Frequency modulation of theta volleys of septal neurons during rhythmic oligosynaptic stimulation in the rabbit

Activity of the neurones with stable theta-bursts was recorded extracellularly in intact and hippocampectomized septum of unanaesthetized chronic rabbits during low-frequency (3-17 Hz) stimulation of horizontal limb of the diagonal band or the lateral septal nucleus. Gradual entrainment and phase-locking of the spontaneous theta-cycles occurred. Two types of entrainment were observed: "entrainment by pause", where interburst interval was reset by the stimuli; and "entrainment by burst", where bursts were time-locked to the stimuli. Such reorganization of the spontaneous bursts occurred in a narrow frequency range of stimulation (from 4 Hz up to 9-12 Hz), with the best resonance following in the range of "basic" theta frequencies of the awake rabbit (5-6 Hz). With stimulation beyond the theta-range three phenomena occurred: shift of the burst frequencies to higher or lower harmonics of stimulation frequencies; complex interactions of basic background frequency with the rhythm of stimulation ("beating"); escape from the influence of the stimuli with return to background theta-burst frequency.     

Differential pattern of spinal sympathetic outflow in response to stimulation of the caudal medullary raphe

In urethan-anesthetized cats, frequency domain analysis was used to explore the mechanisms of differential responses of inferior cardiac (CN), vertebral (VN), and renal (RN) sympathetic nerves to electrical stimulation of a discrete region of the medullary raphe (0-2 mm caudal to the obex). Raphe stimulation in baroreceptor-denervated cats at frequencies (7-12 Hz) that entrained the 10-Hz rhythm in nerve activity decreased CN and RN activities but increased VN activity. The reductions in CN and RN discharges were associated with decreased low-frequency (相似文献   

Prestimulus EEG gamma frequencies during formation of a cognitive set to facial expression

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.     

The F1-F2 vowel chart for Czech whispered vowels a, e, i, o, u

Aim: The aim of this contribution is to present the formant chart of the Czech vowels a, e, i, o, u and show that this can be achieved by means of digital methods of sound processing. Method: A group of 35 Czech students of the Pedagogical Faculty of Palacky University was tested and a record of whispered vowels was taken from each of them. The record was digitalized and processed by the Discrete Fourier Trasform. The result is the power spectrum of the individual vocals - the graphic output consists of a plot of the relative power of individual frequencies in the original sound. The values of the first two maxima which represent the first and the second formants were determined from the graph. The values were plotted on a formant chart. Results: Altogether, 175 spectral analyses of individual vowels were performed. In the resulting power spectrum, the first and the second formant frequencies were identified. The first formant was plotted against the second one and pure vocal formant regions were identified. Conclusion: Frequency bands for the Czech vowel "a" were circumscribed between 850 and 1150 Hz for first formant (F1) and between 1200 and 2000 Hz for second formant (F2). Similarly, borders of frequency band for vowel "e" they were 700 and 950 Hz for F1 and 1700 and 3000 Hz for F2. For vowel "i" 300 and 450 Hz for F1 and 2000 and 3600 Hz for F2, for vowel "o" 600 and 800 Hz for F1 and 600 and 1400 Hz for F2, for vowel "u" 100 and 400 Hz for F1 and 400 and 1200 Hz for F2. Discussion: At low frequencies it is feasible to invoke the source-filter model of voice production and associate vowel identity with frequencies of the first two formants in the voice spectrum. On the other hand, subject to intonation, singing or other forms of exposed voice (such as emotional speech, focused speech), the formant regions tend to spread. In spectral analysis other frequencies dominate, so specific formant frequency bands are not easily recognizable. Although the resulting formant map is not much different from the formant map of Peterson, it carries basic information about specific Czech vowels. The results may be used in further research and in education.     

Dynamic characteristics of the human resonance EEG responses to rhythmic photostimulation

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.     

The impact of experimental instruction on changes in EEG power during verbal creative thinking in men and women

Features of EEG pattern during verbal creative thinking depending on experimental instruction were studied in men and women. Spectral power density was analyzed in six frequency bands (4-30 Hz). Performance of a creative task produced an increase in the power of theta (4-6 Hz) and beta2 (20-40 Hz) components and decrease in the power of alpha (8-13 Hz) and betal (13-20 Hz). Changes in the alpha and betal bands were observed, predominantly, in the posterior areas, whereas power of the thetal and beta2 bands increased in the anterior areas. Independently of instruction, women demonstrated greater synchronization in the theta1 band than men, whereas in men the desynchronization in the alpha2 band (10-13 Hz) was more pronounced. When the subjects were instructed to create original sentences, a widespread decrease in the EEG power was observed in the band of 8-30 Hz as compared to instruction "to create sentences". Thus, the instruction-related changes in EEG power were not gender-specific. They may reflect neural activity mediating selective attention.     

Electrographical correlates of adequate and erroneous responses caused by conditioned signals of different functional sign during instrumental conditioning in dogs

Power spectral (in the broad frequency band of 1-225 Hz) of short-term (less than 1 s) EEG reactions were studied in dogs in the course of instrumental food conditioning. These reactions appeared in different cortical areas in response to differentiating signals under conditions of both adequate and erroneous responses. The EEG power of such reactions was several times lower as compared to responses to positive signals, mainly, at the expense of the frequencies in the band of 90-225 Hz (the power of which was higher than that of the traditional band of 1-30 Hz and the gamma band of 30-80 Hz). The frequency composition of EEG reactions accompanying adequate responses was defined, mainly, by discrete subgroups of high-frequency components. During erroneous responses, the discrete structure of the corresponding EEG reactions was broken.     

Gamma band neural synchronization deficits for auditory steady state responses in bipolar disorder patients

Periodic auditory click stimulation has been reported to elicit an auditory steady state response (ASSR). The ASSR has been suggested to reflect the efficiency of γ-amino butyric acid (GABA) inhibitory interneuronal activity. Although a potential role for GABAergic dysfunction has been previously proposed, the role of neural synchronization in the ASSR in people with bipolar disorder (BD) has received little attention. In the current study, we investigated ASSRs to 20 Hz, 30 Hz, 40 Hz and 80 Hz click trains in BD patients. A total of 14 (4 males) BD patients and 25 (10 males) healthy controls participated in this study. ASSRs were obtained using whole-head 306-channel magnetoencephalography to calculate, ASSR power values and phase locking factors (PLF). BD patients exhibited significantly reduced mean ASSR power and PLF values bilaterally at frequencies of 30, 40, and 80 Hz (p<0.05 for these frequencies). At 20 Hz, bipolar patients showed no significant reduction in mean ASSR power and PLF values. There was a significant negative correlation between 80 Hz-ASSR-power values obtained from the right hemisphere and scores on the Hamilton Depression Rating Scale (rho = −0.86, p = 0.0003). The current study showed reduced low and high gamma band ASSR power and PLF bilaterally with no significant beta band ASSR reduction in BD patients. BD patients are characterized by deficits in gamma band oscillations, which may be associated with GABA inhibitory interneuronal activity dysfunction.     

Effect of thyrotropin-releasing hormone (TRH) on EEG topography

EEG topography by a microcomputer system (ATAC-3700 Nihon-Kohden) was performed in the rabbit in order to investigate the mechanism of TRH action on the brain wave. Power spectral analysis was carried out using a fast Fourier transform algorithm. The square root of the power spectra was defined as the equivalent potential over each frequency band by Ueno & Matsuoka's method. Potential fields of EEG frequency band were printed out on the topographic maps. The potentials of the electrocortical delta and theta waves were high, while the potentials of the alpha, beta 1 and beta 2 waves were low. Stimulation of the nucleus ventralis anterior (VA) by 3 Hz and 8 Hz resulted in a decrease in these potentials, especially, those of the alpha, beta 1 and beta 2 waves. The potentials of the alpha and fast waves were increased following unilateral destruction of VA. In the rabbit, in which TRH 0.5 mg/kg had been administered beforehand, there was no decrease in the potential of each wave induced by stimulation of VA with frequencies of 3 Hz and 8 Hz. The findings suggest involvement of the diffuse thalamocortical projection system in the activation of EEG by TRH.     

The mosaic structure of the high-frequency range of neocortical electrical activity in dogs

The study was aimed to reveal the subbands of correlated changes in power spectral density of brain electrical activity (EA), including the low-voltage (up to 10 microV) high-frequency (HF) components (40-200 Hz) in dogs during instrumental conditioning by means of factor analysis. The values of the EA spectral density in interstimulus intervals calculated with a resolution of 1 Hz were used for subsequent factor analysis (the standard principle component technique with varimax rotation). Twenty factors could explain about 80% of total variance. The groups of frequencies which were presented by comparatively narrow peaks (2-3 points) of high loads (more than 0.6) of single factors ("stable" factors) were taken into consideration. In the process of conditioning the factor organization of the EA became substantially complicated, the number of the "stable" factors increased. It was originally shown that the high loads of these factors divided the HF band in comparatively narrow frequency subbands, which appear to reflect the functional mosaics in the neocortex.     

Frequency-dependent response of SI RA-class neurons to vibrotactile stimulation of the receptive field

Three types of experiment were carried out on anesthetized monkeys and cats. In the first, spike discharge activity of rapidly adapting (RA) SI neurons was recorded extracellularly during the application of different frequencies of vibrotactile stimulation to the receptive field (RF). The second used the same stimulus conditions to study the response of RA-I (RA) cutaneous mechanoreceptive afferents. The third used optical intrinsic signal (OIS) imaging and extracellular neurophysiological recording methods together, in the same sessions, to evaluate the relationship between the SI optical and RA neuron spike train responses to low- vs high-frequency stimulation of the same skin site. RA afferent entrainment was high at all frequencies of stimulation. In contrast, SI RA neuron entrainment was much lower on average, and was strongly frequency-dependent, declining in near-linear fashion from 6 to 200 Hz. Even at 200 Hz, however, unambiguous frequencyfollowing responses were present in the spike train activity of some SI RA neurons. These entrainment results support the "periodicity hypothesis" of Mountcastle et al. ( J Neurophysiol 32: 452-484, 1969) that the capacity to discriminate stimulus frequency over the range 5-50 Hz is attributable to the ability of SI RA pyramidal neurons to discharge action potentials in consistent temporal relationship to stimulus motion, and raise the possibility that perceptual frequency discriminative capacity at frequencies between 50 and 200 Hz might be accounted for in the same way. An increase in vibrotactile stimulus frequency within the range 6-200 Hz consistently resulted in an increase in RA afferent mean spike firing rate (M FR). SI RA neuron M FR also increased as frequency increased between 6 and 50 Hz, but declined as stimulus frequency was increased over the range 50-200 Hz. At stimulus frequencies > 100 Hz, and at positions in the RF other than the receptive field center (RF center ), SI RA neuron MFR declined sharply within 0.5-2s of stimulus onset and rebounded transiently upon stimulus termination. In contrast, when the stimulus was applied to the RF center, MFR increased with increasing frequency and tended to remain well maintained throughout the period of high-frequency stimulation. The evidence obtained in "combined" OIS imaging and extracellular microelectrode recording experiments suggests that SI RA neurons with an RF center that corresponds to the stimulated skin site occupy small foci within the much larger SI region activated by same-site cutaneous flutter stimulation, while for the RA neurons located elsewhere in the large SI region activated by a flutter stimulus, the stimulus site and RF center are different.     

Low frequency-dependent mechanism of the M2 receptor function on vagally mediated bronchoconstriction in rabbits in vivo.

The present study was carried out to investigate whether there is the difference between low and high frequencies of vagal stimulation on the functional appearance of M2 receptors in the rabbit. The animals were anesthetized, artificially ventilated and bilaterally vagotomized. Bilateral vagus nerve stimulation (5 to 30 Hz) for 30 sec caused bronchoconstriction (measured as an increase in R(L) and a decrease in Cdyn) in a frequency-dependent manner. The bronchoconstriction evoked by ACh injection (1 and 3 microg/kg) was dose-dependent. Although administration of methoctramine (50 and 300 microg/kg), a selective M2 receptor antagonist, had no significant effect on ACh-induced bronchoconstriction, methoctramine dose-dependently augmented the R(L) and Cdyn responses to vagal stimulation at 5-15 Hz but did not potentiate bronchoconstrictive responses to the stimulation at 30 Hz. Administration of [D-Pro2, D-Try(7,9)]-SP (0.5 mg/kg, a selective tachykinin receptor antagonist) that had no significant effect on the R(L) and Cdyn responses to vagal stimulation (5-15 Hz) attenuated the bronchoconstrictive response to the stimulation at 30 Hz. Conversely, thiorphan (2 mg/kg, a neutral endopeptidase inhibitor) potentiated the bronchoconstriction evoked by vagal stimulation at 30 Hz only. These results suggest that M2 receptors function as the inhibitory receptors in the bronchoconstrictive response to vagal stimulation at the lower frequencies (5-15 Hz), but that the M2 receptor antagonism is diminished when vagal stimulation at a higher frequency (30 Hz) results in the release of SP from the lungs.     

Blood pressure power within frequency range approximately 0.4 Hz in rat conforms to self-similar scaling following spinal cord transection

This study quantified the effect of interrupting the descending input to the sympathetic preganglionic neurons on the dynamic behavior of arterial blood pressure (BP) in the unanesthetized rat. BP was recorded for approximately 4-h intervals in six rats in the neurally intact state and in the same animals after complete spinal cord transection (SCT) between T(4) and T(5). In the intact state, power within the frequency range of 0.35-0.45 Hz was 1.53 +/- 0.38 mmHg(2)/Hz (mean +/- SD by fast Fourier transform). One week after SCT, power within this range decreased significantly (P < 0.05) to 0.43 +/- 0.62 mmHg(2)/Hz. To test for self-similarity before and after SCT, we analyzed data using a wavelet (i.e., functionally, a digital bandpass filter) tuned to be maximally sensitive to fluctuations with periods of approximately 2, 4, 8, 16, 32, or 64 s. In the control state, all fluctuations with periods of >/=4 s conformed to a "self-similar" (i.e., fractal) distribution. In marked contrast, the oscillations with a period of approximately 2 s (i.e., approximately 0.4 Hz) were significantly set apart from those at lower frequencies. One day and seven days after the complete SCT, however, the BP fluctuations at approximately 0.4 Hz now also conformed to the same self-similar behavior characteristic of the lower frequencies. We conclude that 1) an intact sympathetic nervous system endows that portion of the power spectrum centered around approximately 0.4 Hz with properties (e.g., a periodicity) that differ significantly from the self-similar behavior that characterizes the lower frequencies and 2) even within the relatively high frequency range at 0.4 Hz self-similarity is the "default" condition after sympathetic influences have been eliminated.     

Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise

The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians'' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min) of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha) binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians'' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies.     

Developmental changes in neuromuscular transmission in the rat diaphragm.

Neuromuscular transmission was studied in diaphragms from rats of three ages, 4-7 days old, 11-12 days old, and adults with the use of an in vitro phrenic nerve-hemidiaphragm preparation. Each hemidiaphragm was stimulated via either muscle or nerve with 1-s stimulus trains at frequencies from 10 to 100 Hz. The patterns of force development obtained in response to the two routes of stimulation were compared for each group. Diaphragms from adults developed maximum force in response to stimulation of approximately 40 Hz with no significant decrease in force at higher frequencies. Within each stimulus train, once peak force was achieved, it was maintained for the remainder of the stimulus and responses to nerve and muscle stimulation were almost identical. In contrast, diaphragms from 4- to 7-day-old rats developed maximum force at approximately 20 Hz; stimulation at greater than or equal to 60 Hz induced significantly less peak force. This decrease in peak force at higher frequencies was significantly larger for nerve than for muscle stimulation. In addition, during each nerve stimulus train diaphragms from 4- to 7-day-old rats were unable to maintain peak force, which decreased at frequencies greater than 20 Hz. The decrease in force reached approximately 50% of peak at stimulation frequencies greater than or equal to 60 Hz. Diaphragms from 11- to 12-day-old rats showed intermediate responses. Based on the responses to phrenic nerve stimulation, we conclude that the neonatal rat diaphragm shows marked neuromuscular transmission failure that is not seen in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Effects of Alpha (10-Hz) and Beta (22-Hz) “Entrainment” Stimulation on the Alpha and Beta EEG Bands: Individual Differences Are Critical to Prediction of Effects

Two different groups of normal college students were formed: One (the alpha group) received 10-Hz audiovisual (AV) stimulation for 8 minutes, and the other (beta) group received 22-Hz AV stimulation for 8 minutes. EEG power in the alpha (8-13 Hz) and beta (13-30 Hz) bands was FFT-extracted before, during, and for 24 minutes after stimulation. It was found that baseline (prestimulation) alpha and beta power predict the effects of stimulation, leading to individual differences in responsivity. High-baseline alpha participants showed either no entrainment or relatively prolonged entrainment with alpha stimulation. Low-baseline participants showed transient entrainment. Baseline alpha also predicted the direction of change in alpha with beta stimulation. Baseline beta and alpha predicted beta band response to beta stimulation, which was transient enhancement in some participants, inhibition in others. Some participants showed relatively prolonged beta enhancement with beta stimulation.     

Factors affecting central inspiratory modulation of hypoglossal motoneuron activity in newborn pigs

In newborn pigs (4-6 days old), recordings of efferent whole hypoglossal and phrenic nerve discharges were obtained during hyperoxia (or normoxia) and during hypoxia, before and after bilateral vagotomy. With intact vagi, spontaneous hypoglossal inspiratory activity was not observed and was not elicited by either spontaneous changes of electroencephalogram (EEG) or hypoxic stimulation (15% O2 in N2). After bilateral vagotomy, some animals had episodes of spontaneous hypoglossal inspiratory activity; power spectral analysis of EEG demonstrated that this inspiratory activity appeared synchronously with shifts of major peaks in EEG spectra from the delta band (0.5-3.5 Hz) to the theta band (3.5-7.0 Hz). Hypoglossal inspiratory discharges were also elicited by hypoxic stimulation and usually had a decrementing discharge pattern; in some cases, this activity had an augmenting discharge pattern. Our results suggest that hypoglossal motoneurons are poorly modulated by central inspiratory drive, requiring additional facilitatory influences, i.e. corticobulbar, intra-bulbar, chemical drive, before such modulation is observed.     

The significance of the high-frequency components in the cortical potentials of dogs in a study of learning mechanisms

Electrical activity was studied of five different regions of dogs neocortex in inter-stimuli periods in the process of learning of motor habit of pressing the feeder pedal. Epidural electrodes were used. The processing was performed by means of correlation-spectral analysis in a wide band of 1-256 Hz. Values of cross-correlation coefficients, spectra of power, coherence and phase shifts were obtained. In the process of the habit consolidation the high frequencies power increased significantly (within the limits from 60 to 150-170 osc/sec), as well as the part of high coherence (over 0.75), falling on these limits, with low phase shifts. Relatively slow-wave oscillations (1-20 osc/sec) underwent changes of considerably lesser degree. A greater locality of high frequencies (in comparison with the traditional range of 1-20 Hz) was shown. The question of the nature of high frequency EEG components is discussed.     

Children with non-verbal learning disabilities (NLD): coherence values in the resting state may reflect hypofunctional long distance connections in the right hemisphere.

EEG intrahemispheric coherences (HCohs) in the resting state in twenty-four 4 Hz frequency windows between 1 and 51 Hz were studied in 18 children with "non-verbal learning disorder" (NLD) and compared to a group of 18 children with "verbal learning disorder" (VLD). New facts were found in the NLD group. These concern hemispheric balance, expressed as left minus right (L-R) homologous HCohs: 1a). In the high frequencies (25-51 HZ) the number of long-distance HCohs, higher in the right hemisphere (RH), is lower than HCohs, which are higher in the left hemisphere (LH). A reversed interhemispheric asymmetry is seen for short distance HCohs in that band. These asymmetries are not found in the VLD group, and the tendency is even reversed. 1b). In the low frequencies (1-27 Hz) all higher HCohs are more numerous in the RH, irrespective of interelectrode distance (IED). In these bands there are no NLD-VLD group differences; 2). In NLD there is a significant inverse relationship between IED and (L-R)HCoh values (designated as LRDif) in the high frequencies: the larger the IED, the higher the LRDif. In the lower frequencies there is no such tendency. In the VLD group these relationships were absent. These preliminary results suggest long distance gamma band hypoconnectivity in the RH of NLD children, in line with the hypothesis of an RH long distance connectivity problem in NLD. This may explain difficulties with mtermodal perception (gestalt function). Finally in the NLD group some gamma band interhemispheric (ICohs) over F7/F8 and T3/T4 were lower than in VLD children and some gamma band ICohs were higher in NLD compared to VLD over O1/O2. This is possibly connected with the cognitive differences subserved by these areas, i.e., language, respectively visuospatial function.     

The effects of morphine on the relationship between fetal EEG, breathing and blood pressure signals using fast wavelet transform

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.