Decrease In Relative Power Research Articles

Spectral changes in electroencephalography linked to neuroactive medications: A computational pipeline for data mining and analysis

Background and objectivesThe increasing amount of open-access medical data provides new opportunities to gain clinically relevant information without recruiting new patients. We developed an open-source computational pipeline, that utilizes the publicly available electroencephalographic (EEG) data of the Temple University Hospital to identify EEG profiles associated with the usage of neuroactive medications. It facilitates access to the data and ensures consistency in data processing and analysis, thus reducing the risk of errors and creating comparable and reproducible results. Using this pipeline, we analyze the influence of common neuroactive medications on brain activity. MethodsThe pipeline is constructed using easily controlled modules. The user defines the medications of interest and comparison groups. The data is downloaded and preprocessed, spectral features are extracted, and statistical group comparison with visualization through a topographic EEG map is performed. The pipeline is adjustable to answer a variety of research questions. Here, the effects of carbamazepine and risperidone were statistically compared with control data and with other medications from the same classes (anticonvulsants and antipsychotics). ResultsThe comparison between carbamazepine and the control group showed an increase in absolute and relative power for delta and theta, and a decrease in relative power for alpha, beta, and gamma. Compared to antiseizure medications, carbamazepine showed an increase in alpha and theta for absolute powers, and for relative powers an increase in alpha and theta, and a decrease in gamma and delta. Risperidone compared with the control group showed a decrease in absolute and relative power for alpha and beta and an increase in theta for relative power. Compared to antipsychotic medications, risperidone showed a decrease in delta for absolute powers. These results show good agreement with state-of-the-art research. The database allows to create large groups for many different medications. Additionally, it provides a collection of records labeled as “normal” after expert assessment, which is convenient for the creation of control groups. ConclusionsThe pipeline allows fast testing of different hypotheses regarding links between medications and EEG spectrum through ecological usage of readily available data. It can be utilized to make informed decisions about the design of new clinical studies.

Beta to Theta Power Ratio in Electroencephalogram Periodic Components to Discriminate Mild Cognitive Impairment and Alzheimer’s Dementia

AbstractBackgroundAlzheimer’s disease dementia (AD) and mild cognitive impairment (MCI) are often associated with abnormalities in full power spectrum of electroencephalogram (EEG), including the ratio of beta/theta. Full spectrum EEG consists of aperiodic and periodic components with the latter being better associated with cognition. We investigated whether the aperiodic and periodic power components of EEGs are disrupted differently in individuals with MCI vs. AD vs. healthy controls (HC), and whether a periodic based beta/theta ratio better differentiates the three groups than a ratio based on the full spectrum.MethodData were collected in 199 participants ‐ 44 with HC (mean (SD) age: 69.1 (5.3) years), 114 with MCI (72.3 (7.5)), and 41 with AD (75.6 (6.5)). We cleaned the data using a band‐pass filter with cut‐off frequencies 1 and 45 Hz and then independent component analysis. We then used the “fooof” toolbox to decompose the EEGs into their aperiodic and periodic components. We used the area under the receiver operating characteristic curve (AUCROC) of a logistic regression classifier to distinguish HC from MCI and AD participants, and MCI from AD participants, using beta/theta ratios based on the periodic power spectrum vs. full power spectrum.ResultThere was an increase in full spectrum powers for delta, theta, and gamma, and a decrease of relative power for beta in AD participants compared to HC and MCI participants. In contrast, there were no differences in aperiodic background EEG components among HC, MCI, and AD participants. Overall, the periodic and full spectrum comparisons among the three groups were comparable except for the periodic based analysis that showed a difference between MCI and HC in the occipital beta/theta ratio (Bonferroni corrected p = 0.036). Classifiers based on beta/theta power ratio in EEG periodic components distinguished AD from HC and MCI with high AUCROC values (0.94 and 0.83, respectively), and outperformed classifiers based on beta/theta power ratio in EEG all oscillations (0.078 and 0.67, respectively).ConclusionThis study supports an advantage of a periodic based analysis over a full EEG spectrum analysis and the use of occipital beta/theta power ratio based on periodic components as a screening tool for AD.

Microelectrode array membranes to simultaneously assess cardiac and neurological signals of xenopus laevis under chemical exposures and environmental changes

Simultaneous monitoring of electrocardiogram (ECG) and electroencephalogram (EEG) in studied animal models requires innovative engineering techniques that can capture minute physiological changes. However, this is often administered with a bulky and/or invasive system that may cause discomfort to animals and signal distortions. Here, we develop an integrated bioelectronic sensing system to provide simultaneous recordings of ECG and EEG in real-time for Xenopus laevis. The microelectrode array (MEA) membrane and the distinct anatomy of Xenopus offer noninvasive multi-modal electrophysiological monitoring with favorable spatial resolution. The system was validated under different environmental conditions, including drug exposure and temperature changes. Under the exposure of Pentylenetetrazol (PTZ), an epilepsy-inducing drug, clear ECG and EEG alterations, including frequent ictal and interictal EEG events, 30 dB average EEG amplitude elevations, abnormal ECG morphology, and heart rate changes, were observed. Furthermore, the ECG and EEG were monitored and analyzed under different temperatures. A decrease in relative power of delta band was observed when cold environment was brought about, in contrast to an increase in relative power of other higher frequency bands while the ECG remained stable. Overall, the real-time electrophysiology monitoring system using the Xenopus model holds potential for many applications in drug screening and remote environmental monitoring.

Кузовні машини для внесення твердих органічних добрив: потужність на привод робочих органів і пропускна спроможність машин

The purpose of the article was to find out the effect of the capacity of body machines for applying solid organic fertilizers on the power to drive the working bodies of these machines from the power take-off shaft of the tractor. The research methodology was based on the analysis of existing body machines for the application of solid organic fertilizers using information from manufacturers in the former Soviet Union and modern Ukraine. The generalization of the obtained information was carried out on the basis of correlation-regression analysis and with the use of standard computer programs the relative power was defined as the ratio of power consumption to machine capacity. The scope of variation of machine capacity, consumption and relative power to drive the working bodies of the studied mechanization is determined, the arithmetic mean, standard deviation and coefficients of variation of factorial and performance characteristics are calculated. The correlation coefficients between power consumption and relative power and machine capacity have positive values of 0.556 and 0.668, respectively. The correlation between power consumption and relative capacity per capacity is 0.636 and 0.875, respectively. A nonlinear relationship is possible from the analysis of the values of correlation coefficients and correlation relations between the studied performance and factorial features. The alignment of experimental values of consumption and calculated-experimental values of relative power depending on the capacity of machines for rectilinear and curvilinear functions with the calculation of R2-coefficient showed a change in consumption and relative power depending on capacity by equations of increasing exponent and decreasing hyperbole. With an increase in throughput of more than 16 kg / s, the rate of decrease in relative power slows down significantly.

Acute response of prefrontal cortex in institutionalized older adults undergoing a single exergames session.

Virtual reality-based exercise (exergames) improves cognition of the elderly but the neurophysiological effects are poorly understood. The hypothesis herein established is that an ultrafast neurophysiological adaptation occurs in prefrontal cortex of elderly after completion of a single exergames session. To reinforce the aforementioned hypothesis, individuals living in a Long-Term Care Home (LTCH) participated in the study and were randomly allocated into two groups (Virtual Reality Group, VRG, n = 5; and Active Control Group, ACG n = 5). VRG performed six exercises with exergames and ACG performed exercises with the same VRG movements but with no virtual reality. Assessment of frontal cortical activity at rest and during cognitive testing via electroencephalographic activity (EEG) was performed before and immediately after the intervention. Significant decrease in relative power of EEG (RPEEG) Beta brainwave (−29 ± 18%) in the left prefrontal cortex of VRG compared to ACG (4 ± 9%) (p = 0.007). A slight improvement on semantic fluency in VRG (ES=0.21) was noted. An ultrafast prefrontal cortical adaptation may occur as an effect of a single exergames session, causing a small improvement on cognition of institutionalized elderly.

Measurement of neurovascular coupling in human motor cortex using simultaneous transcranial Doppler and electroencephalography

Objective: Event-related desynchronization (ERD) is a relative power decrease of electroencephalogram (EEG) signals in a specific frequency band during physical motor execution, while transcranial Doppler (TCD) measures cerebral blood flow velocity. The objective of this study was to investigate the neurovascular coupling in the motor cortex by using an integrated EEG and TCD system, and to find any difference in hemodynamic responses in healthy young male and female adults. Approach: Thirty healthy volunteers, aged 20–30 years, were recruited for this study. The subjects were asked to perform a motor task for the duration of a provided visual cue. Simultaneous EEG and TCD recording was carried out using a new integrated system to detect the ERD arising from the EEG signals, and to measure the mean blood flow velocity of the left and right middle cerebral arteries from bilateral TCD signals. Main results: The results showed a significant decrease in EEG power in the mu band (7.5–12.5 Hz) during the motor task compared to the resting phase. It showed significant increase in desynchronization on the contralateral side of the motor task compared to the ipsilateral side. Mean blood flow velocity during the task phase was significantly higher in comparison with the resting phase at the contralateral side. The results also showed a significantly higher increase in the percentage of mean blood flow velocity in the contralateral side of motor task compared to the ipsilateral side. However, no significant difference in desynchronization or change of mean blood flow velocity was found between males and females. Significance: A combined TCD-EEG system successfully detects ERD and blood flow velocity in cerebral arteries, and can be used as a useful tool to study neurovascular coupling in the brain. There is no significant difference in the hemodynamic responses in healthy young males and females.

Increased susceptibility to pentylenetetrazol following survival of cerebral malaria in mice.

Malaria is considered a neglected disease and public health problem, affecting >200 million people worldwide. In the present study we used the Plasmodium berghei ANKA (PbA) model of experimental cerebral malaria (CM) in C57BL/6 mice. After rescue from CM and parasite clearance, animals were submitted to a seizure susceptibility test (45 days after infection) using a low dose of pentylenetetrazol (PTZ, 30 mg/kg) and monitored with use of behavioral and electroencephalography (EEG) methods. Mice rescued from CM presented a reduced latency to myoclonic and tonic-clonic seizures and an increased duration of tonic-clonic seizures. In addition, quantitative analysis of EEG revealed a decrease in relative power at beta frequency band in PbA-infected animals after PTZ injection. Our results suggest that CM may lead to increased susceptibility to seizures in mice.

Brain Networks Responsible for Sense of Agency: An EEG Study.

BackgroundSelf-agency (SA) is a person’s feeling that his action was generated by himself. The neural substrates of SA have been investigated in many neuroimaging studies, but the functional connectivity of identified regions has rarely been investigated. The goal of this study is to investigate the neural network related to SA.MethodsSA of hand movements was modulated with virtual reality. We examined the cortical network relating to SA modulation with electroencephalography (EEG) power spectrum and phase coherence of alpha, beta, and gamma frequency bands in 16 right-handed, healthy volunteers.ResultsIn the alpha band, significant relative power changes and phase coherence of alpha band were associated with SA modulation. The relative power decrease over the central, bilateral parietal, and right temporal regions (C4, Pz, P3, P4, T6) became larger as participants more effectively controlled the virtual hand movements. The phase coherence of the alpha band within frontal areas (F7-FP2, F7-Fz) was directly related to changes in SA. The functional connectivity was lower as the participants felt that they could control their virtual hand. In the other frequency bands, significant phase coherences were observed in the frontal (or central) to parietal, temporal, and occipital regions during SA modulation (Fz-O1, F3-O1, Cz-O1, C3-T4L in beta band; FP1-T6, FP1-O2, F7-T4L, F8-Cz in gamma band).ConclusionsOur study suggests that alpha band activity may be the main neural oscillation of SA, which suggests that the neural network within the anterior frontal area may be important in the generation of SA.

Tracking EEG changes during the exposure to hyperbaric oxygen

ObjectiveThe aim was to investigate and define possible alterations in cerebral activity during prolonged hyperbaric oxygen exposure and decompression as compared to baseline activity. MethodsThirty-two channel electroencephalography (EEG) was recorded with a Bluetooth EEG system in 11 subjects. A 20-min EEG recording was carried out under three different conditions: breathing air inside a hyperbaric chamber at sea level; breathing oxygen at a simulated depth of 18msw; breathing air at sea level after decompression. Relative EEG power was estimated in frequency ranges. ResultsDuring oxygen breathing, brain activity showed an early fast delta decrease in the posterior regions, with a synchronous and significant increase in alpha in the same regions. After decompression, the delta relative power decrease was uniformly distributed over the cerebral cortex until minute 8, and the alpha relative power was maximal in the posterior regions during the first 2min. ConclusionsThese results may be relevant for establishing a reference point in future studies on oxygen-sensitive subjects who reported problems during oxygen diving. SignificanceSignificant changes in EEG relative power suggest that it may be possible to define and recognize landmarks of oxygen-induced brain activity, which would be useful in the medical treatment of subjects reporting “oxygen-toxicity diving-related problems”.

Hyperacusis-associated pathological resting-state brain oscillations in the tinnitus brain: a hyperresponsiveness network with paradoxically inactive auditory cortex

Although hyperacusis, a hyperresponsiveness to non-noxious auditory stimuli, is a sound-evoked symptom, possible resting-state pathologic oscillations in hyperacusis brain have never been explored. By comparing 17 tinnitus participants with hyperacusis (T+H+) and 17 without hyperacusis (T+H-), we aimed to explore characteristic resting-state cortical activity of hyperacusis. The T+H+ and T+H- groups, strictly matched for all tinnitus sound characteristics to exclude tinnitus-related cortical changes, were compared using resting-state electroencephalography source-localized activity complemented by functional connectivity analyses. Correlation analysis revealed that hyperacusis questionnaire score was positively correlated with the orbitofrontal cortex (OFC) beta power, the right auditory cortex (AC) alpha1 power, and the dorsal anterior cingulate cortex (dACC) beta1 power. Compared to the T+H- group, the T+H+ group demonstrated increased beta power in the dACC and OFC, and increased alpha power in the right AC. Region of interest analyses including 17 normal controls further confirmed that these differences originated solely from relatively increased power of the T+H+ group, not from a relative power decrease of the T+H- group. Also, the T+H+ group showed increased connectivity between the OFC/dACC and the AC as compared to the T+H- group. The beta power increase in the OFC/dACC may indicate increased resting-state vigilance in tinnitus patients with hyperacusis. In addition, increased alpha power in the AC may reflect an adaptive top-down inhibition against sound stimuli probably mediated by the increased beta power of the OFC. The OFC/dACC, also frequently found to be activated in analogous diseases such as allodynia/hyperalgesia, may compose a hyperresponsiveness network.

Impaired force steadiness is associated with changes in force frequency composition in subacute stroke

We tested the hypothesis that impaired force steadiness early after stroke is associated with changes in frequency composition of the force signal during constant-force task. The power spectra and the relationship between power spectra and force variability during isometric knee extension (10%, 20%, 30%, and 50% of peak torque for 10s) were studied in the paretic and non-paretic legs of 34 stroke patients (64±14years, 8–25days post-injury) and the dominant leg of 20 controls (62±10years). Power spectrum analysis of the force signal included the median frequency, peak power frequency, relative peak power, and relative power in 0–3, 4–6, and 8–12Hz bands. Force variability, quantified by coefficient of variation (CV), was increased in patients at 3 of the 4 contraction levels (P⩽0.001). Median frequency across all force levels was decreased and the relative peak power was increased in the paretic and non-paretic legs compared to controls (P⩽0.001). The relative power was increased in 0–3Hz band and decreased in both 4–6 and 8–12Hz bands in the paretic leg only (P⩽0.001). Progressively stronger contractions brought about a significant decrease in relative power in the 0–3Hz band and increase in 8–12Hz band in controls but not in stroke subjects. The hypothesis was confirmed by significant non-linear correlations between CV and each relative spectral power found in the paretic leg at most contraction levels (0.22⩽R2⩽0.72, P⩽0.0004) and in the non-paretic leg at 10% only (0.35⩽R2⩽0.52, P⩽0.0002), but not in controls. Fugl-Meyer lower extremity motor and sensory scores were not related to the frequency measures in stroke subjects (P>0.05). Limited modulation of frequency spectra and the emergence of non-linear relation between power spectra and force variability suggest that less broadband force output may account in part for impaired force steadiness in paretic and non-paretic legs early after stroke.

Ethosuximide Reduces Ethanol Withdrawal–Mediated Disruptions in Sleep‐Related EEG Patterns

Chronic ethanol (EtOH) leads to disruptions in resting electroencephalogram (EEG) activity and in sleep patterns that can persist into the withdrawal period. These disruptions have been suggested to be predictors of relapse. The thalamus is a key structure involved in both normal brain oscillations, such as sleep-related oscillations, and abnormal rhythms found in disorders such as epilepsy and Parkinson's disease. Previously, we have shown progressive changes in mouse thalamic T-type Ca channels during chronic intermittent EtOH exposures that occurred in parallel with alterations in theta (4 to 8 Hz) EEG patterns. Two groups of 8-week-old male C57BL/6 mice were implanted with wireless EEG/electromyogram (EMG) telemetry and subjected to 4 weeks of chronic, intermittent EtOH vapor exposure and withdrawal. During the week after the final withdrawal, mice were administered ethosuximide (ETX; 200 mg/kg) or saline. EEG data were analyzed via discrete Fourier transform, and sleep-scored for further analysis. Chronic intermittent EtOH exposure produced changes in the diurnal rhythms of the delta (0.5 to 4 Hz) and theta bands that persisted into a subsequent week of sustained withdrawal. These disruptions were restored with the T-channel blocker ETX. Repeated EtOH exposures preferentially increased the relative proportion of lower frequency power (delta and theta), whereas higher frequencies (8 to 24 Hz) were decreased. The EtOH-induced decreases in relative power for the higher frequencies continued into the sustained withdrawal week for both groups. Increases in absolute delta and theta power were observed in averaged nonrapid eye movement and rapid eye movement sleep spectral data during withdrawal in ETX-treated animals, suggesting increased sleep intensity. These results suggest that persistent alterations in delta and theta EEG rhythms during withdrawal from chronic intermittent EtOH exposure can be ameliorated with ETX and that this treatment might also increase sleep intensity during withdrawal.

Disturbed oscillatory brain dynamics in subcortical ischemic vascular dementia

BackgroundWhite matter hyperintensities (WMH) can lead to dementia but the underlying physiological mechanisms are unclear. We compared relative oscillatory power from electroencephalographic studies (EEGs) of 17 patients with subcortical ischemic vascular dementia, based on extensive white matter hyperintensities (SIVD-WMH) with 17 controls to investigate physiological changes underlying this diagnosis.ResultsDifferences between the groups were large, with a decrease of relative power of fast activity in patients (alpha power 0.25 ± 0.12 versus 0.38 ± 0.13, p = 0.01; beta power 0.08 ± 0.04 versus 0.19 ± 0.07; p<0.001) and an increase in relative powers of slow activity in patients (theta power 0.32 ± 0.11 versus 0.14 ± 0.09; p<0.001 and delta power 0.31 ± 0.14 versus 0.23 ± 0.09; p<0.05). Lower relative beta power was related to worse cognitive performance in a linear regression analysis (standardized beta = 0.67, p<0.01).ConclusionsThis pattern of disturbance in oscillatory brain activity indicate loss of connections between neurons, providing a first step in the understanding of cognitive dysfunction in SIVD-WMH.

Changes in spectral measures of brain electrical activity in rats after transection of the sciatic nerve

Electrophysiological measures of brain electrical activity were studied in rats during the development of neurogenic pain syndrome induced by transection of the sciatic nerve. At the peak of development of pain syndrome, three weeks after deafferentation, rearrangements in the spectra of electrical activity were seen in the limbic structures of the brain (hippocampus, amygdala, nucleus accumbens), in the frontal areas of the neocortex, and in the caudate-putamen complex: changes consisted of increases in the relative power of the delta and alpha ranges as compared with controls, along with a decrease in relative power in the beta-2 range. Changes in spectral measures of electrical activity in the limbic structures of the brain occurred independently of the clinical manifestations of neurogenic pain syndrome (autotomy). The increase in relative power in the alpha range of the spectrum of electrical activity in all the structures studied suggests that the reticular nucleus of the thalamus is involved in the pathogenetic mechanisms of neurogenic pain syndrome.

Changes in Brain Function during Administration of Venlafaxine or Placebo to Normal Subjects

Previous research has demonstrated neurophysiologic effects of antidepressants in depressed subjects. We evaluated neurophysiologic effects of venlafaxine in normal subjects. Healthy adults (n=32) received a 1-week placebo lead-in followed by 4 weeks randomized double-blind treatment with venlafaxine IR 150 mg. (n = 17) or placebo (n = 15). Brain function was examined using quantitative electroencephalographic (QEEG) power and theta cordance. Normal subjects receiving venlafaxine showed a decrease in theta-band cordance in the midline-and-right-frontal (MRF) region at 48 hours and at 1 week after randomization. Decreases in relative power also were seen in the MRF region; there were no significant changes in absolute power. These changes were significantly different from those in subjects receiving placebo. Changes in MRF cordance accurately identified treatment condition at 48 hours in 81.3% of subjects, and relative power from this region identified 60.7% of subjects. In conclusion, cordance may detect the pharmacological effects of antidepressant medication in normal subjects. Future studies should examine other classes of medication, as well as antidepressants with other mechanisms of action, to determine if cordance detects antidepressant medication effects in general in normal subjects.

The influence of bromazepam on cortical power distribution

The EEG has been widely employed in the assessment of electrophysiological changes induced by distinct medications. Its sensibility in detecting alterations produced by a specific substance may be enhanced by methods of quantitative analyses (qEEG). The present study aimed at investigating the modulatory effects of bromazepam on brain dynamics. The effects of bromazepam (3 mg) on EEG power distribution were tested in 10 healthy individuals, in a double-blind experiment. The electrophysiological measure was analyzed across experimental conditions, moments, and electrodes, in the delta, theta, alpha and beta frequency bands separately. A significant decrease of relative power was observed in delta and theta (main effect of condition). No interactions were observed. Although the expected anxiolytic EEG profile was not observed (increased beta and decreased alpha activity), this specific result may be related to other factors such as dosage used and the subjects' general physiological state, and not necessarily to the drug itself.

The influence of low-grade glioma on resting state oscillatory brain activity: a magnetoencephalography study

Purpose In the present MEG-study, power spectral analysis of oscillatory brain activity was used to compare resting state brain activity in both low-grade glioma (LGG) patients and healthy controls. We hypothesized that LGG patients show local as well as diffuse slowing of resting state brain activity compared to healthy controls and that particularly global slowing correlates with neurocognitive dysfunction. Patient and methods Resting state MEG recordings were obtained from 17 LGG patients and 17 age-, sex-, and education-matched healthy controls. Relative spectral power was calculated in the delta, theta, upper and lower alpha, beta, and gamma frequency band. A battery of standardized neurocognitive tests measuring 6 neurocognitive domains was administered. Results LGG patients showed a slowing of the resting state brain activity when compared to healthy controls. Decrease in relative power was mainly found in the gamma frequency band in the bilateral frontocentral MEG regions, whereas an increase in relative power was found in the theta frequency band in the left parietal region. An increase of the relative power in the theta and lower alpha band correlated with impaired executive functioning, information processing, and working memory. Conclusion LGG patients are characterized by global slowing of their resting state brain activity and this slowing phenomenon correlates with the observed neurocognitive deficits.

Correlations between acetylcholinesterase inhibition, acetylcholine levels and EEG changes during perfusion with neostigmine and N 6-cyclopentyladenosine in rat brain

Organophosphate poisoning can result in seizures and subsequent neuropathology. In order to improve treatment strategies in organophosphate intoxication, the relationship between acetylcholinesterase inhibition, extracellular levels of acetylcholine, and electroencephalogram (EEG) changes was investigated during local perfusion of the reversible acetylcholinesterase inhibitor neostigmine in the hippocampus and striatum of freely moving rats. Acetylcholinesterase activity and acetylcholine levels were measured by microdialysis, and EEG signals were recorded from an electrode placed near the microdialysis probe. A non-linear relationship between the acetylcholinesterase activity and the extracellular amount of acetylcholine was found, the latter being approximately three times higher in the striatum than in the hippocampus upon infusion with 10 − 4 M neostigmine. Highly accumulated extracellular acetylcholine significantly correlated with significant relative power increases of the EEG-γ 2-band and a significant relative power decrease in the β 2-band. Co-infusion of the adenosine A 1 agonist N 6-cyclopentyladenosine partly prevented acetylcholine accumulation, rendered both powers towards control values, and abolished the acetylcholine–EEG correlation. In view of the latter relationship, it is concluded that prevention of acetylcholine accumulation as a concept for neuroprotection in case of organophosphate poisoning, is worth to be further investigated.

EEG spectral analysis in children with febrile delirium

Febrile delirium is defined as an acute and transient confusional state with high fever. There are very few reports on febrile delirium, although fever is one of the commonest symptoms in children. We previously found a posterior slowing in the electroencephalogram (EEG) of delirious patients with fever. The purpose of this study is to evaluate the features of occipital slow waves by spectral analysis and to find a parameter associated with clinical improvement. Methods: Digital EEG tracings were investigated by Fourier analysis in 20 patients aged from 2 to 13 years. The fast Fourier transform (FFT) was computed for 20 s tracing from the P3-A1 and P4-A2 derivations. The spectral analysis of EEG was repeated in 7 patients. The tracings of 34 control subjects were also analyzed by FFT. EEG of a febrile, nine-year-old girl without delirium was also studied. Results: Febrile delirium was seen during the first three days of fever. The episodes lasted up to 10 min. Four patients showed febrile delirium again after admission but they became conscious a few minutes later. The relative power in the delta frequency band was increased in 65% of patients with preservation of the occipital alpha rhythm. In addition, repeated febrile delirium did not cause worsening of the posterior slowing. The duration of abnormal EEG was only a few days and the decrease of relative power in the delta frequency band was the best parameter of clinical improvement. Posterior slowing was also found in a febrile patient without delirium. Conclusion: Febrile delirious children showed the characteristic clinical and spectral analytical features and the numerical data of EEG facilitate the comparison of the serial findings.

Selective agonists of metabotropic glutamate receptors elicit significant EEG effects when infused in the nucleus accumbens of rats

The effect of intra-accumbens infusion of selective group I (( S)-3,5-dihydroxyphenylglycine, DHPG), group II ((2 S,3 S,4 S)-CCG/(2 S,1′ S,2′ S)-2-(carboxycyclopropyl)glycine, l-CCG-I) and group III (( l-(+)-2-amino-4-phosphonobutyric acid, l-AP4) metabotropic glutamate (mGlu) receptor agonists was studied in male Wistar rats. A computerised electroencephalographic (EEG) power spectral analysis was performed. While DHPG (400 nmoles) induced EEG and behavioural limbic seizures, l-CCG-I (400 nmoles) and l-AP4 (800 nmoles) induced a `depressant' EEG with an increase in relative power in the slow-frequency bands and a decrease in relative power in the high-frequency bands) and behavioural effects. These results show for the first time that the stimulation of groups I, II and III mGlu receptors located in the nucleus accumbens significantly influences the EEG tracing in rats.