共查询到20条相似文献,搜索用时 15 毫秒
1.
Power spectra of cortical potentials of baseline activity during interstimuli intervals (4 s; Fourier transform in the frequency band of 1-60 Hz) and short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set to facial expression. Significant differences between groups of subjects with different set rigidity were observed only at the set-testing stage. Estimation of the short-term (0.8 s) induced responses of the wavelet spectra in the group with plastic set revealed an increase in the power (in comparison with the power of background activity) of the gamma2 band (41-60 Hz) in the left hemisphere of the temporal, central and occipital areas, whereas in the group with rigid set these power spectra decreased. At the same time the power in the gamma1 band (21-40 Hz) was significantly lower (at the same level with the rigid form), indicating a discrete nature and functional selectivity in the gamma frequency band. 相似文献
2.
The dynamics of power of short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set under conditions of different loads on working memory in two groups of subjects. Subjects of the first group had to react only to facial stimuli (n = 29), whereas the second group solved an additional task loading the working memory (they had to find a target stimulus in a matrix of letters, n = 35). We estimated wavelet spectra in the occipital, temporal, central and frontal areas of both hemispheres. In both groups of subjects with the plastic form of set, the power level in the gamma2 band (41-60 Hz) was significantly higher than in subject with the rigid form. In group A at the set-testing stage, the largest increase in the gamma2 band was related to the central areas of the left hemisphere. In more complex situation (group ), the increase in power in the gamma2 and gamma1 (21-40 Hz) bands was observed in the occipital and temporal areas of both hemispheres. At the same time, the EEG power of the central areas in these gamma bands was significantly lower. In the frontal areas there were no significant differences in the dynamics of power between the subjects of both groups. 相似文献
3.
Time-frequency analysis of the electrocortical activity during maturation using wavelet transform 总被引:2,自引:0,他引:2
In this study, we introduce the wavelet transform (WT) as a method for characterizing the maturational changes in electrocortical
activity in 24 fetal lambs ranging from 110–144 days gestation (term 145 days). The WT, based on multiresolution signal decomposition,
is free of assumptions regarding the characteristics of the signal. The approximation of the electrocortical activity at resolutions
varying from 2j+1 to 2j can be extracted by decomposing the signal on a wavelet orthonormal basis of L
2(R). We performed multiresolution decomposition for four sets of parameters D
2j, where −1<j<−4. The four series WT represent the detail signal bandwidths: (1) 16–32 Hz, (2) 8–16 Hz, (3) 4–8 Hz, (4) 2–4 Hz. The data
were divided into three groups according to gestational age: 110–122 days (early), 123–135 days (middle), and 136–144 days
(late). In the early group, the power was highest in the fourth signal bandwidth, with relatively low power in the other bands.
Increase in gestational age was characterized by increased power in all four bandwidths. Comparison of the cumulative distribution
function of the power in the four wavelet bands confirmed the presence of two statistically different patterns in all three
age groups. These two patterns correspond to the visually identified patterns of HVSA (high-voltage slow activity) and LVFA
(low-voltage fast activity). The earliest development change occurred in HVSA, with progressive increase in power in the 2–8
Hz band. Later changes occurred in LVFA, with a significant increase in power in the 16–32 Hz band. The same database was
also analyzed by the short-term Fourier transform (STFT) method, the most common time-frequency analysis method. Comparison
of the results clearly show that the WT provided much better time-frequency resolution than the STFT method and was superior
in demonstrating maturational changes in electrocortical activity.
Received: 7 July 1993/Accepted in revised form: 15 November 1993 相似文献
4.
Dumenko VN Kozlov MK Kurova NS Cheremushkin EA 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2008,58(1):5-11
Prestimulus EEG power spectra from different cortical areas in frequency band 1-60 Hz were studied at a stage of formation of the cognitive set to facial expression. Diversity of individual power spectra of baseline EEGs, especially in gamma frequency band 41-60 Hz makes averaging individual spectra impossible. The authors pioneered in finding that, in prestimulus periods, EEG frequencies 41-60 Hz were of higher information value than frequencies 1-20 and 21-40 Hz. The highest power of the gamma frequencies was revealed in the frontal areas of the right hemisphere in subjects with a plastic set. In the group with a rigid set, gamma frequencies of high power prevailed in the posterotemporal and occipital areas of the left hemisphere. 相似文献
5.
Fetal electrocortical activity (ECoG) is characterized by two distinct patterns: HVSA (high voltage, slow activity) and LVFA
(low voltage, fast activity). Using the wavelet transform (WT), we recently reported that the frequency characteristics of
these two ECoG patterns undergo significant maturational changes prior to birth (Akay et al. 1994a). We now report that fetal
ECoG can also be significantly affected by pharmacological agents. In this paper, we compared the effects of two opioid drugs
(morphine and [D-Pen2, D-Pen5]enkephalin, DPDPE) on fetal ECoG, using the chronically instrumented fetal lamb model. Morphine was infused intravenously
(i.v.) at 2.5 mg/h, while DPDPE was infused into the lateral cerebroventricle (i.c.v.) at 30 μg/h. The ECoG was analyzed using
WT. We performed multiresolution decomposition for four sets of parameters D
2
j
where −1<j<−4. The four series WTs represent the detail signal bandwidths: (1) 16–32 Hz, (2) 8–16 Hz, (3) 4–8 Hz, (4) 2–4 Hz. The data
were subjected to statistical analysis using the Kolmogorov–Smirnov (KS) test. Both morphine and DPDPE resulted in a significant
increase in power in the first wavelet band, while power was reduced in the second, third and fourth wavelet bands. In addition,
both drugs resulted in a disruption of the normal cyclic pattern between the two ECoG patterns. There was a difference in
the time course of action between morphine and DPDPE. This is the first occasion in which continuous ECoG has been subjected
to rigorous statistical analysis. The results suggest that the WT-KS method is most suitable for quantitating changes in the
ECoG induced by pharmacological agents.
Received: 21 January 1994/Accepted in revised form: 15 September 1994 相似文献
6.
We investigated the interaction of β-rhythm parameters with α and θ rhythms in a paradigm of cognitive set as a response on facial expression in 35 healthy adults. Data were analyzed by means of continuous wavelet transform on the basis of “maternal” complex Morlet-wavelet in a range of 1–35 Hz. Distribution cards of the values of the wavelet-transform coefficient (WLC) module characterizing potentials amplitude were analyzed. We used indicators of the mean and maximal WLC levels. A significant interaction between β2 and α rhythms at the mean WLC level at the stage of set formation was revealed in a group with rigid set, and a correlation coefficient was 0.57. The interaction between β2 and θ rhythms at the mean WLC level (correlation coefficient was 0.74) and WLC maximum (correlation coefficient was 0.8) at the same experimental stage in the group with the flexible set was found. 相似文献
7.
The development of the resonance EEG responses of the left and right occipital areas was studied in right-handed men during
prolonged (12 or 120 s) rhythmic, photostimulation with the intensity of 0.7 J and frequencies of 6, 10, and 16 Hz. Analysis
of the EEG fine spectral structure was applied to compare the accumulated baseline EEG spectra and EEG spectra during photostimulation,
to observe the dynamics of the short-term spectra and to detect power changes in the EEG narrow spectral band sharply coincident
with the stimulation frequency. The more pronounced EEG responses to photostimulation were observed in subjects with the initially
low EEG baseline, α-rhythm. Two-minute flash trains produced a substantial increase in the EEG power within the stimulation
frequency with superposed oscillatory processes with different periods. These fluctuations are considered a reflection of
intricate interaction between the adaptive and resonance EEG responses to the presented intermittent stimulation. Under 12-s
stimulation the resonance EEG responses are steadily recorded within the first 3 s of stimulation and immediately after the
flash cessation EEG power at the stimulation frequency returns to the initial level. The resonance EEG responses were more
pronounced in the right hemisphere than in the left one, especially, at the stimulation frequencies of 6 and 16 Hz. With increasing
the stimulation frequency, the maximum of resonance EEG responses was reached earlier. Under the stimulation frequency of
6 Hz, the maximal response was recorded 9–12 s after the beginning of flashes, at the frequencies of 10 and 16 Hz, it was
recorded within 3–6 and 3 s, respectively. 相似文献
8.
Baclofen is a selective gamma-aminobutyric acid (GABA) type B agonist that may have important medicinal uses, such as in analgesics
and drug addiction treatment. In addition, evidence is accumulating that suggests GABAergic-mediated neurotransmission is
altered during aging. This study investigated whether baclofen administration (5 mg kg−1) induces differential effects on cortical electrical activity with age. Electroencephalograms (EEGs) were recorded from young
(3–4 months) and aged (15–17 months) rats, and both the absolute and relative powers in five frequency bands (delta: 2–4 Hz;
theta: 4–8 Hz; alpha: 8–12 Hz; beta: 12–20 Hz; gamma: 20–100 Hz) were analyzed. Before administration of baclofen, we found
that the EEG relative power in the beta band was higher in the aged than that in the young rats. After administration of baclofen,
there was a slower increase in the relative power in the delta band in the aged than that in the young rats. Moreover, there
was no significant difference between the two age groups in absolute power in any frequency band. These findings indicate
that baclofen treatment appears to differentially modify cortical EEG activity as a function of age. Our data further elucidate
the relationship between GABAB receptor-mediated neurotransmission and aging. 相似文献
9.
The EEG power in the β1, β2, and γ frequency bands during reading according to the method of “self-regulatory utterance” was compared in subjects reading
aloud emotionally neutral business texts related to an unknown field of activity, fiction texts with clear positive or negative
valences or personally important autobiographic texts with similar emotional valences. Two groups of subjects participated
in the study: students training to be actors (N = 22) and students with other specializations (N = 23). We observed higher values of the EEG power in the γ (30–40 Hz) and β2 (18.5–29.5 Hz) frequency bands when comparing the states during reading of emotionally positive and emotionally negative
fiction texts and personally important texts. These data are similar to our previous studies with the use of techniques that
apply internal induction of positive or negative emotions without speech, in different groups of subjects. Internal induction
of positive emotions was associated with an increase in the EEG power in these bands compared to the performance of an emotionally
neutral task, whereas induction of negative emotions resulted in a decrease in the EEG power. 相似文献
10.
Electroencephalograms (EEGs) were recorded in 19 standard derivations in 88 healthy subjects (students) in the state of rest
with eyes open and during memorization (learning) of verbal bilingual semantic pairs (the Latin and Russian languages) and
retrieval of information from memory (control). The estimates of EEG coherence in these states were compared for the following
frequency bands: θ (4–7 Hz), α1 (7–10 Hz), α2 (10–13 Hz), β1 (13–18 Hz), β2 (18–30 Hz), and γ (30–40 Hz). Compared to the state of rest, the decrease in coherence in the pairs of derivations from the
frontal and central cortical areas in all EEG frequency bands was the most pronounced for memorization, and the increase in
coherence in the interhemispheric derivation pairs of the parietal-occipital region in most of the frequency bands was the
most pronounced for retrieval. In addition, in the pairs formed by derivations from the parietal-occipital region with derivations
from the frontal and central regions, retrieval is also characterized by an increase in coherence in the β2 and γ bands along with its decrease in the low-frequency ranges. The dynamics of EEG coherence, when comparing the states
of memorization and retrieval, is more statistically significant in the interhemispheric and cross-hemispheric pairs of derivations
than in the intrahemispheric pairs. The revealed topographic specificity of the dynamics of EEG coherence owing to the change
of state is considered in terms of the notion on cognitive-specific forms of sustained goal-directed mental attention. 相似文献
11.
The subjects were divided into two groups according to the α1 and α2 spectral powers in the occipital derivations of the EEG recorded in the initial state with their eyes closed. Group I included
subjects whose α1-rhythm spectral power (7–10 Hz) was more than 70% of the total α-rhythm band power. Group II included subjects whose α2-rhythm spectral power (10–13 Hz) was more than 70% of the total α-rhythm band power. It was established that, in the tasks
requiring prediction of the subsequent result (memorizing a certain sequence of signals and its subsequent reproduction on
the monitor screen), group I subjects differed from group II subjects in fewer sequence errors and a greater number of accurate
predictions. In group II subjects, a decrease in the ϑ-band spectral power in the EEG of the central and frontal cortical
areas was observed compared to the baseline. Therefore, the EEG ϑ-rhythm power at the memorizing stage was lower in them than
in group II subjects. The results suggest that the baseline characteristics of ϑ-activity can be regarded as prognostic criteria
of similar types of activity. 相似文献
12.
The effects of morphine on the relationship between fetal EEG, breathing and blood pressure signals using fast wavelet transform 总被引:4,自引:0,他引:4
In this study, we introduce the fast wavelet transform (WT) as a method for investigating the effects of morphine on the electroencephalogram (EEG), respiratory activity and blood pressure in fetal lambs. Morphine was infused intravenously at 25 mg/h. The EEG, respiratory activity and blood pressure signals were analyzed using WT. We performed wavelet decomposition for five sets of parameters D
2j
where -1 < j 5. The five series WTs represent the detail signal bandwidths: 1, 16–32 Hz; 2, 8–16 Hz; 3, 4–8 Hz; 4, 2–4 Hz; 5, 1–2 Hz. Before injection of the high-dose morphine, power in the EEG was high in all six frequency bandwidths. The respiratory and blood pressure signals showed common frequency components with respect to time and were coincident with the low-voltage fast activity (LVFA) EEG signal. Respiratory activity was observed during only some of the LVFA periods, and was completely absent during high-voltage slow activity (HVSA) EEG. The respiratory signal showed dominant power in the fourth wavelet band, and less power in the third and fifth bands. The blood pressure signal was also characterized by dominant power in the fourth wavelet band. This power was significantly increased during periods of respiratory activity. There was a strong relationship between fetal EEG, blood pressure and breathing movements. However, the injection of high-dose morphine resulted in a disruption of the normal cyclic pattern between the two EEG states and a significant increase in power in the first wavelet band. In addition, the high-dose drug resulted in a significant increase in the power of respiratory signal in the fourth and fifth wavelet bands, while power was reduced in the third wavelet band. Breathing activity was also continuous after the drug. The high-dose morphine also caused a temporary power shift from the third wavelet band to the fourth wavelet band for the 30-min period after injection of drug. Finally, high-dose morphine completely destroyed the correlation between EEG, breathing and blood pressure signals. 相似文献
13.
Gurusamy Balakrishnan Mohammed Ibrahim Piotr J. Mak Jessica Hata James R. Kincaid Thomas G. Spiro 《Journal of biological inorganic chemistry》2009,14(5):741-750
Time-resolved resonance Raman (RR) spectra are reported for hemoglobin (Hb) tetramers, in which the α and β chains are selectively
substituted with mesoheme. The Soret absorption band shift in mesoheme relative to protoheme permits chain-selective recording
of heme RR spectra. The evolution of these spectra following HbCO photolysis shows that the geminate recombination rates and
the yields are the same for the two chains, consistent with recent results on 15N-heme isotopomer hybrids. The spectra also reveal systematic shifts in the deoxyheme ν
4 and ν
Fe–His RR bands, which are anticorrelated. These shifts are resolved for the successive intermediates in the protein structure,
which have previously been determined from time-resolved UV RR spectra. Both chains show Fe–His bond compression in the immediate
photoproduct, which relaxes during the formation of the first intermediate, Rdeoxy (0.07 μs), in which the proximal F-helix is proposed to move away from the heme. Subsequently, the Fe–His bond weakens, more
so for the α chains than for the β chains. The weakening is gradual for the β chains, but is abrupt for the α chains, coinciding
with completion of the R–T quaternary transition, at 20 μs. Since the transition from fast- to slow-rebinding Hb also occurs
at 20 μs, the drop in the α chain ν
Fe–His supports the localization of ligation restraint to tension in the Fe–His bond, at least in the α chains. The mechanism is
more complex in the β chains. 相似文献
14.
Independent component analysis (ICA) of 19-channel background EEG was performed in 111 patients with the early signs of depressive
disorders and in 526 healthy subjects. The power spectra of the independent components were compared in the depressive patients
and in healthy subjects at the eyes closed and eyes opened states. Statistically significant differences between the groups were detected in three frequency bands: θ (4–7.5 Hz), α
(7.5–14 Hz), and β (14–20 Hz). Increased θ and α activities in parietal and occipital derivations of depressive patients may
have been caused by a reduced cortical activity in the projection of these derivation. Diffuse enhancement of the β activity
may be correlated with anxiety symptoms that are pronounced in the clinical picture of depressive disorders at early stages
of the disease. ICA used to compare quantitative EEG parameters in different groups of patients and in healthy persons makes
it possible to localize the differences more accurately than the traditional analysis of EEG spectra. 相似文献
15.
Networks of synchronized fast-spiking interneurons are thought to be key elements in the generation of gamma (γ) oscillations
(30–80 Hz) in the brain. We examined how such γ-oscillatory inhibition regulates the output of a cortical pyramidal cell.
Specifically, we modeled a situation where a pyramidal cell receives inputs from γ-synchronized fast-spiking inhibitory interneurons.
This model successfully reproduced several important aspects of a recent experimental result regarding the γ-inhibitory regulation
of pyramidal cellular firing that is presumably associated with the sensation of whisker stimuli. Through an in-depth analysis
of this model system, we show that there is an obvious rhythmic gating effect of the γ-oscillated interneuron networks on
the pyramidal neuron’s signal transmission. This effect is further illustrated by the interactions of this interneuron network
and the pyramidal neuron. Prominent power in the γ frequency range can emerge provided that there are appropriate delays on
the excitatory connections and inhibitory synaptic conductance between interneurons. These results indicate that interactions
between excitation and inhibition are critical for the modulation of coherence and oscillation frequency of network activities. 相似文献
16.
Yakovlev AG Vasilieva LG Shkuropatov AY Shuvalov VA 《Biochemistry. Biokhimii?a》2011,76(10):1107-1119
Primary stage of charge separation and transfer of charges was studied in reaction centers (RCs) of point mutants LL131H and
LL131H/LM160H/FM197H of the purple bacterium Rhodobacter sphaeroides by differential absorption spectroscopy with temporal resolution of 18 fsec at 90 K. Difference absorption spectra measured
at 0–4 psec delays after excitation of dimer P at 870 nm with 30 fsec step were obtained in the spectral range of 935–1060
nm. It was found that a decay of P* due to charge separation is considerably slower in the mutant RCs in comparison with native
RCs of Rba. sphaeroides. Coherent oscillations were found in the kinetics of stimulated emission of the P* state at 940 nm. Fourier analysis of the
oscillations revealed a set of characteristic bands in the frequency range of 20–500 cm−1. The most intense band has the frequency of −30 cm−1 in RCs of mutant LL131H and in native RCs and the frequency of ∼100 cm−1 in RCs of the triple mutant. It was found that an absorption band of bacteriochlorophyll anion BA− which is registered in the difference absorption spectra of native RCs at 1020 nm is absent in the analogous spectra of the
mutants. The results are analyzed in terms of the participation of the BA molecule in the primary electron transfer in the presence of a nuclear wave packet moving along the inharmonic surface of
P* potential energy. 相似文献
17.
Near-infrared (NIR) spectroscopic analysis of noncrystalline polyols and saccharides (e.g., glycerol, sorbitol, maltitol,
glucose, sucrose, maltose) was performed at different temperatures (30–80°C) to elucidate the effect of glass transition on
molecular interaction. Transmission NIR spectra (4,000–12,000 cm−1) of the liquids and cooled-melt amorphous solids showed broad absorption bands that indicate random configuration of molecules.
Heating of the samples decreased an intermolecular hydrogen-bonding OH vibration band intensity (6,200–6,500 cm−1) with a concomitant increase in a free and intramolecular hydrogen-bonding OH group band (6,600–7,100 cm−1). Large reduction of the intermolecular hydrogen-bonding band intensity at temperatures above the glass transition (T
g) of the individual solids should explain the higher molecular mobility and lower viscosity in the rubber state. Mixing of
the polyols with a high T
g saccharide (maltose) or an inorganic salt (sodium tetraborate) shifted both the glass transition and the inflection point
of the hydrogen-bonding band intensity to higher temperatures. The implications of these results for pharmaceutical formulation
design and process monitoring (PAT) are discussed. 相似文献
18.
Jehle S Hiller M Rehbein K Diehl A Oschkinat H van Rossum BJ 《Journal of biomolecular NMR》2006,36(3):169-177
A simple spectroscopic filtering technique is presented that may aid the assignment of 13C and 15N resonances of methyl-containing amino-acids in solid-state magic-angle spinning (MAS) NMR. A filtering block that selects methyl resonances is introduced in two-dimensional (2D) 13C-homonuclear and 15N–13C heteronuclear correlation experiments. The 2D 13C–13C correlation spectra are recorded with the methyl filter implemented prior to a 13C–13C mixing step. It is shown that these methyl-filtered 13C-homonuclear correlation spectra are instrumental in the assignment of Cδ resonances of leucines by suppression of Cγ–Cδ cross peaks. Further, a methyl filter is implemented prior to a 15N–13C transferred-echo double resonance (TEDOR) exchange scheme to obtain 2D 15N–13C heteronuclear correlation spectra. These experiments provide correlations between methyl groups and backbone amides. Some of the observed sequential 15N–13C correlations form the basis for initial sequence-specific assignments of backbone signals of the outer-membrane protein G. 相似文献
19.
This paper is about how cortical recurrent interactions in primary visual cortex (V1) together with feedback from extrastriate
cortex can account for spectral peaks in the V1 local field potential (LFP). Recent studies showed that visual stimulation
enhances the γ-band (25–90 Hz) of the LFP power spectrum in macaque V1. The height and location of the γ-band peak in the LFP spectrum were correlated with visual stimulus size. Extensive spatial summation, possibly mediated by
feedback connections from extrastriate cortex and long-range horizontal connections in V1, must play a crucial role in the
size dependence of the LFP. To analyze stimulus-effects on the LFP of V1 cortex, we propose a network model for the visual
cortex that includes two populations of V1 neurons, excitatory and inhibitory, and also includes feedback to V1 from extrastriate
cortex. The neural network model for V1 was a resonant system. The model’s resonance frequency (ResF) was in the γ-band and varied up or down in frequency depending on cortical feedback. The model’s ResF shifted downward with stimulus size,
as in the real cortex, because increased size recruited more activity in extrastriate cortex and V1 thereby causing stronger
feedback. The model needed to have strong local recurrent inhibition within V1 to obtain ResFs that agree with cortical data.
Network resonance as a consequence of recurrent excitation and inhibition appears to be a likely explanation for γ-band peaks in the LFP power spectrum of the primary visual cortex. 相似文献
20.
N. A. Belova A. M. Ermakov A. V. Znobishcheva L. K. Srebnitskaya V. V. Lednev 《Biophysics》2010,55(4):623-627
The influence of extremely weak alternating magnetic fields (EW AMF) directed collinearly to the static Earth magnetic field
on the rate of regeneration of planarians and the rate of gravitropic response in the stem segments of flax has been studied.
The value of bioeffects of EW AMF is determined by the parameter γB
AC/f, where γ is the gyromagnetic ratio of the magnetic moments induced by the orbital movements of electrons in atoms, and B
AC and f correspond to magnetic induction and frequency of the alternating magnetic component. It was shown that the magnitude of
bioeffects depends on the amplitude (at fixed 1000 Hz — frequency) and frequency (at fixed 192 nT — amplitude) of the alternating
component. Maxima of bioeffects are observed at γB
AC/f = 0.9; 2.75, and minor maxima γB
AC/f = 4.5; 6.1. The bioeffects are absent at γB
AC/f =1.8, 3.8, 5.3, 6.7. The positions of the maxima and minima of bioeffects correspond to the theoretical prediction (at γ
= 14000 Hz/μT). Primary targets for the EW AMF of this type are the magnetic moments induced by the orbital movements of electrons
in atoms. 相似文献