Showing papers in "Fiziologiia cheloveka in 2003"

Study of the brain organization of creative thinking

Abstract: This article is a continuation of a series of works on the brain organization of creative thinking. It was shown in earlier studies that, when solving creative tasks, subjects choose between two strategies (successive and insight), and the results of the study of the brain mechanisms of the successive strategy were described [1–3]. The results of positron-emission tomography (PET) study of the second (insight) strategy of solving creative tasks are presented in this communication.

EEG local and spatial synchronization during a test on the in site strategy of solving creative verbal tasks

Abstract: In earlier studies of brain mechanisms of creative activity that were performed at the Institute of the Human Brain, Russian Academy of Sciences, it was found that, during composition of a story including words from different semantic fields, subjects used either a strategy of “uniform” work on the text (a successive, noninsight strategy) or a strategy of deferred, “impulsive” generation of a story immediately before or even during a report (an insight strategy) [1]. At the previous stage, we examined subjects using only the noninsight strategy [2, 3]. In this communication, we present the results of EEG analysis of subjects during their performance of a task requiring the insight strategy. The subjects were presented with two kinds of tasks: (1) in the test task, task D (a variation of Mednick’s remote association test), a subject had to link a “difficult” sequence of 12 words from different semantic fields with associated words (nouns); (2) in the control task, task E (a variation of the generalization test applied in clinical psychology), a subject had to choose five concrete examples (objects or phenomena) belonging to a given word category in response to words of these categories presented in random order (“easy” sequences). Two groups of subjects participated in the study. The first group (15 subjects) comprised first-year students of the Faculty of Acting of the State Academy of Dramatic Art (9 men and 6 women). The second group (15 subjects) comprised students of different St. Petersburg higher educational institutions (7 men and 8 women). The subjects performed each task in silence within a period of 10 s after its administration. The EEG was recorded over the course of this period. They then gave an oral report after a signal. The monopolar EEG was recorded in 19 standard derivations (10/20 system) in reference to linked earlobe electrodes in the frequency band 1.5–30 Hz with a sampling rate of 125 Hz. During the task performance, ten 1-s EEG segments were recorded. The records were analyzed visually, and EEG segments with visible artifacts were excluded from the subsequent analysis. The EEG quantitative characteristics were calculated by means of the WinEEG software package, developed by V.A. Ponomarev. In this communication, we deal with estimations of the EEG absolute spectral power and coherence function (characteristics of the local and spatial EEG synchronization, respectively), summed in the following frequency bands: ∆ (1.5–3.5 Hz), θ (4–7 Hz), α 1 (7.5–9.5 Hz), α 2 (10–12.5 Hz), β 1 (13–18 Hz), and β 2 (18.5–30 Hz). Arrays of the estimations, averaged for each subject during performance of each task, were normalized using the transforms Y =

Characteristic fetures of EEG spectral characteritics in persons with deviant sexual behavior

Abstract: The study was performed with participation of 59 right-handed men. The normal group consisted of 19 subjects, and 40 patients with organic brain lesions who had commited sexual offenses were divided into two groups: 19 patients with a diagnosis of paraphilia (pathology of sexual drive) made up the main test group, and 21 patients without such a diagnosis formed the control group. A monopolar EEG was recorded in 16 standard leads in the states of rest (eyes closed) and general activation (eyes open) and during presentation of cognitive tests. The following EEG features manifest in all the frequency ranges and functional states were revealed in the group of patients with paraphilias as compared to the control groups: a substantially increased level of interhemispheric coherence (ICoh) and increased spectral density in the posterotemporal area (T5, T6), a significantly decreased ICoh level between the F3/4 and C3/4 leads in the frontocentral area, and lower spectral densities in the leads Fp2, C4, and P4. Analysis of reactions to loads presented showed that the general arousal in the group of patients with paraphilias was characterized by significantly greater shifts of EEG parameters associated with the desynchronization reaction (as compared to the control groups) and statistically significant disorders of interhemispheric interaction and EEG reactivity in the right hemisphere in the β range during performance of a visuospatial (“right-hemispheric”) task. The results suggest the formation of a stationary activation focus in the right hemisphere with signs of involvement of the limbic structures in patients with paraphilias.

Thermoregulation and blood circulation in adults during short term exposure to extreme temperatures

Abstract: Two groups of male and female subjects aged 36–50 years were examined prior to and after short-term exposure to extreme temperatures. One group was exposed to heating in a sauna, and the other was exposed to cooling in ice-cold water. In both cases, the changes in some indices of thermoregulation and blood circulation approximated critical values. It is therefore concluded that, in adults, such procedures are stressful and dangerous for health.

Automatism or rhythmogenesis in the respiratory center

Abstract: The results of experimental and simulation studies of the mechanisms of rhythmogenesis in the respiratory center accumulated in recent decades are analyzed and summarized. The best grounded and most consistent hypotheses on the structures and functions of medullary rhythm-generating formations are compared. Undeniable advantages and some drawbacks of each hypothesis are discussed. Promising ways for solving the problem of respiratory center automatism, which is among the most important issues in general biology and neurophysiology and a pivotal problem of respiration physiology, are outlined.

Psychophysiological features of somatosensory disorders in victims of the Chernobyl accident

Abstract: Participants of the Chernobyl clean-up ( n = 145) teams exposed to radiation doses from 0.05 to 3.5 Gy who had for the first time complained of pathologic somatosensory sensations (ostealgic syndrome), 20 healthy subjects, and 50 veterans of the war in Afghanistan with posttraumatic stress disorder (PTSD) were examined by a neuropsychiatrist and presented with the MMPI test. Somatosensory evoked potentials (SSEPs) were recorded. Paresthesia and cenesthopathy were characteristic of the participants of the Chernobyl clean-up. Sensation disorders of the cerebral type, kinesthetic illusions, cenesthopathic hypochondriac disorders, and par- oxysmal psychosensory states predominated in this group of subjects. They differed significantly from the vet- erans with PTSD in markedly increased scores on MMPI scales (hypochondriasis, schizophrenia, pure hypo- chondriasis, pure schizophrenia, emotional exclusion, and perception oddity), which closely correlated with clinical somatosensory symptoms. In clean-up workers, somatosensory disorders were significantly associated with hypochondriac and schizophrenic-like symptoms. The latencies (LPs) of main SSEP components— N 20 , P 25 , N 140 , P 300 , and N 400 —were increased and their amplitudes decreased in subjects exposed to radiation. Their SSEPs had significant topographical deviations in the left temporoparietal area: the contralateral LPs were increased, whereas the contralateral amplitudes of the thalamocortical N 20 component and the cortical P 25 com- ponent were decreased as compared to normal values. Somatosensory disorders and hypochondriac and schizo- phrenic symptoms were significantly correlated with changes in the SSEPs. The decrease in the N 20 amplitude and increase in the P 25 latency in the left temporoparietal area were dose-dependent. The results suggest cere- bral rather than peripheral origin of ostealgic syndrome and other somatosensory disorders in the participants of the Chernobyl clean-up. These disorders are associated with radiation-induced dysfunction of the corticolim- bic structures of the left—dominant—hemisphere. It is suggested that somatosensory disorders in patients exposed to low doses of radiation can be considered as manifestations of chronic fatigue syndrome /fibromyalgia, whereas schizoform organic brain lesions manifest themselves after exposure to a radiation dose of 0.3-0.5 Gy.

The role of the genotype in the development of neurophysiological mechanisms involved in the space integration of the neocortex bioelectric activity

Abstract: The contribution of genetic factors into the formation of the neurophysiological mechanisms determining the systemic organization of cortical activity has been estimated in 12 pairs of monozygotic (MZ) and 5 pairs of dizygotic (DZ) twins (18–25 years of age). The similarity of individual patterns of the spatial interaction of cortical bioelectric activity measured for different combinations of EEG statistical relationships from 16 monopolar leads has been estimated in each pair of twins and in each of the 544 pairs of unrelated subjects in both groups. The results of the study suggest a high population invariance and small genetic and phenotypic variations of the morphofunctional systems constituting the main neurophysiological mechanisms of general cerebral integration. Brainstem and subcortical regulatory structures play the leading role in the integration of different brain regions into an organized system. Apparently, the formation of these structures during ontogeny follows the same general pattern in all individuals, because deviation from it is likely to affect the fundamental monomorphic characters of the species. The formation of neocortical interregional connections may be expected to exhibit greater individual variation, with the roles of hereditary and environmental factors in the formation of long and relatively short intercortical interactions being different. Apparently, the individual variation of the long intra- and interhemispheric fiber pathways forming the specific morphological framework of the neocortex is largely determined by the genotype. However, the intercentral interactions mediated by short corticocortical connections that are formed in the course of the vital activity of an individual are likely to be mainly determined by the external and internal environments.

Lateralization of motor functions in early human ontogenesis

Abstract: This study was aimed at testing the hypothesis about the development of lateralization of frontal motor control (FMC) as a source of preference of the right hand human in early ontogeny. The sample consisted of 108 children aged from 8 months (the initial stage of maturation of inhibitory control in reaching) to 11 months (the definitive stage). The main results showed the following: (1) at the population level, the preference of the right hand in the performance of tests that require a definite level of development of FMC appears only at the age of 11 months, i.e., synchronously with development of frontal inhibitory control of reaching; (2) the preference of the right hand is substantially stronger in 11-month-old children with a higher level of development of inhibitory motor control as compared to other children of the same age; (3) the preference of the right hand is most evident for those movements that require inhibitory control (i.e., controlled reaching). On the whole, the data obtained show that the appearance of a preference for the right hand in the second half-year of the life of an infant is caused by the development of cortical inhibitory control over motor acts (FMC), associated with the maturation of the frontal neocortex.

Reflection of the intelligence structure in the spatiotemporal features of baseline EEG

Abstract: The EEG correlates of the verbal, numerical, and figural IQ components according to the power and coherence characteristics of the baseline EEG in six frequency bands were studied taking into account personality traits of subjects (extroversion, neuroticism, psychoticism, and anxiety). Analysis of variance and correlation showed that a decreased power of the low-frequency θ1, 2and α1 rhythms and increased EEG power in the β2 band with the right-hemispheric dominance were characteristic of persons with higher intelligence. These EEG characteristics were associated with increased interhemispheric interaction according to the coherence indices and increased coherence within the right hemisphere. Each of the intelligence components (verbal, numerical, and figural) was characterized by a specific baseline frequency–spatial EEG pattern distinguished by specific interactions, predominantly, between the frontal and caudal cortical regions in the θ and/or β2 frequency bands.

[Age-related features of the voluntary control of the upright posture].

Abstract: The capability for the unconscious control of the upright posture in elderly people is impaired, which increases the risk of falls and traumata. The impairment of the unconscious control of posture is partially compensated by the fixation of voluntary attention on the maintenance of an appropriate posture. Elderly people fall predominantly during the performance of movements that demand additional voluntary postural control, for example, unstable support conditions. Thus, voluntary postural control assumes importance in elderly persons. Since it is unclear whether this function changes with age, the aim of this work was to study age-related features of the learning voluntary postural control using visual feedback by center-of-pressure position. The results of the study showed that voluntary postural control is a complex multicomponent process that includes, at least, the following functions: selection of a strategy of postural control, its actualization, and precision of its regulation. With aging, strategy selection in healthy people impairs, but both elderly and middle-aged people can learn this function as successfully as the young. At the same time, despite the absence of an initial deficit in the accuracy of postural setting in elderly people, training of this function becomes substantially more difficult with age.

Subjective and Neurological Manifestations of Hyperventilation States of Different Intensities

Abstract: Detailed analysis of the subjective sensations of 135 healthy subjects during 20- to -30 min voluntary hyperventilation was performed. The hyperventilation levels (V EI = 20 l/min, V EII = 30 l/min, V EIII = 40 l/min) were chosen so that manifestations of paroxysms of hyperventilation syndrome (HVS) of different severity were simulated. Regular features in the time course of development of HVS symptoms were revealed: (1) specific peripheral subjective sensations and symptoms changed consistently, being peculiar sensory equivalents (correlates) of hyperventilation-related changes in gaseous metabolism and acid-base balance; (2) sensations and symptoms of central origin developed in waves, with considerable individual variations in manifestation and emotional hue and were closely correlated with changes in systemic hemodynamics and brain circulation disorders.

Perception of a spectrally deprived speech signal

Abstract: It was found that, at a test bandwidth range of 50 Hz, 100% speech intelligibility is retained in naive subjects when, on average, 950 Hz is removed from each subsequent 1000-Hz bandwidth. Thus, speech is 95% redundant with respect to the spectral content. The parameters of the comb filter were chosen from measurements of speech intelligibility in experienced subjects, at which no one subject with normal hearing taking part in the experiment for the first time exhibited 100% intelligibility. Two methods of learning to perceive spectrally deprived speech signals are compared: (1) aurally only and (2) with visual enhancement. In the latter case, speech intelligibility is significantly higher. The possibility of using a spectrally deprived speech signal to develop and assess the efficiency of auditory rehabilitation of implanted patients is discussed.

Human assessment of signals modeling different directions of the motion of sound images

Abstract: The characteristics of a subjective sound field formed under conditions of dichotic stimulation were studied in healthy subjects (six females and seven males) with normal auditory sensitivity upon movement of a sound image (SI) in different directions. The character and the trajectory values of the emerging subjective sound image (SSI) were determined depending on the direction of its motion and the initial interaural delay (700, 400, and 200 μs). Certain differences in the assessment of the parameters of moving sound images between the groups of male and female subjects were revealed. In female subjects, the averaged trajectory values in the right and left hemispheres were the same when the SSI moved in both directions and shortened uniformly with a decrease in the initial interaural delay. With a 700-μs delay, the trajectory values of the male subjects for all directions of motion of the SSI were the same as those of female subjects. With initial 400- and 200-μs delays, the trajectory values were significantly greater in the group of male subjects if a SI moved from the right or left ear to the median line of the head. With the method used, no interhemispheric asymmetry was revealed in the process of lateralization of moving sound images, which, under certain conditions, may be of importance for increasing the accuracy of localization of sound sources in the environment.

Erythrocyte aggregation in athletes

Abstract: Erythrocyte aggregation (examined microscopically in diluted blood), lipid and protein plasma profiles, and fibrinolytic activity were studied in endurance athletes. Division of the athletes into two subgroups by cluster analysis showed that a higher level of fitness was associated with a lower plasminogen activity; enhanced fibrinolysis; increased blood fluidity; lower fibrinogen, cholesterol, and triglyceride levels; a relatively low erythrocyte aggregation index; and high suspension stability of the blood. Fibrinogen was the key plasma factor determining erythrocyte aggregation. Its level was closely correlated with plasminogen activity. Discriminant analysis showed that most differences between groups of athletes were connected with plasminogen activity, the von Willebrand factor, and fibrinolytic activity.

The Role of the Initial State in the Response of the Hemostasis System to Double Exercise

Abstract: Changes in the hemostasis system were studied in males with a high working capacity when they performed the same dosed double stress exercise test with moderate ( N 1 = 1.4 W/kg, t 1 = 6.93 min) and high ( N 2 = 2.96 W/kg, t 2 = 3.15 min) intensity with a 1-h interval between. The direction and the magnitude of changes in the main variables of blood coagulation, anticoagulants, and blood and plasma fibrinolytic activity under the influence of exercise were shown to correlate with the initial state of the system. At high values of the variables before the beginning of muscular activity, work results in their decrease, and at low values, in their increase. Previous work increases the dependence of changes in blood coagulation on its initial value upon repeat exercise, without influencing the relationship between alterations in the fibrinolytic activity of whole blood and its value before exercise. Double loading reveals closer relations between the initial values of blood coagulation, anticoagulants, and fibrinolysis and their changes due to work. It was concluded that, on the basis of the correlations presented, it is possible to predict with high probability the direction and the magnitude of hemocoagulant and fibrinolytic response to physical activity in the group of subjects studied.

[Studies of physiological effects of the breathing of heated oxygen-helium mixtures].

Abstract: The use for breathing of oxygen–helium mixtures (OHMs) heated substantially above the range of temperatures thermoneutral for humans is considered. The following results were obtained in experiments with volunteer subjects: (1) breathing of heated OHMs during recovery after exercise resulted in a decrease in the maximum concentration of lactic acid in the blood; (2) during and after breathing of heated OHMs, there was an increase in the lung diffusion capacity.

Functional State of 11- to 12-Year-Old Schoolchildren under Conditions of Intense Academic Load Assessed by Heart Rate Variability

Abstract: The functional state of sixth-grade children was estimated on the basis of heart rhythm variability data. It was found that the heart rate variability was closely correlated with learning progress during both intensive and nonintensive methods of education. The highest adaptation tension was observed in children with good learning progress during intensive methods of education.

Comparison of the antidiuretic response of kidneys to different modes of vasopressin administration

Abstract: The effect of vasopressin given simultaneously with a water load was studied in healthy human volunteers. During maximal water diuresis induced by oral water load of 20 ml water per kilogram body weight, the excreted water fraction was 12.4%, whereas the excretion of osmotically free water was 10.0 ± 1.8 ml/min per 1.73 m2 of body surface area. These data suggest that the secretion of arginine vasopressin by the neurohypophysis was almost completely blocked. A water load simultaneously with 8 μg sublingual or 0.2 mg oral desmopressin caused a strong and long-lasting antidiuretic response accompanied by a drastic increase in the reabsorption of osmotically free water in the kidneys. It was shown that the magnitude and the time course of the antidiuretic response to therapeutic doses of desmopressin depended on the mode of its administration.

Rearrangement of total electrical activity of the cerebral cortex and subcortical structures in experimental hypoxia

Abstract: Rearrangements of the parameters of the electric activity of the cortical and subcortical regions were studied at different stages of experimental hypoxia (exposure to oxygen–nitrogen mixtures with an oxygen content of 7.5–8.0%) in chronic experiments of rabbits with the use of electrodes implanted into the brain. Acute hypoxia was shown to cause characteristic changes in electrical activity in the cortex, reticular formation, caudate nuclei, and hippocampus. The sequence of these changes may be divided into the following stages: (1) a short-term activation of all cerebral structures during the first 15–30 s and a shift of the frequency spectrum towards higher frequencies (β and α waves), (2) a decrease in β and α waves and an increase in θ activity during the next 2–4 min, and (3) a gradual shift towards slow waves (the Δ rhythm) and paroxysmal episodes in some animals. These shifts first appear in the frontal cortical regions and the reticular formation and then in the caudate nuclei and hippocampus. The degree of the changes in electric activity is correlated with the decrease in oxygen tension in the arterial blood.

[Menstrual rhythm, menstrual interval and duration of menstruation in left-handed and right-handed women].

Abstract: Functional brain asymmetry (FBA) is gaining recognition as an important biological phenomenon in modern medicine [1, 2]. As the number of studies concerning this phenomenon grows, it is becoming clear that FBA may be of clinical and fundamental significance. For instance, several correlations have been detected between handedness, which usually serves as an index of hemispheric asymmetry, and autoimmune [3], neuropsychiatric [4], and neoplastic [5] diseases. Handedness-related differences have also been detected in autonomic and neuroendocrine regulation [6], adaptive capacities [7], and so on. The reproductive system occupies an important place in these studies. Within the framework of the concept of cerebral lateralization, geschwind and galaburda were [8] the first to suggest that sexual and reproductive functions vary among women depending on their handedness. This hypothesis was indirectly confirmed by the data of Tan [9], who demonstrated that serum estradiol levels are negatively correlated with the degree of right-hand preference in women and that serum testosterone concentrations are significantly higher in left-handers than in right-handers whether men or women.

Pulse rate criteria for determining the energy cost of exercise

Abstract: From the pulse rate curve taken during exercise and recovery from highly qualified sportsmen performing a bicycle exercise test at a maximum workload, the work pulse sum, pulse debt, and pulse cost were calculated. Plots of these indices versus the time to exhaustion and versus the relative exercise workload were identical to the respective plots of oxygen consumption during exercise, oxygen debt, and oxygen requirement. The exercise pulse cost can serve as a criterion for quantifying physical workloads.

[Hemispheric asymmetry of evoked potentials during performance of visuo-spatial tasks].

Abstract: We studied the time and amplitude parameters of visual evoked potential components during performance of a visuospatial task under conditions of involuntary and voluntary attention. The right hemisphere dominated to a great extent with respect to the latencies of the components studied. Transient stagewise dominance of each hemisphere with respect to the level of cortical activity was also observed.

[Analysis and evaluation of the functional state of cardiovascular system in cosmonauts during long-term space flights].

Abstract: Forty-four cosmonauts participating in 28 main long-term (73–438 days) missions on the Mirorbital station performed functional tests with graded physical exercise using a bicycle ergometer. There were two types of this functional load. The cosmonauts that participated in the first eight main missions performed a two-step exercise with a total load power of 1150 W. In the remaining cosmonauts, the exercise was three-step, with a total power of 1350 W. The results obtained during the flight were compared with the results of the same tests performed before the flight, which served as control values for each cosmonaut. To estimate the load tolerance, the heart rate (HR), systolic blood pressure, stroke volume (SV), cardiac output (CO), and cardiac index were analyzed. The data were grouped according to the load, taking into account the type of blood circulation for each group before and during the flight. The ratio between different types of blood circulation was found to change during the flight. The responses to both types of exercises before the flight were less favorable in the cases of the hyperkinetic type of circulation. In these cases, the dominance of the chronotropic function of the heart determined the increase in CO. In the cases of the hypo- and eukinetic types of circulation, the response to the exercise was close to normotonic. In microgravity, irrespective of the circulation type and the exercise, the mechanism of the CO formation changed: the effect of HR was dominant, and there was no increase in SV. Insufficient venous return to the chambers of the heart is the main cause of the decreased response of SV to exercises during spaceflight.

Spectral analysis of long electroencephalographic records

Abstract: Spectral analysis of a 10-min electroencephalogram (EEG) record has made it possible to describe the behavior of EEG rhythms as a dynamic spectrum and find a distinct periodic pattern in this behavior. The data on the dynamic spectra of long EEGs offer a new insight into the estimation of the stability of EEG electrical processes in healthy subjects, inter- and intrahemispheric relationships between the electrical activities of different cortical regions, and estimation of phase relations, which were previously performed on the basis of comparison between single EEG spectral patterns.