patient with normal lithium serum levels who developed non-convulsive status epilepticus (NCSE). A 52-year-old woman with bipolar disorder type I (DSM-IV) treated with lithium experienced bradypsychism and episodes of confusion and spatial disorientation without signs or symptoms of lithium intoxication. Lithium serum levels were in the normal range. A brain MR scan was negative; the electroencephalogram (EEG) revealed a background 3-4 Hz delta rhythm and diffuse spike discharges. Prompt EEG and clinical response to intravenous diazepam therapy was observed. Based on these findings, a diagnosis of NCSE was made and lithium therapy was withdrawn, resulting in symptom remission and EEG normalization. The treatment was resumed after two months to test the correlation between NCSE and lithium therapy. Resumption of therapeutic range lithium induced the same clinical symptoms and EEG patterns; the therapy was thus definitively discontinued. The present data-signalling the temporal correlation of clinical and EEG changes with drug administration and withdrawal-suggest that even in the therapeutic range lithium treatment may trigger NCSE onset in predisposed subjects.

Bipolar Disorder↗
PubMed2006

Age-related characteristics of brain development in children living in the north.

The morphofunctional age-related development of the brain was studied in schoolchildren living in the difficult climatological-geographic and socioeconomic conditions of the north (Arkhangel'sk region). Of the 62 students in country middle schools, EEG amplitude-frequency, time, and spatial measures corresponded to age norms (European norms) in only 10 cases (16%). A further 26 children (53%) showed minor abnormalities in the form of an inadequate degree of organization of the temporospatial EEG pattern, mainly in the frontal and temporal lobes of the brain, with increases in the levels of the theta and delta rhythms, and the absence of any marked "functional nucleus" in the alpha rhythm. In the remaining 14 children (29%), EEG measures showed more marked delays in mental development (DMD), which were combined with learning difficulties and abnormal behavior. The retardation in the morphofunctional development of the brain in northern children averaged 1.5-2 years, which coincides with delays in hormonal and physical development described by other authors.

Adolescent↗
PubMed1990

The sleep of dysthymic patients: a comparison with normal controls.

All-night electroencephalographic (EEG) sleep recordings were compared in dysthymic patients and normal controls. Patients were selected according to DSM-III and underwent 2 weeks of treatment with placebo before the sleep evaluation, which also included self-assessments of sleep quality. As compared with normals, dysthymic patients demonstrated fragmented and superficial sleep with no changes in rapid eye movement (REM) sleep. In addition to sleep continuity disturbances, dysthymics had a higher percentage of stage 1 and a reduction of slow wave sleep (SWS), mainly due to a diminished percentage of stage 4. Other differences were related to a higher incidence of some EEG events, and it is suggested that the analysis of sleep microstructure is a useful approach to study sleep physiology in psychiatric patients. The classification of minor forms of depression is a controversial issue and therefore the nosological implications of our findings are discussed.

Adult↗
PubMed1994

Quantified EEG in different G situations.

The electrical activity of the brain (EEG) has been recorded during parabolic flights in trained astronauts and non trained volunteers as well. The Fast Fourier analysis of the EEG activity evidenced more asymmetry between the two brain hemispheres in the subjects who suffered from motion sickness than in the others. However, such a FFT classification does not lead to a discrimination between deterministic and stochastic events. Therefore, a first attempt was made to calculate the dimensionality of "chaotic attractors" in the EEG patterns as a function of the different g-epochs of one parabola. Very preliminary results are given here.

Aerospace Medicine↗
PubMed1987

Deviations in brain development due to caloric undernutrition and scope of their prevention by rehabilitation: alterations in the power spectra of the EEG of areas of the neocortex and limbic system.

Wistar rats underwent caloric undernutrition so as to produce undernourished pups (F1, both male and female), which were put on a reduced diet throughout life, causing deficits in body weight of 40-70%, and in brain weight of 14-20% by adulthood. These chronic undernourished rats were mated and their progeny (F2), which had suffered gestational and postnatal undernutrition, were undernourished, like their parents, throughout life until the moment of use in this study. At this degree of chronic undernutrition, rats do not appear to be sick or morbid, but only small-for-age, they are active and can reproduce. The computer-generated power spectra of the EEG of two neocortical areas (visual and motor) and of 3 regions of the limbic system (cingulate, hippocampus and olfactory bulb) of the chronically undernourished pups were obtained at different ages from birth to adulthood, and compared with the normal ontogenetic patterns of corresponding areas obtained from age-matched controls. In another group of rats, the undernutrition was imposed on normal pups from the day of weaning (21st day), i.e., after the major part of the brain growth spurt is over. Finally, the effect of restituting normal rehabilitatory nutrition from the day of weaning on the chronic group was also studied. The results show that all brain regions studied were affected by the chronic caloric undernutrition. The deviations from the normal consist of: (1) an initial lag or delay in the development of the EEG amplitude and activity by several days, (2) a later development of an abnormally high amplitude or power in the EEG power spectra by about the weaning age, and (3) an imbalance in the occurrence of the characteristics of the EEG of the respective areas of the brain (the low and high frequency spindles of slow sleep, the slow and fast theta activities of paradoxical sleep of the hippocampus, the delta rhythm, etc.). While the chronic undernutrition was continuing there was also a certain degree of spontaneous reduction in the magnitude of abnormality after about 80 days of age, instead of worsening with age, perhaps due to an intrinsic adaptational readjustment to the stress of the nutritional deprivation. The results reveal a variation in the susceptibility of development to these abnormalities. Typical examples of the range of variation of the effects are presented in the results showing that there can be nearly normal EEG patterns in some undernourished subjects (about 14-22%), and also that there can be abnormal EEG power spectra in a proportion of normals (up to about 20%).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Epidemiology of absence epilepsy: EEG findings and their predictive value.

This population-based study of absence epilepsy comprised 97 children, ranging in age from newborns to 15 years. All had regular bilaterally synchronous and symmetric 2-4 Hz spike-and-slow wave discharges and absences with or without generalized tonic-clonic seizures (GTCS). Patients without GTCS tended to have long episodes of 2-4 Hz spike-and-slow wave discharges (greater than or equal to 10 sec), and simultaneous clinical correlates more frequently than those with GTCS. Posterior delta rhythm was found only in patients without GTCS. Focal abnormalities, albeit transient, were more frequent among patients with GTCS. The initial electroencephalogram was of some early predictive value in patients with only absences at the time of the initial registration. Brief episodes of 2-4 Hz spike-and-slow wave (less than 10 sec) without clinical correlates were associated with a slightly increased risk of future GTCS.

Adolescent↗
PubMed2006

Development of MEG sleep patterns and magnetic auditory evoked responses during early infancy.

OBJECTIVE: To follow the development of MEG sleep patterns and auditory evoked responses (AERs) during the first six months of life. METHODS: The subjects were 18 neonates, born at conceptional age (CA) 36-42 weeks, following uncomplicated pregnancies. During each session, several 10-min MEG recordings were acquired in the presence of auditory stimulation. The recordings were classified into three distinct MEG patterns-low amplitude irregular; high-amplitude slow; and mixed-based largely on MEG amplitude and frequency. Averaged AERs were computed for the entire recording and for each MEG pattern within the recording. The results were based on analysis of 61 recording sessions of the 10 subjects who yielded three or more sessions of usable data. RESULTS: Developmental changes in the MEG sleep patterns were most pronounced at the earliest ages. By CA 48 weeks the patterns had progressed to a more mature form, characterized by the prevalence of delta wave sleep, absence of discontinuity, and development of spindling and higher amplitude delta rhythms. In contrast to the MEG patterns, the AERs did not change markedly during the first 8 weeks (CA 40-48 weeks) and showed a simple morphology, consisting of a prominent deflection at 250 ms (P250m) and a more diffuse one at around 750 ms (N750m). During the period CA 48-54 weeks, however, a relatively abrupt transition occurred to a more complex morphology, characterized by a double peak with peak latencies 150ms (P150m) and 350 ms (P350m). Beyond this period the AERs continued to evolve, showing biphasic complexes and the emergence of late components arising from outside the auditory cortex. CONCLUSIONS: Over the age range of this study the MEG sleep patterns and AER developed in succession, rather than concurrently; i.e. development of the sleep patterns was most rapid during the first 8 weeks (CA 40-48 weeks) while major development of the AERs commenced after this time. SIGNIFICANCE: This finding suggests that the brain must achieve a certain level of overall maturity, reflected in the character of the MEG sleep patterns at CA 48 weeks, before the cortex enters a phase of significant functional development, reflected in the more rapid evolution of the AER after CA 48 weeks. The results of this study affirm the efficacy of MEG for spatiotemporal characterization of neonatal brain activity.

Acoustic Stimulation↗
PubMed2004

18FDG-PET in epilepsies of infantile onset with pharmacoresistant generalised tonic-clonic seizures.

AIMS: To investigate the pathophysiology of pharmacoresistant epilepsies with cryptogenic generalised tonic-clonic seizures (GTCS) from infancy. METHODS: 18F-Deoxy-Glucose-Positron Emission Tomography 18FDG-PET) with statistical parametric mapping (SPM). Inclusion criteria were: pharmacoresistant chronic epilepsy with GTCS commencing in infancy, no focal seizures except alternating hemiconvulsions and no focal epileptic discharges in the EEG during the first year of the disease, no focal changes upon routine neuroradiological investigations, no indication of brain damage according to history and clinical examination. RESULTS: 15 boys and 15 girls with a mean age of 6.4 years (range l-14 years) were included. All still suffered from seizures despite past treatment with a mean of five drugs. Nearly all were mentally retarded, 19 to a severe and 10 to a minor degree. Fifteen were ataxic and 11 hypotonic. The EEG in 23 showed irregular generalised spike-wave discharges. PET SPM analysis revealed bioccipital hypometabolism related to sedation. Pathological monofocal hypometabolic areas were found in three, multifocal hypometabolic areas in 22 and diffuse bilateral hypometabolism in three patients. Frontal hypometabolism correlated to the degree of mental retardation, hypotonia, and ataxia. Temporomesial hypometabolism correlated to the occurrence of obtunded states and prominent delta rhythms in the EEG. Central and parietal changes were associated with the occurrence of myoclonic seizures and spike-wave discharges. CONCLUSIONS: 18FDG-PET in many of these children with cryptogenic generalised epilepsies showed multifocal hypometabolic areas of unknown aetiology. Primary cortical microdysgenesis and secondary changes due to the severe and long-standing epilepsy must be considered. Only a minority of patients showed restricted focal hypometabolism as a possible indication for surgical treatment.

Adolescent↗
PubMed2006

Conversion from mild cognitive impairment to Alzheimer's disease is predicted by sources and coherence of brain electroencephalography rhythms.

Objective. Can quantitative electroencephalography (EEG) predict the conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD)? Methods. Sixty-nine subjects fulfilling criteria for MCI were enrolled; cortical connectivity (spectral coherence) and (low resolution brain electromagnetic tomography) sources of EEG rhythms (delta=2-4 Hz; theta=4-8 Hz; alpha 1=8-10.5 Hz; alpha 2=10.5-13 Hz: beta 1=13-20 Hz; beta 2=20-30 Hz; and gamma=30-40) were evaluated at baseline (time of MCI diagnosis) and follow up (about 14 months later). At follow-up, 45 subjects were still MCI (MCI Stable) and 24 subjects were converted to AD (MCI Converted). Results. At baseline, fronto-parietal midline coherence as well as delta (temporal), theta (parietal, occipital and temporal), and alpha 1 (central, parietal, occipital, temporal, limbic) sources were stronger in MCI Converted than stable subjects (P<0.05). Cox regression modeling showed low midline coherence and weak temporal source associated with 10% annual rate AD conversion, while this rate increased up to 40% and 60% when strong temporal delta source and high midline gamma coherence were observed respectively. Interpretation. Low-cost and diffuse computerized EEG techniques are able to statistically predict MCI to AD conversion.

Aged↗
PubMed2000

The pain inhibiting pain effect: an electrophysiological study in humans.

This study examines the counterirritation phenomenon of experimental pain in human subjects. Phasic pain induced by intracutaneous electrical stimuli was simultaneously applied with tonic pain induced by ischemic muscle work. Pain ratings, spontaneous EEG and evoked potentials were measured. We found a significant reduction of phasic pain ratings during and 10 min after tonic pain. The late somatosensory evoked potentials as neurophysiological correlates of phasic pain sensation were attenuated until 20 min after tonic pain offset. The extent of phasic pain relief due to concomitant tonic pain was small but significant, comparable to the effect of a regular systemic dose of a narco-analgesic drug in this experimental pain model. On the other hand, no modulations in the late components of the auditory evoked potential and the power spectrum of the spontaneous EEG were observed. These variables reflect the attention and vigilance of the subject and are well-known to be affected by opioids. The only exception was an increase of beta power, which might reflect hyperarousal during tonic pain. These results support the suggestion, that the analgesic effect of heterotopic noxious stimulation in humans is based on the activation of a specific inhibitory pain control system. Systemic release of endogenous opioids is unlikely to be involved, because the typical effects of opioids on the EEG were not observed.

Adult↗
PubMed1999

Validation of a right hemisphere vigilance system as measured by principal component and factor analyzed quantitative electroencephalogram.

Arruda and colleagues [Arruda, J.E., Weiler, M.D., Valentino, D.A. et al., 1996. A guide for applying principal-component analysis and confirmatory factor analysis to qEEG data. Int. J. Psychophysiol. 23, 63-81.] recently described seven neurophysiological measures that were previously derived and confirmed using factor analytic procedures and the quantitative electroencephalogram (EEG) sampled from 208 normal controls during an auditory continuous performance test (CPT). The purpose of the present investigation was to further test the validity of these empirically derived measures by examining each measure's relationship with CPT-related declines in performance. Participants were 48 right-handed men (n = 13) and women (n = 35) who reported being free of any neurological condition, birthing complications, or loss of consciousness greater than 2 min. After completing an eyes-closed resting condition, participants performed a 23-min CPT while both quantitative EEG and behavioral performance were measured at 45, 405, 765 and 1125 s into the CPT. Bipolar recordings were gathered using the International 10-20 system, from eight sites: frontal, fronto-temporal, temporal and temporal-occipital. Multivariate and follow-up univariate tests suggest the existence of a neurophysiological system located within the right temporal region that appears essential for the maintenance of a sustained attentional state. If confirmed, the further quantification of this neurocognitive system may prove useful as part of a clinical diagnostic workup.

Adolescent↗