EEG correlates of hypnotic susceptibility based upon fast Fourier power spectral analysis

The purpose of the present study was to determine if there were differences between high and low hypnotic susceptible subjects based upon fast Fourier power spectral analysis of the EEG recorded both before and during hypnotic tasks from frontal-temporal and occipital-parietal locations. Significant differences were obtained based upon EEG recording electrode location, EEG frequency within six different frequency domains, and hypnotic tasks. However, no main effect differences were obtained based upon hypnotic susceptibility. In contrast to some evoked potential studies in which a few differences have been obtained based on hypnotic susceptibility the lack of any EEG differences in this study even when positive and negative hallucination tasks were employed may have implications for the role of the neocortex in mediating hypnotic phenomena.     

Correlation of EEG asymmetry and hypnotic susceptibility

Hypnosis research of the last decades confirmed that some cortical regions show characteristic modification of spontaneous brain electrical activity as a function of hypnotic responsiveness. Using FFT spectrum of 16 channel EEG recording, it was demonstrated that in highly susceptible subjects the right parieto-temporal region show more electric power than the left one while the low susceptibles have left side predominance or equilibrated power in all derivations. If a specific (Ericksonian) indirect hypnosis induction was administered, the same right side preponderance could be recorded in low susceptibles, too. On the basis of these results we can confirm the importance of the right parieto-temporal associative area in the alteration of consciousness characterizing hypnotic state.     

Fourier analysis of broad spectral EEG from a fluctuation point of view

It is believed that the EEG is the most reliable method of evaluating brain function, but neither quantitative nor qualitative studies of the EEG have been carried out over the entire range of frequencies. Analysis of limited frequency bands of the EEG has not disclosed the whole of neuronal activity. The aim of this study is to clarify the upper limit of EEG frequency. Our EEG analytic system is composed of a high fiedlity preamplifier and signal processor with a frequency response within -3 dB below 20 kHz. Thirty adult cats were used for these experiments. The upper limit of the frequency varied in different structures: 6.9 +/- 0.8 kHz (+/- SEM) in motor cortex, 4.1 +/- 0.3 kHz in the hippocampus, 2.9 +/- 0.5 kHz in the amygdala, 9.3 +/- 0.6 kHz in the ventrolateral nucleus of the thalamus, and 9.9 +/- 0.5 kHz in the midbrain reticular formation. Three different types of amplitude spectra were characterized in bilogarithmic graphs. These types are named types f, f + L, and L corresponding to 1/f or Lorentzian fluctuation. In conclusion, the upper limit of frequency and the spectral types correspond to the neuronal specificity of different brain regions. Their physioanatomic significance is discussed.     

The relationship between short-term memory capacity and EEG power spectral density

Multiplying memory span by mental speed, we obtain the information entropy of short-term memory capacity, which is rate-limiting for cognitive functions and corresponds with EEG power spectral density. The number of EEG harmonics (n = 1, 2,, 9) is identical with memory span, and the eigenvalues of the EEG impulse response are represented by the zero-crossings up to the convolved fundamental, the P300. In analogy to quantum mechanics the brain seems to be an ideal detector simply measuring the energy of wave forms. No matter what the stimulus is and how the brain behaves, the metric of signal and memory can always be understood as a superposition of n states of different energy and their eigenvalues.     

EEG spectral power of young schoolchildren with perinatal pathology of the CNS

The influence of perinatal risk factors (prematurity and hypoxia) on the spectral power values of individual EEG frequency bands (θ₁, θ₂, α₁, α₂, β₁, β₂, and γ) in the state of quiet wakefulness in young schoolchildren with educational problems was studied. The results of statistical analysis showed a significant predominance of the power in the θ₁ (especially in the anterior and posterior associative areas), β, and γ (on the whole surface of the cortex, with a predominance of differences in the anterior associative areas) bands in children with a gestational age (GA) less than 38 weeks at birth compared to that in the control group (a GA of 38 weeks). The intergroup differences in the power of most frequency bands were most pronounced in the left temporal area. A relationship between the consequences of perinatal hypoxia and the GA, namely, an increase in the power (especially in the left-hemispheric areas) of all the EEG frequency components (except α₂) in the group with a GA less than 38 weeks, in contrast to its slight inhibition in the control group (except the γ band), was found. The genesis of the specific features of the pattern of local EEG synchronization, as well as their functional significance in the formation of different structures of cognitive disorders in children with perinatal dysontogenesis, is discussed.     

Assessing a learning process with functional ANOVA estimators of EEG power spectral densities

We propose to assess the process of learning a task using electroencephalographic (EEG) measurements. In particular, we quantify changes in brain activity associated to the progression of the learning experience through the functional analysis-of-variances (FANOVA) estimators of the EEG power spectral density (PSD). Such functional estimators provide a sense of the effect of training in the EEG dynamics. For that purpose, we implemented an experiment to monitor the process of learning to type using the Colemak keyboard layout during a twelve-lessons training. Hence, our aim is to identify statistically significant changes in PSD of various EEG rhythms at different stages and difficulty levels of the learning process. Those changes are taken into account only when a probabilistic measure of the cognitive state ensures the high engagement of the volunteer to the training. Based on this, a series of statistical tests are performed in order to determine the personalized frequencies and sensors at which changes in PSD occur, then the FANOVA estimates are computed and analyzed. Our experimental results showed a significant decrease in the power of \(\beta\) and \(\gamma\) rhythms for ten volunteers during the learning process, and such decrease happens regardless of the difficulty of the lesson. These results are in agreement with previous reports of changes in PSD being associated to feature binding and memory encoding.     

Relations between anxiolytic effects of diazepam and changes in the EEG spectral power

The influence of diazepam (1; 5; 10 mg/kg, i. p.), chlorpromazine (1 mg/kg) and amphetamine (1; 5 mg/kg) on the Fourier's spectral EEG power of sensomotor cortex and dorsal hippocampus and conflict behavior freely moving albino and cotton (Sigmondon hispidus) rats was studied. Effects of diazepam (5 mg/kg) in cotton rats were similar, but influence on the theta-activity was more expressed. Correlation between slowing of theta-activity and extent of anxiolytic effect in conflict situation was showed. On the basis of the results obtained the authors discuss possible mutual relations between the influence of diazepam on EEG and anxiolytic effect of benzodiazepines.     

Electrographic correlates of real and imaginary movements: spectral analysis

The research carried out with eight virtually healthy volunteers showed that movements were associated with the increased level of activation, primarily, in the central areas of the brain cortex, which was expressed in a reduction of the spectral power of alpha end beta frequencies and increase in the power of the gamma oscillations more expressed in the parietooccipital derivations of the left hemisphere. Mental reproduction of similar movements was accompanied by additional activation in the frontal, temporal, parietal, and occipitals regions and more pronounced increase in the power of the gamma oscillations. A number of electrographic phenomena associated with specific features of the movements were revealed.     

功率谱熵在痫性发作大鼠脑电检测中的应用研究

目的:研究功率谱熵在痫性发作大鼠脑电检测中的应用。方法:采用青霉素在大鼠海马微注射制备急性痫性发作模型,以深部电极记录大鼠原始脑电信号,将24只SD大鼠随机分成四组,即正常组(A),对照组(B),单电极组(C),多电极组(D)。C、D组大鼠经致痫后观察未发作期、发作前期、发作期和发作后期四期脑电信号的变化,运用谱熵对四期脑电信号进行分析,并与A、B组进行对比。结果:C组和D组脑电功率谱熵显示两组发作期与未发作期、发作前期、发作后期比较有显著差异(P0.05),发作期明显低于其它各期;未发作期和发作前期相比有明显差异(P0.05),发作前期较未发作期降低;将D组大鼠海马致痫灶(a)及其同侧附近(b)、对侧(c)三点发作各期脑电功率谱熵进行对比分析,发作前期和发作期a、b、c三点比较有明显差异(P0.05),a点最低,c点的功率谱熵值最高。结论:功率谱熵可以预报痫性发作并可对癫痫病灶的定位提供一定的帮助。     

EEG correlates of social creativity

EEG correlates of social creativity defined as ability to originally and flexibly interpret social significant situations were studied. It was found that the alpha2 and gamma2 rhythms are specific bands which make it possible to tell the difference between social creativity and control task. Solving socially significant problems in experimental conditions is accompanied by an increase in the power of the delta and gamma2 bands and desynchronization in the alpha2 band less pronounced in divergent tasks than during the interpretation of convergent visual stimuli.     

Fractal analysis of knee-joint vibroarthrographic signals via power spectral analysis

Parameters useful for the diagnosis of pathological processes leading to the deterioration of the articular cartilage surfaces of knee joints, such as osteoarthritis, may be derived from vibroarthrographic (VAG) signals. In the present work, we explore fractal analysis to parameterize the temporal and spectral variability of normal and abnormal VAG signals. The power spectrum analysis method was used with the 1/f model to derive estimates of the fractal dimension (FD). Classification accuracy of up to 0.74 was obtained with a single FD parameter, in terms of the area under the receiver operating characteristic curve (A_z), with a database of 89 VAG signals. Combinations of the features derived in the present work with other features we have reported upon recently, when used with several neural networks with radial basis functions, resulted in A_z values in the range [0.92, 0.96], with an exceptional case of perfect classification with A_z = 1.0. The proposed methods could help in the detection and monitoring of knee-joint pathology.     

Mu-delta opioid interactions. II: Beta-FNA inhibits DPDPE-induced increases in morphine EEG and EEG spectral power.

In the present study, the effects of beta-FNA on DPDPE-induced increases in morphine EEG and EEG power spectra were assessed. Adult female Sprague-Dawley rats were implanted with cortical EEG electrodes and permanent indwelling ICV and IV cannulae. Rats were administered ICV beta-FNA at 20 nmol or ICV sterile water. Then 18-24 h later, rats were administered ICV DPDPE at 2.5 nmol or ICV sterile water followed, 10 min later, by IV morphine at 3 mg/kg. Morphine-induced changes in EEG global (1-50 Hz) spectral parameters, the duration of morphine-induced high voltage EEG bursts, the period of EEG and behavioral excitation, and the latency to onset of slow-wave sleep were statistically analyzed using a one-way analysis of variance. beta-FNA pretreatment significantly decreased morphine-induced total spectral power seen in the DPDPE + morphine group. beta-FNA pretreatment also significantly decreased the duration of morphine-induced EEG bursts, the period of EEG and behavioral excitation, and the latency to onset of slow-wave sleep in the DPDPE + morphine group. These data, therefore, suggest that DPDPE may be increasing the effects of morphine on EEG through delta opioid receptors associated with the mu-delta opioid receptor complex.     

Adenosine deaminase polymorphism affects sleep EEG spectral power in a large epidemiological sample

Slow wave oscillations in the electroencephalogram (EEG) during sleep may reflect both sleep need and intensity, which are implied in homeostatic regulation. Adenosine is strongly implicated in sleep homeostasis, and a single nucleotide polymorphism in the adenosine deaminase gene (ADA G22A) has been associated with deeper and more efficient sleep. The present study verified the association between the ADA G22A polymorphism and changes in sleep EEG spectral power (from C3-A2, C4-A1, O1-A2, and O2-A1 derivations) in the Epidemiologic Sleep Study (EPISONO) sample from São Paulo, Brazil. Eight-hundred individuals were subjected to full-night polysomnography and ADA G22A genotyping. Spectral analysis of the EEG was carried out in all individuals using fast Fourier transformation of the signals from each EEG electrode. The genotype groups were compared in the whole sample and in a subsample of 120 individuals matched according to ADA genotype for age, gender, body mass index, caffeine intake status, presence of sleep disturbance, and sleep-disturbing medication. When compared with homozygous GG genotype carriers, A allele carriers showed higher delta spectral power in Stage 1 and Stages 3+4 of sleep, and increased theta spectral power in Stages 1, 2 and REM sleep. These changes were seen both in the whole sample and in the matched subset. The higher EEG spectral power indicates that the sleep of individuals carrying the A allele may be more intense. Therefore, this polymorphism may be an important source of variation in sleep homeostasis in humans, through modulation of specific components of the sleep EEG.     

Sleep EEG spectral analysis in a diurnal rodent:Eutamias sibiricus

1. Sleep was studied in the diurnal rodent Eutamias sibiricus, chronically implanted with EEG and EMG electrodes. Analysis of the distribution of wakefulness, nonrapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep over the 24 h period (LD 12:12) showed that total sleep time was 27.5% of recording time during the 12 h light period and 74.4% during the 12 h dark period. Spectral analysis of the sleep EEG revealed a progressive decay in delta power density in NREM sleep during darkness. Power density of the higher frequencies increased at the end of darkness. Power density of the higher frequencies decreased and that of the lower frequencies increased during light. 2. Analysis of the distribution of vigilance states under three different photoperiods (LD 18:6; 12:12; 6:18) revealed that changes in daylength mainly resulted in a redistribution of sleep and wakefulness over light and darkness. Under long days the percentage of sleep during light was enhanced. The time course of delta power density in NREM sleep was characterized by a long rising part and a short falling part under long days, while a reversed picture emerged under short days. As a consequence, the power density during days. As a consequence, the power density during light was relatively high under long days. 3. After 24 h sleep deprivation by forced activity, no significant changes in the percentages of wakefulness and NREM were observed, whereas REM sleep was slightly enhanced. EEG power density, however, was significantly increased by ca. 50% in the 1.25-10.0 Hz range in the first 3 h of recovery sleep. This increase gradually decayed over the recovery night. 4. The same 24 h sleep deprivation technique led to a ca. 25% increase in oxygen consumption during recovery nights. While the results of the EEG spectral analysis are compatible with the hypothesis that delta power density reflects the 'intensity' of NREM sleep as enhanced by prior wakefulness and reduced by prior sleep, such enhanced sleep depth after sleep deprivation is not associated with reduced energy expenditure as might be anticipated by some energy conservation hypotheses on sleep function.     

Spreading depression in a waking rabbit with the spectral EEG analysis

It was shown that the manifestation of the SD phenomenon in dynamics of the cortical high-frequency gamma activity is rather prominent after bipolar interpretation of the common reference electrode derivations, i.e. when the modeling of the bipolar signal on the base of monopolar EEG recordings is used. The SD wave was accompanied by significant decrease in the power of the EEG gamma band (37-47 Hz) in all observed cortical areas. A curve of decline of gamma activity power had distinct fore and back fronts, so the time of SD appearance in different cortex areas and it's spread succession could be well determined. In the long-term experiments SD waves were characterized by normal (i.e. successive) spread through the cortex mainly in initial three-four experiments. In the subsequent tests latency of SD waves in different cortex areas changed and disturbance of propagation became obvious. Sometimes SD arose rapidly (due 0.5-2 min) on the whole dorsal neocortical surface, when the standard injection of the KCI was done. In the most of experiments the delay of the SD wave appearance was prolonged till 6-9 min or no SD wave occur at some cortical regions. Week epileptiform activity could conduct abnormalities in the SD. In many instances electrophysiological signs of the cortical excitability changes were absent. However the modified spatial SD characteristic and spontaneous occurrence of the repeated. SD waves indicated the increased functional inhomogeneities of the neighboring cortical areas. So, spectral EEG analysis in awake rabbits made it possible to characterize the SD wave both in case of its normal propagation through the cortex and in unusual forms of this reaction.