The EEG spatial pattern and psychophysiological characteristics of divergent and convergent thinking in humans

The psychophysiological parameters of the spatial synchronization of bioelectric potentials during the nonverbal divergent, nonverbal convergent, verbal divergent and verbal convergent thinking have been analyzed. The relationships between the performances of tests for these thinking styles were different. The strongest significant correlation has been found between the productivities of the verbal divergent and verbal convergent thinking styles; the weakest correlation, between those of the nonverbal divergent and nonverbal convergent thinking styles. The thinking styles differ from one another in the topography of spatial synchronization of bioelectric potentials. They are the most pronounced during the two nonverbal tasks and the least pronounced during the two verbal tasks. The thinking styles also differ from one another in the degree of the enhancement of the coherence between bioelectric potentials during tasks compared to the baseline (with the eyes open). Some human psychophysiological characteristics facilitating the performance of divergent (creative) tasks have a negative effect on the performance of convergent (noncreative) tasks. The data are discussed in terms of the differences in the level of general activation and involvement of different types of information processing (simultaneous and successive).     

Indices of Coherence of EEG Rhythms in the Course of Cognitive Activity as Markers of Creative Thinking: Gender Specificity

According to the results of psychological testing, persons aged 18 to 21 years were divided into four groups, women and men with low and high productivity of divergent (creative, nonroutine) thinking (n = = 18 to 23). Results of EEG recording (19 leads) were used for calculation of the coherence coefficients for oscillations of the delta, theta, alpha1, alpha2, alpha3, beta, and gamma frequencies in lead pairs and estimation of integral indices of coherence within the anterior and posterior cortical regions and between these zones (interaction coefficients, IC1-IC3, respectively). EEG was recorded in the resting state and in the course of resolving convergent- and divergent-type cognitive test tasks. It was found that, during the performance of tests of both types, men with a higher productivity of divergent thinking demonstrated significantly higher values of IC1 (that characterizes the coherence in associative linkages within the anterior cortex) for oscillations of all EEG frequency ranges compared with the respective estimates for “low-creative” men. Similar increments were typical of the IC2 values for low- and midfrequency EEG rhythms (delta, theta, and alpha). At the same time, values of the “interregional” IC3 for theta, beta, and gamma activity in “high-creativity” men were significantly lower. In women of both groups (low and high creativity), such specificity of the IC1-IC3 patterns was practically not observed, i.e., the respective aspect demonstrated clear gender specificity. The sex of the subjects and type of the performed cognitive tests could not be considered factors significantly affecting the calculated absolute IC values. The observed specificities of integral coherence indices are probably associated with different strategies of the performance of cognitive tasks in men and women. Our findings allow us to believe that the above interrelations between integrated coherence indices can be used as EEG markers of high productivity of divergent thinking in men. The more flexible strategies of thinking in women are probably related to more variable neurophysiological cortical mechanisms (compared with those in men), and this type of organization is not clearly reflected in the pattern of intracortical interactions estimated by coherence indices.     

Comparative analysis of spatial EEG organization on models of non-verbal divergent and convergent thinking

Features of neurophysiological organization of two main thinking types playing different roles in creative processes, i.e., divergent and convergent were studied with participation of 30 right-handed male subjects at the age from 30 to 50 years. Two tests were presented: (1) creation of many visual images on the basis of two simple geometrical figures (the model of divergent thinking) and (2) classification of a figure element with one of the offered standard samples (convergent thinking). The number of created images or correctly classified elements for five minutes served a criterion of performance productivity. It was found that performance of the divergent test with high productivity (as compared to low productivity) was characterized by a greater increase in non-linear interactions between the cortical potentials, especially in the axis right frontal--left occipital areas. At the same time, under conditions of high productivity, the number of active narrow-frequency spectral-coherent EEG bands increased. The data confirm the notion of neurophysiological organization of creative processes, according to which creative processes require the intensification of retrieval operations (both conscious and unconscious), based on extensive interhemispheric interaction and involvement of a system of EEG coherent structures oscillating with different frequencies.     

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.     

Total bioelectrical activity of the sensorimotor and visual cortices in rabbits during early neurological disorders from gamma irradiation at high doses

The overall bioelectrical activity of the sensorimotor and visual brain cortex of rabbits was estimated during early neurological impairment caused by 120 Gy gamma-irradiation. The characteristic changes were revealed in the amplitude, form, energy spectrum and spatial biopotential synchronization. The changes in the bioelectrical activity of the brain were associated with the clinically displayed stages of the neurological process development.     

Testing the correlation between beta diversity and differences in productivity among global ecoregions,biomes, and biogeographical realms

Considerable amount of research on the relationships between species diversity and productivity at different spatial, ecological, and taxonomic scales has been conducted. However, the overall trend of the correlation at the global scale still remains sketchy and the causal relationship between species diversity and productivity needs further exploration. This is especially true with beta diversity since most studies carried out use alpha diversity as the general term for species diversity. In this study we use the MODIS NDVI as the surrogate of productivity, and the WWF ecoregion systems and its species distribution information to test correlations between beta diversity and differences in productivity at various taxonomic ranks on a global scale. Matrix correlation is performed between species composition measured as beta diversities using Sørensen similarity index and MODIS NDVI/productivity measured as Bhattacharyya distances through Mantel permutation tests. The correlation coefficients and Mantel test significance levels are reported at the global ecoregion, biogeographical realm, and biome levels respectively. Significant correlations are found at all three taxonomic ranks. Results from realm and biome tests suggest that the highest correlations are reached at the temperate regions when species rank is used. Our findings suggest that species' natural spatial boundaries, such as the biogeographical realms or biogeographic kinship play a critical role in shaping the correlation patterns between beta diversity and productivity differences at the global scale.     

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.     

Space-time organization of the electrical activity of the human brain in a state of calm wakefulness and during the solution of intellectual tasks

In a series of experiments it has been shown that during solution of mental tasks of various complexity, a marked desynchronization is observed of the cortical rhythmic activity characteristic of the state of calm wakefulness. In the range of main wakefulness frequencies (alpha and beta), a significant lowering is observed of the level of spatial biopotential synchronizations. Its increase in these conditions is connected with the range of slow EEG rhythms; there exist different opinions about their functional significance in wakefulness.     

Bird diversity patterns in Neotropical temperate farmlands: The role of environmental factors and trophic groups in the spring and autumn

Productivity, habitat heterogeneity and environmental similarity are of the most widely accepted hypotheses to explain spatial patterns of species richness and species composition similarity. Environmental factors may exhibit seasonal changes affecting species distributions. We explored possible changes in spatial patterns of bird species richness and species composition similarity. Feeding habits are likely to have a major influence in bird–environment associations and, given that food availability shows seasonal changes in temperate climates, we expect those associations to differ by trophic group (insectivores or granivores). We surveyed birds and estimated environmental variables along line‐transects covering an E‐W gradient of annual precipitation in the Pampas of Argentina during the autumn and the spring. We examined responses of bird species richness to spatial changes in habitat productivity and heterogeneity using regression analyses, and explored potential differences between seasons of those responses. Furthermore, we used Mantel tests to examine the relationship between species composition similarity and both the environmental similarity between sites and the geographic distance between sites, also assessing differences between seasons in those relationships. Richness of insectivorous birds was directly related to primary productivity in both seasons, whereas richness of seed‐eaters showed a positive association with habitat heterogeneity during the spring. Species composition similarity between assemblages was correlated with both productivity similarity and geographic proximity during the autumn and the spring, except for insectivore assemblages. Diversity within main trophic groups seemed to reflect differences in their spatial patterns as a response to changes between seasons in the spatial patterns of food resources. Our findings suggest that considering different seasons and functional groups in the analyses of diversity spatial pattern could contribute to better understand the determinants of biological diversity in temperate climates.     

Organisation of the hemisphere interaction in preschool children and in adults during mental speech production and speech perception

The main goal of this study was to investigate reorganisation of the EEG systemic interactions spatial structure during mental speech production in preschool children: generating sentences from the set of words and generating words from the set of phonemes. In both cases, interhemisphere biopotential relations significantly increased as compared with the baseline (resting with closed eyes). Results of the EEG cross-correlation and coherent analyses showed that during verbal tasks marked intensification of hemisphere interaction was observed. High coefficients of statistic similarity between intercortical interactions patterns in adults and children during sentence and words generating were observed (SC = 0.71 & 0.62 respectively). Opposite to that, lesser coefficients of statistic similarity were observed between these two groups during grammar and semantic mistakes identification (SC < or = 0.50). According to this data we could expect a relatively high maturation level of central mechanisms which underlie the processes of speech production rather than mechanisms which underlie grammar and semantic mistakes identification in preschool children.     

Can resource use be the link between productivity and species richness in mammals?

Species richness has been shown to be affected by primary productivity at various spatial scales. However, the mechanisms behind this effect are still poorly understood. Under the assumption that primary productivity is directly related to energy availability for an animal assemblage, the hypotheses are that (i) primary productivity will affect the number of ways different food resources can be combined into species specific niches and (ii) it will also determine the number of specialist species that can be supported. These hypotheses were tested on the herbivorous mammalian fauna of Australia. Productivity only had a weak effect on the number of food resource combinations in this case. Specialization was most common at low and high productivity. In addition there were significant differences in where different types of specialization was the most common. This study seeks an energetic mechanism to explain an energetic relationship and though no clear effect was found for resource use it identified a possible link between productivity and species richness.     

The influence of visual imagery experience on EEG spatial organization

The comparison of EEG spatial organization between groups of 23 students of graphic arts department ("professional" subjects) and 39 subjects of another specialization ("non-professional" subjects) was made in order to find EEG correlates of visual imagery experience. Changes in the spatial organization of biopotentials (spatial synchronization and spatial disorder, spectral power and coherence) were analyzed while subjects mentally composed visual images from two simple elements, right angle and oblique line. The total number of elements presented for the image composition increased with each subsequent task (in total, four tasks were presented) from the number adequate to simultaneous perception and conscious processing (less than 7 +/- 2) to a much higher number. Intergroup differences, especially, in the degree of the spatial disorder (non-linear processes), were most evident under conditions when the subjects operated with a greater number of elements (tasks 3 and 4). This parameter increased more rapidly in "professionals" than in "non-professionals". These changes were most pronounced in the right anterior cortex. In "non-professional" subjects, spatial synchronization (linear processes) increased in the right posterior area. In "professional" subjects, coherence and spectral power increased in a greater number of narrow EEG frequency subbands than in "non-professional" subjects. The findings suggest that the imagery performance in subjects with visual imagery experience involves complicated neurodynamic processes such as non-linear dynamics and numerous EEG spatial resonance systems.     

Variation in nutrient characteristics of surface soils from the Luquillo Experimental Forest of Puerto Rico: A multivariate perspective

We assessed the effects of landscape features (vegetation type and topography), season, and spatial hierarchy on the nutrient content of surface soils in the Luquillo Experimental Forest (LEF) of Puerto Rico. Considerable spatial variation characterized the soils of the LEF, and differences between replicate sites within each combination of vegetation type (tabonuco vs. palo colorado vs. dwarf vs. pasture) and topographic position (ridge vs valley) accounted for 11–60% of the total variation in soil properties. Nevertheless, mean soil properties differed significantly among vegetation types, between topographic positions, and between seasons (wet vs dry). Differences among vegetation types reflected soil properties (e.g., bulk density, soil moisture, Na, P, C, N, S) that typically are related to biological processes and inputs of water. In forests, differences between topographic positions reflected elements (e.g., Ca, Mg, K, and Al) that typically are associated with geochemical processes; however, the nutrients and elements responsible for topographic differences in dwarf forest were different from those in other forest types. In pastures, differences between topographic positions were associated with the same soil properties responsible for differences among the other vegetation types. Pastures also had reduced N levels and different soil characteristics compared to undisturbed tabonuco forest. The only soil parameter that differed significantly between seasons was soil moisture. Soils of the LEF do not support the contention that N becomes limiting with an increase in elevation, and suggest that absolute pool sizes of N and P are not responsible for the reduction in productivity with elevation.     

Comparative analysis of EEG spatial organization in the rats with different level of genetically determinated anxiety under ethanol

The pecularities of EEG changes in the rats with geneticaly different level of anxiety was studed after ethanol injection. The biopotentials spatial synchronization and entropy in the "high anxious" rats (strain MR) did not increase under low dose; on the contrary the above changes were characteristic for the rats without anxiety signs (strain MNRA). After injection of middle and high ethanol doses the "high anxious" rats as compared with "low anxious" ones had the "simplification" of reaction type--the increase of narrow frequency coherence (i.e. linear biopotentials relationship) and spectral power of theta-activity (5.75-7.25 Hz), which was combined with the decrease of nonlinear biopotential characteristics. This fact is interpreted as the predominance of subcortical mechanisms of the brain functional state regulation over cortical ones. The significant decrease of high frequency EEG components in "high anxious" rats takes place under more high ethanol doses, presumably reflecting the increase of the anxiolytic level of ethanol effect.     

Strategy and results: Sex differences in electrographic correlates of verbal and figural creativity

Sex differences in electroencephalographic (EEG) correlates of creativity were studied using verbal and figural divergent tasks to be performed in accordance with the instructions to “give any solution” or “give an original solution.” The common effect was a greater activity of the right hemisphere, which did not depend on the sex, task type, or instructions for performance of the tasks. The α₂ and β₂ rhythms were the main EEG frequency correlates of creative thinking; the degree and sign of their reactivity depended on the aforementioned factors. Although the creative abilities in men and women were similar under test conditions, the EEG correlates of both figural and verbal tasks were sex-dependent. A high reactivity of the α₂ rhythm was more marked during verbal creative thinking in women; and that of the β₂ rhythm, during figural creative thinking in men. The instruction-related improvement of the critical selection of solutions was to a greater extent reflected by changes in the cortical activity, more pronounced in the frontal cortex in the women. Thus, the same creative productivity in men and women was mediated by different strategies of performance of both figural and verbal tasks, and the sex-related differences in these strategies remained even when the motivation for creativity was changed.     

高寒草甸不同草地类型功能群多样性及组成对植物群落生产力的影响

对不同类型草地功能群多样性和组成与植物群落生产力之间的关系进行了探讨。结果表明：(1)在矮嵩草(Kobresia humlis)草甸和金露梅(Potentilla froticosa)灌丛中,豆科植物的作用比较明显,而其他功能群植物的作用较弱。(2)在藏嵩草(Kobresia tibetica)沼泽化草甸和小嵩草(K．pygmaca)草甸中,虽然杂类草、C3植物和莎草科植物功能群的生产力占群落初级生产力的比例较大,但二者在统计上没有显著性差异,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响,更主要的是受到功能群内物种密度和均匀度的影响,即功能群组成比功能群多样性更能说明对生态系统过程的影响。(3)不同类型草地群落植物功能群盖度与群落初级生产力呈显著的线性相关。(4)不同类型草地群落生产力与功能群内物种数的变化均表现为单峰曲线关系,即功能群内物种数处于中间水平时,群落生产力最高。     

Discrimination of Image Orientation in the Presence of Distractors

We studied the influence of additional images (distractors) on the recognition of test objects, which included low-contrast Landolt circles with sizes of 1.1, 1.5, and 2.2 angular degrees and were presented eccentrically at 13.2 degrees from fixation. The distractors were either Landolt Cs or full circles with the same spatial characteristics. The distance between the test objects and the distractors varied from 2.2 to 24.2 angular degrees. The subjects were required to report the orientation of the tests (simple task) or to report the orientation of the tests and the shape of the distractor (dual task). The first group of subjects performed both simple and dual tasks, while the second group only performed the simple task. A significant deterioration of performance was recorded at all tested separations in both tasks; it was more pronounced in the dual task. The percent of correct responses was lower when Landolt circles were distractors as compared with full circles. The subjects tended to report the orientation of the distractors instead of tests in the cases of small and large separations. The recognition of distractors was also performed at a lower level in the cases of small and large distances. The data show that attention contributes to the task performance in two ways: the features of tests and distractors are integrated, or the tests are substituted by distractors.     

Structure of communities of ground-dwelling animals at the junction of two phytogeographic zones

Changes in the structure of tenebrionid beetle, lizard and rodent communities along the aridity gradient that determines the position of a phytogeographic province boundary were studied to test: (1) whether there are two different species assemblages on either side of the boundary (2) the extent of their differentiation and (3) if they are composed of different or the same faunal elements. Several ordination methods were tested for their capacity to reflect community structure, and discriminant function analysis was selected as the primary method of ordination. Each of the ordination axes reflected a complex environmental gradient. The latter was different for each taxon. The gradient of productivity cross-cuts ecological space for each animal group in an individual manner. Revealed spatial assemblages of species were related to the level of productivity. There was one assemblage of species at high productivity and one or two assemblages occurred at low productivity in each taxon. The α–diversity curve of rodents changed weakly along the productivity gradient, whereas those of lizard and beetle communities were distinctly unimodal and had maxima near the middle of the gradient. β–diversity curves of rodents had a concave shape, but those of lizard and beetle communities increased from low productivity values to the middle of the gradient and after that weakly declined to the upper (productive) end of the gradient. Seven types of ranges or areographic groups of species were distinguished. Each species assemblage was composed of different faunal elements. Comparison of the results of ecological and areographic analyses demonstrated that two assemblages of rodents and lizards represent different guilds within the same community rather than different communities. The phytogeographic border for these taxa is an ecological rather than a geographical boundary. The difference between the two tenebrionid assemblages appears to be zoogeographical rather than ecological, and coincides with the phytogeographic boundary.     

Sex differences and bilateral electrodermal activity: a replication

The present study was aimed at replicating the results of a previous work on sex differences and electrodermal asymmetry from our laboratory (Román, et al. 1987). Skin conductance was bilaterally recorded in a sample of 44 dextral volunteers (22 males and 22 females) during a stimulus-free period, and the performance of two tasks (verbal and spatial). Subjects were grouped into two groups of right-hand and left-hand dominance in their electrodermal responses (EDRs) in accordance with their laterality coefficient scores at rest. During the tasks subjects appeared clearly differentiated by their lateralization in the magnitude and frequency of EDRs independently of gender: right-hand responders showed higher electrodermal activity on their right hand, while left-hand responders showed higher electrodermal activity on their left hand. Sex differences were not observed within each responsiveness pattern. The orientation of phasic electrodermal changes remained constant throughout the different conditions.     

Tactile perception and manual dexterity in computer users

Recent studies suggest that sensory input generated during highly repetitive tasks can degrade the sensory representation of the hand and eventually lead to sensory and motor problems. In this study, we investigated whether early changes in tactile perception and manual dexterity could be detected in persons exposed to computer tasks. Performance in tests designed to assess tactile perception (grating orientation task for spatial acuity and roughness discrimination) and manual dexterity (grooved pegboard test) was compared between two groups of healthy individuals, matched for age, gender, and experience, who differed in terms of computer habits. One group consisted of frequent users (FU, > 2 h/day, n = 36) and the other of non or occasional users (OU, < 2 h/day, n = 28). Comparison of performance between groups with subjects sorted by gender revealed significant differences ( t -test, p < 0.05) in female, but not male, participants. Grating resolution thresholds at the tip on the second and fifth digits were, on average, 40% higher in female FU ( n = 13) than in female OU ( n = 10) and performance scores on the dexterity test were significantly higher for the left hand. The results of this study indicate that early signs of deterioration in hand function can be present in persons constantly exposed to computer tasks and that these signs are more readily apparent in women than in men. The loss of tactile spatial acuity found in female FU possibly reflect an early consequence of the degraded sensory representation of the hand resulting from constant repetitions of fine motor tasks.