Spatial synchrony of wader populations in inland lakes of the Iberian Peninsula

Spatial synchronization refers to similarity in temporal variations between spatially separated populations. Three mechanisms have been associated with the spatial synchrony of populations: Moran effect, dispersal and trophic interactions. In this study, we explored the degree of spatial synchrony of three wader species populations (Pied Avocet, Black-winged Stilt and Kentish Plover) using monthly estimates of their abundance in inland lakes of the Iberian Peninsula. The effect of several types of wetland variables (structural, hydroperiod and landscape) on spatial synchronization was explored. Groups of lakes with significant synchronization were identified for all three species. The lakes with wastewater input presented longer hydroperiods than those that did not receive these effluents, and this factor was positively related to the spatial synchrony of the Pied Avocet and Kentish Plover populations. The distance between lakes (used as an indicator of the dispersal effect on synchronization) was significant only in Pied Avocet. No structural or landscape variables were related to spatial synchronization in any species. It was impossible to identify any variable related to the spatial synchronization of Black-winged Stilt abundance as a possible result of the high ecological plasticity of this species. Our data provides the first evidence for mechanisms that act on the spatial synchronizing of wader populations in temporary continental lakes in central Spain, and show that the hydroperiod of lakes acts as an important factor in the spatial synchronization of aquatic species and that its effect is mediated by the reception of urban wastewater.     

Effect of electric stimulation of non-specific and specific thalamic nuclei on the spatial synchronization of cortical potentials in the rabbit

The effect of low-frequency (1-10 Hz) electrical stimulation of nonspecific n. centralis lateralis and n. centrum medianum and specific thalamic (LGB) nuclei on spatial synchronization of biopotentials of neocortical areas and on the process of learning was studied on rabbits. Electrical stimulation of the non-specific nuclei raised the level of correlation of the cortical potentials, while the LGB stimulation, on the contrary, weakened the spatial synchronization between the potentials of the visual and sensorimotor neocortical areas. On the basis of the obtained data a conclusion is made that stimulation of the non-specific thalamus contributes to a more successful formation of defensive conditioned reflex to light unlike LGB stimulation. It is suggested that a certain specificity of the studied subcortical formations in organization of spatial synchronization of the brain biopotentials and in the process of learning is due to morpho-functional peculiarities of these structures.     

Summation of Spatiotemporal Input Patterns in Leaky Integrate-and-Fire Neurons: Application to Neurons in the Cochlear Nucleus Receiving Converging Auditory Nerve Fiber Input

The response of leaky integrate-and-fire neurons is analyzed for periodic inputs whose phases vary with their spatial location. The model gives the relationship between the spatial summation distance and the degree of phase locking of the output spikes (i.e., locking to the periodic stochastic inputs, measured by the synchronization index). The synaptic inputs are modeled as an inhomogeneous Poisson process, and the analysis is carried out in the Gaussian approximation. The model has been applied to globular bushy cells of the cochlear nucleus, which receive converging inputs from auditory nerve fibers that originate at neighboring sites in the cochlea. The model elucidates the roles played by spatial summation and coincidence detection, showing how synchronization decreases with an increase in both frequency and spatial spread of inputs. It also shows under what conditions an enhancement of synchronization of the output relative to the input takes place.     

The role of neuronal synchronization in selective attention

Attention selectively enhances the influence of neuronal responses conveying information about relevant sensory attributes. Accumulating evidence suggests that this selective neuronal modulation relies on rhythmic synchronization at local and long-range spatial scales: attention selectively synchronizes the rhythmic responses of those neurons that are tuned to the spatial and featural attributes of the attended sensory input. The strength of synchronization is thereby functionally related to perceptual accuracy and behavioural efficiency. Complementing this synchronization at a local level, attention has recently been demonstrated to regulate which locally synchronized neuronal groups phase-synchronize their rhythmic activity across long-range connections. These results point to a general computational role for selective synchronization in dynamically controlling which neurons communicate information about sensory inputs effectively.     

Shifts in spatial synchronization of rabbit cortical potentials evoked by applying acetylcholine and amizil to the visual area

Acetylcholine solution application to the visual cortex of walking unrestrained rabbit led approximately in 5 minutes to a certain increase of the spatial synchronization of the cortical potentials at the small conditions, the the cortex, 24 EEG channels being used. Under the same conditions, the application of muscarinic antagonist amizil had an opposite more distinct effect. Endogenous cholinergic input increasing the spatial synchronization is supposed to play an important role in the formation of the spatiotemporal cortical potentials' organization necessary for the occurrence of complex behavioural acts.     

EEG study of the functional organization of the right and left hemisphere during solution of verbal and spatial problems

In adult healthy right-handed subjects, the expression and degree of synchronization of the EEG alpha-range rhythmic components in different areas of the right and left hemispheres, were studied in a state of quiet wakefulness and during solving of verbal and spatial tasks presented in the visual field. The EEG of quiet wakefulness was characterized by different distribution of the alpha-range rhythmic components in the right and left hemispheres; in the right hemisphere low frequencies (7.5-10.5 c/s) were more expressed and more coherent; in the left one--the high frequencies (10.5-13.5 c/s). The solving of tasks was accompanied--along with a decrease of the whole alpha-range power spectra both in the right and the left hemispheres--by a local increase of synchronization of certain components of this range; the increase was specific to the hemisphere and the kind of task. The increase of synchronization of low-frequency components was observed in the right hemisphere during solving of the spatial task and that of the high-frequency components was noticed in the left hemisphere during solving of the verbal task. On the basis of the data on hemispheric specificity of electric activity synchronization of the alpha-rhythm, a suggestion is made about a different character of the functional integration of the structures of the right and left hemispheres in the process of solving of spatial and verbal tasks.     

In search for neurophysiological criteria of altered consciousness

Neurophysiological approaches to brain mechanisms of consciousness are discussed. The concept of spatial synchronization of nervous processes developed by M.N. Livanov is applied to neurophysiological analysis of higher brain functions. However, the spatial synchronization of brain potentials is only a condition for information processing and does not represent it as such. This imposes restrictions on conclusions about the neural mechanisms of consciousness. It is more adequate to use the concept of spatial synchronization in views of consciousness as a psychophysiological level along with sub- and superconsciousness in three-level structure of mind according to P.V. Simonov. Forms of consciousness interaction with other levels concern the problem of altered consciousness and may be reflected in various patterns of spatial organization of brain potentials.     

Gender differences in chronic alcoholism: EEG analysis

Comparative analysis of spatial organization of cortical biopotentials of men (n = 120) and women (n = 75) suffering from alcoholism and persons without addiction to alcohol (control groups) was carried out. Gender differences in the EEG spatial parameters under study (linear spatial synchronization in the brain cortex, non-linear spatial disorder, EEG coherence, and spectral power) were shown to be markedly less pronounced between the control groups (68 women and 85 men) than between the alcohol addicts. The obtained data allow us to explain the known fact of more serious and "malignant" character of alcoholism in women than in men in terms of neurophysiology. In alcoholics, the synchronization of low-frequency oscillations (delta and theta) was higher, whereas the synchronization of the higher-frequency spectrum part (beta1 and beta2) was lower in women than in men. This fact can be a neurophysiological basis of more progredient inhibitory-degenerative processes in women.     

The synchronization of behavior and individual distances in groups of wild boars (Sus scrofa L.)]

Some ways of synchronization are identified in the wild pig behaviour, which are parallel body orientation, group getting together and away, individual approaching and moving away, sound signals. Parallel synchronization is characteristic for various compact groups, males and females exposing some differences in the synchronization duration and distances. The synchronization is mainly a property of individuals united by common motivation and interests. Each family union, each offspring group have their own peculiarities of synchronization depending on their structure. Synchronization duration and distances vary by season, while within- and between-group distances are different in ages and sexes. Two ways of appearance of special distances are recognized. The synchronization works as a trigger system regulation spatial distribution of individuals and various social functions.     

Reduced spike-timing reliability correlates with the emergence of fast ripples in the rat epileptic hippocampus

Ripples are sharp-wave-associated field oscillations (100-300 Hz) recorded in the hippocampus during behavioral immobility and slow-wave sleep. In epileptic rats and humans, a different and faster oscillation (200-600 Hz), termed fast ripples, has been described. However, the basic mechanisms are unknown. Here, we propose that fast ripples emerge from a disorganized ripple pattern caused by unreliable firing in the epileptic hippocampus. Enhanced synaptic activity is responsible for the irregular bursting of CA3 pyramidal cells due to large membrane potential fluctuations. Lower field interactions and a reduced spike-timing reliability concur with decreased spatial synchronization and the emergence of fast ripples. Reducing synaptically driven membrane potential fluctuations improves both spike-timing reliability and spatial synchronization and restores ripples in the epileptic hippocampus. Conversely, a lower spike-timing reliability, with reduced potassium currents, is associated with ripple shuffling in normal hippocampus. Therefore, fast ripples may reflect a pathological desynchronization of the normal ripple pattern.     

Comparative analysis of ethanol effects on the spatial organization of biopotentials under conditions of open and closed eyes during different types of thinking

Effects of low doses of ethanol on indices of spatial organization of cortical potentials (spatial synchronization, coherence, spectral power and information-power index) under the closed- and open-eyes conditions and during performance of divergent and convergent non-verbal and verbal tasks. Ethanol effect was shown to be more expressed under the open eyes-conditions as compared to that with the closed eyes. This finding may be associated with the greater effect of the stream of afferent information in the former case. Changes in topographical characteristics of the spatial synchronization of cortical potentials were more clearly localized and "specific" during divergent thinking as compared to the convergent type. Changes in the spectral power and information-power index testify to greater sensitivity to ethanol of divergent type of thinking as compared to convergent type. Psychological testing of stress resistance and impulsivity also showed a greater effect of ethanol on divergent thinking.     

Adaptive control of an operator’s performance based on biological feedback using the parameters of spatial synchronization of brain cortex areas

The efficiency of an operator’s performance under the determined (D-activity) and stochastic (S-activity) conditions depends on the readiness and synchronization of the frontoparietal and parietooccipital brain cortex areas. The algorithm for the generation of the feedback signal and program of adaptive control based on parameters of these cortical areas’ spatial synchronization were developed. To develop the adaptive control based on this algorithm, two series of experiments on volunteers were performed. The results of the study showed a connection between the initial readiness estimated by Luscher’s test and the efficiency of S- and D-activities modeled by computer games. The objective signs of initial readiness for S- and D-activity were found using parameters of spatial synchronization of the studied cortical areas’ activity in different spectral bands. The possibility of developing adaptive control skills based on the algorithm of the feedback signal generation and maintenance of these skills for one month was also demonstrated. Adaptive control sessions were found to improve characteristics of S- and D-activity, modeled by computer games.     

The effect of acetylcholine on shifts in the spatial synchronization of the cortical potentials in the rabbit evoked by the reversible interruption of the mammillary body connections

To study the role of cholinergic transmitter system in the maintenance of sychronizing limbic influences, the dynamics of the spatial distribution of the changes of cross-correlation coefficients of rabbits EEG led by 24 electrodes, was estimated at application of acetylcholine solution to the visual cortical area in combination with anode polarization of mammillary bodies. Acetylcholine, which separate effect was connected with a restricted increase of the spatial synchronization of potentials, completely eliminated the effects of isolated polarization expressed in a significant decrease of a half of calculated correlation coefficients between EEGs of the visual and motor cortical areas. Nonspecific cholinergic synchronizing system is supposed to exist which is active under the conditions of the mammillo-thalamo-cortical connections being intact.     

Spatial synchronization of rabbit brain biopotentials upon repeated electrical stimulation of the cortex]

A study was made on 23 rabbits of the degree of spatial synchronization in response to repeated electrical stimulations of one or simultaneously two cortical areas: the sensorimotor or visual, or simultaneously the sensorimotor and visual, or sensorimotor and precentral respectively. Enhancement of the synchronization induced by the stimulation, globally spread over the entire cortex and was followed by its decrease. However, in the two directly stimulated areas of the cortex, the similarity of bioelectrical oscillations persisted for a long time, which testifies to the establishment of selective relations between them.     

Excitability of the sensomotor cortex and red nucleus of rabbits at different levels of spatial synchronization of cortical potentials

To determine the excitability of the rabbit sensomotor cortex and red nucleus the animal's motor response to electrical stimulation of these structures at threshold strength was investigated. In computerized experiments the excitability of these structures was compared in situations characterized by different degrees of correlation of cortical potentials. An increase in the level of spatial synchronization of cortical potentials was shown to be accompanied by an increase in the excitability of the sensomotor cortex and red nucleus. This increase in excitability is evidently a neurophysiological mechanism of the increase in probability of appearance of an effector response to sensory stimulation when the level of spatial synchronization of cortical potentials is raised.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 19–24, January–February, 1977.     

祁连山红腹牧草蝗雌雄虫空间格局及关联性

应用地统计学的方法,研究了祁连山北坡石羊河上游,6—10月之间红腹牧草蝗Omocestus haemorrhoidalis(Charpentie)雌雄虫的空间分布格局、动态变化及空间相关性。结果表明:红腹牧草蝗雌雄虫的半变异函数为球状模型与高斯模型,二者空间分布类型相同,均呈聚集分布;随时间的变化均呈现"扩散-聚集-扩散-聚集"的动态特征,7—8月之间雌虫的变化强度明显强于雄虫;二者的模糊贴近度指数在0.53～0.71之间,且指数随红腹牧草蝗的生长呈逐渐增加到减少的变化特征,表明雌雄虫在数量与空间上有较强的跟随关系,且跟随关系随红腹牧草蝗的生长发生明显的阶段性变化。     

Features of spatial organization of EEG and psychophysiological characteristics of the person with the divergent and convergent types of thinking

The psychophysiological indicators of spatial synchronization of biopotential at different types of mental processes in humans: non verbal-divergent, nonverbal-convergent, verbal-divergent and verbal-convergent were analyzed. The unequal relationship between the productivity of the implementation of tests on these types of thinking was revealed. The closest significant correlation exists between the productivity of the verbal-divergent and verbal-convergent thinking, and the lowest--between the productivity of nonverbally-divergent and nonverbally-convergent thinking. The differences in the topographical maps of the spatial synchronization of biopotential at different types of thinking was marked. They are most pronounced in the implementation of two non-verbal tasks, minimal--in two verbal tasks. Differences between different types of thinking are also manifested in the degree of coherence gain biopotential of the performance tests in comparison with the background (open eyes). Some physiological properties of the person that contribute to the divergent (creative) tests have a negative impact on the implementation of converged (tedious) tests. The findings are discussed in terms of differences in the level of general activation and participation of different ways of processing information (simultaneous and successiveness).     

Assessment of spatial organization in the atria during paroxysmal atrial fibrillation and adrenergic stimulation.

Non-linear parameters were computed to assess the extent of spatial organization in the atria in terms of coupling/synchronization between electrograms recorded in different atrial sites. Recordings of 9 patients suffering from paroxysmal atrial fibrillation were tested during four clinical experimental conditions: sinus rhythm and atrial fibrillation, both before and after isoproterenol infusion, a drug mimicking adrenergic activation. Two non-linear metrics were investigated: an index of non-linear association (NLA) and a synchronization (S) index based on the cross-conditional entropy. Results evidence the presence of reduced coupling after drug infusion in both sinus rhythm and atrial fibrillation. Moreover, passing from the NLA to the S index, the capability of the parameter to capture the subtle changes due to isoproterenol administration increased.     

Adjusting neurophysiological computations in the adult olfactory bulb

The olfactory bulb receives signals from olfactory sensory neurons and conveys them to higher centers. The mapping of the sensory inputs generates a reproducible spatial pattern in the glomerular layer of the olfactory bulb for each odorant. Then, this restricted activation is transformed into highly distributed patterns by lateral interactions between relay neurons and local interneurons. Thus, odor information processing requires the spatial patterning of both sensory inputs and synaptic interactions. In other words, odor representation is highly dynamic and temporally orchestrated. Here, we describe how the local inhibitory network shapes the global oscillations and the precise synchronization of relay neurons. We discuss how local inhibitory interneurons transpose the spatial dimension into temporal patterning. Remarkably, this transposition is not fixed but highly flexible to continuously optimize olfactory information processing.     

The functional significance of synchronization of cortical potentials in humans

The dependence between the level and the topography of spatial synchronization of cortical potentials and the manifestation of motor reactions to light stimuli was studied in humans. To evaluate the spatial synchronization of potentials the correlation coefficients () were calculated between three points of the motor area and each of three occipital points of the cortex. The calculation was made using a computer with direct input of the potentials. At a definite level of the machine switched on a light stimulus and a mechanism recording the motor reaction. The experiments have shown that the higher the number of pair derivations giving a high value of , the more often movements are caused. Moreover it became apparent that the pattern of correlation ratios between the derivations depends on the motor reactions. In the case of movements a significant constancy of the ratios between individual derivations was found. It is shown that the spatial synchronization of potentials in the human cerebral cortex has a functional significance. However, this synchronization does not reflect the realization of movements but only the conditions required for them.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 166–172, March–April, 1970.