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Journal articles on the topic 'Hemispheres'
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1
Friedrich, Patrick, Kaustubh R. Patil, Lisa N. Mochalski, Xuan Li, Julia A. Camilleri, Jean-Philippe Kröll, Lisa Wiersch, Simon B. Eickhoff, and Susanne Weis. "Is it left or is it right? A classification approach for investigating hemispheric differences in low and high dimensionality." Brain Structure and Function 227, no. 2 (December 9, 2021): 425–40. http://dx.doi.org/10.1007/s00429-021-02418-1.
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AbstractHemispheric asymmetries, i.e., differences between the two halves of the brain, have extensively been studied with respect to both structure and function. Commonly employed pairwise comparisons between left and right are suitable for finding differences between the hemispheres, but they come with several caveats when assessing multiple asymmetries. What is more, they are not designed for identifying the characterizing features of each hemisphere. Here, we present a novel data-driven framework—based on machine learning-based classification—for identifying the characterizing features that underlie hemispheric differences. Using voxel-based morphometry data from two different samples (n = 226, n = 216), we separated the hemispheres along the midline and used two different pipelines: First, for investigating global differences, we embedded the hemispheres into a two-dimensional space and applied a classifier to assess if the hemispheres are distinguishable in their low-dimensional representation. Second, to investigate which voxels show systematic hemispheric differences, we employed two classification approaches promoting feature selection in high dimensions. The two hemispheres were accurately classifiable in both their low-dimensional (accuracies: dataset 1 = 0.838; dataset 2 = 0.850) and high-dimensional (accuracies: dataset 1 = 0.966; dataset 2 = 0.959) representations. In low dimensions, classification of the right hemisphere showed higher precision (dataset 1 = 0.862; dataset 2 = 0.894) compared to the left hemisphere (dataset 1 = 0.818; dataset 2 = 0.816). A feature selection algorithm in the high-dimensional analysis identified voxels that most contribute to accurate classification. In addition, the map of contributing voxels showed a better overlap with moderate to highly lateralized voxels, whereas conventional t test with threshold-free cluster enhancement best resembled the LQ map at lower thresholds. Both the low- and high-dimensional classifiers were capable of identifying the hemispheres in subsamples of the datasets, such as males, females, right-handed, or non-right-handed participants. Our study indicates that hemisphere classification is capable of identifying the hemisphere in their low- and high-dimensional representation as well as delineating brain asymmetries. The concept of hemisphere classifiability thus allows a change in perspective, from asking what differs between the hemispheres towards focusing on the features needed to identify the left and right hemispheres. Taking this perspective on hemispheric differences may contribute to our understanding of what makes each hemisphere special.
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Hsiao, Janet H., Ben Cipollini, and Garrison W. Cottrell. "Hemispheric Asymmetry in Perception: A Differential Encoding Account." Journal of Cognitive Neuroscience 25, no. 7 (July 2013): 998–1007. http://dx.doi.org/10.1162/jocn_a_00377.
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Hemispheric asymmetry in the processing of local and global features has been argued to originate from differences in frequency filtering in the two hemispheres, with little neurophysiological support. Here we test the hypothesis that this asymmetry takes place at an encoding stage beyond the sensory level, due to asymmetries in anatomical connections within each hemisphere. We use two simple encoding networks with differential connection structures as models of differential encoding in the two hemispheres based on a hypothesized generalization of neuroanatomical evidence from the auditory modality to the visual modality: The connection structure between columns is more distal in the language areas of the left hemisphere and more local in the homotopic regions in the right hemisphere. We show that both processing differences and differential frequency filtering can arise naturally in this neurocomputational model with neuroanatomically inspired differences in connection structures within the two model hemispheres, suggesting that hemispheric asymmetry in the processing of local and global features may be due to hemispheric asymmetry in connection structure rather than in frequency tuning.
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Miller, Michael B., Alan Kingstone, and Michael S. Gazzaniga. "Hemispheric Encoding Asymmetry is More Apparent Than Real." Journal of Cognitive Neuroscience 14, no. 5 (July 1, 2002): 702–8. http://dx.doi.org/10.1162/08989290260138609.
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Previous neuroimaging studies have claimed a left hemisphere specialization for episodic “encoding” and a right hemisphere specialization for episodic “retrieval.” Yet studies of split-brain patients indicate relatively minor memory impairment after disconnection of the two hemispheres. This suggests that both hemispheres are capable of encoding and retrieval. In the present experiment, we examined the possible limits on encoding capacity of each hemisphere by manipulating the “depth” of processing during the encoding of unfamiliar faces and familiar words in the left and right hemispheres of two split-brain patients. Results showed that only the left hemisphere benefited from deeper (more elaborate) encoding of familiar words, and only the right hemisphere benefited from deeper encoding of unfamiliar faces. Our findings are consistent with the view that hemispheric asymmetries in episodic encoding are related to hemisphere-specific processing of particular stimuli. Convergent with recent neuroimaging studies, these results with split-brain patients also suggest that these hemispheric differences are not due to unique specializations in each half brain for encoding memories, but rather, are due to preferential recruitment of the synaptically closer prefrontal cortex to posterior regions processing material-specific information.
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Chowdhury, Partha, Ravindra Belur, Luca Bertello, and Alexei A. Pevtsov. "Analysis of Solar Hemispheric Chromosphere Properties using the Kodaikanal Observatory Ca–K Index." Astrophysical Journal 925, no. 1 (January 1, 2022): 81. http://dx.doi.org/10.3847/1538-4357/ac3983.
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Abstract The Kodaikanal Observatory has provided long-term synoptic observations of chromospheric activities in the Ca ii K line (393.34 nm) since 1907. This article investigates temporal and periodic variations of the hemispheric Ca–K-index time series in the low-latitude zone (±40°), utilizing the recently digitized photographic plates of Ca–K images from the Kodaikanal Observatory for the period of 1907–1980. We find that the temporal evolution of the Ca–K index differs from one hemisphere to another, with the solar cycle peaking at different times in the opposite hemisphere, except for cycles 14, 15, and 21, when the phase difference between the two hemispheres was not significant. The monthly averaged data show a higher activity in the northern hemisphere during solar cycles 15, 16, 18, 19, and 20, and in the southern hemisphere during cycles 14, 17, and 21. We notice an exponentially decaying distribution for each hemisphere’s Ca–K index and the whole solar disk. We explored different midterm periodicities of the measured Ca–K index using the wavelet technique, including Rieger-type and quasi-biennial oscillations on different timescales present in the time series. We find a clear manifestation of the Waldmeier effect (stronger cycles rise faster than the weaker ones) in both the hemispheres separately and the whole disk in the data. Finally, we have found the presence of the Gnevyshev gap (time interval between two cycle maxmima) in both the hemispheric data during cycles 15 to 20. Possible interpretations of our findings are discussed with the help of existing theoretical models and observations.
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Baybakov, S. E., N. S. Bakhareva, S. V. Chigrin, E. K. Gordeeva, T. R. Yusupov, E. A. Salomatina, and D. D. Shevchuk. "Hemispheric Asymmetry Gender Differences in Preadolescent Children." Innovative Medicine of Kuban, no. 1 (March 6, 2023): 53–57. http://dx.doi.org/10.35401/2541-9897-2023-26-1-53-57.
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Background: Investigating various postnatal parameters of cerebral hemispheres is of great practical value.Objective: To study gender differences in hemispheric parameters and interhemispheric interactions in preadolescent children.Materials and methods: The retrospective study assessed archived brain magnetic resonance images of 60 eight-year-old boys and 60 eight-year-old girls. The analyzed parameters were as follows: 1) hemispheric length; 2) hemispheric width; 3) hemispheric height; 4) width-longitudinal index of a hemisphere; 5) altitude-longitudinal index of a hemisphere; 6) length of frontal lobes; 7) length of parietal lobes; 8) length of occipital lobes; 9) length of temporal lobes. Quantitative indicators were assessed for normal distribution using the Kolmogorov–Smirnov test. Source data were accumulated and arranged in Microsoft Excel 2016 spreadsheets. Statistica 10.0 was used for the statistical analysis. The results were considered statistically significant with P < 0.05.Results: The analysis of cephalometric indicators suggests sex-related variation in the cerebral hemispheres. Based on the obtained data we can identify morphometric parameters of interhemispheric variability that may act as one of the morphometric criteria for the brain asymmetry. The study results can be widely used for neuroimaging.Conclusions: We determined cephalometric reference values for various cerebral hemispheres parts in preadolescent children.
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Cronin-Golomb, Alice. "Semantic Networks in the Divided Cerebral Hemispheres." Psychological Science 6, no. 4 (July 1995): 212–18. http://dx.doi.org/10.1111/j.1467-9280.1995.tb00595.x.
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Hemispheric differences in the recognition and manipulation of meaning may be based on distinctions in size, composition, or organization of the right and left semantic networks The present study describes these features of pictorially based semantic networks in 3 subjects with complete forebrain commissurotomy Stimuli were presented for prolonged viewing to the left and right visual hemifields For each trial, the subjects chose from a 20-choice array all pictures that were associated with a target, then indicated the member of each pair of chosen associates that was more closely related to the target The hemispheres' networks were found to be of similar size and composition, but were organized differently The right hemisphere more often produced linear rankings of semantic associates to a target than did the left, and rankings by the two hemispheres were not strongly correlated Hemispheric differences in semantic organization mirror differences in perceptual organization, with the right hemisphere specialized for conventional meaning and the left hemisphere specialized for detecting and processing deviations from standard meaning
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Trach, О. О., D. M. Shyian, and D. I. Marakushin. "Individual variability of the brain hemispheres’ and occipital lobes’ width." Medicine Today and Tomorrow 88, no. 3 (October 1, 2020): 4–11. http://dx.doi.org/10.35339/msz.2020.88.03.01.
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200 hemispheres of the brain of people who died from diseases not related to brain pathology were studied. Morphometric method was used and statistical analysis was completed. It was found out that the width of the right and left hemispheres of the brain in both men and women of brachycranial skull type is slightly greater than of mesocranial and dolichocranial ones. Men and women with dolichocranial skull type have the width of the left hemisphere greater than the right one. Men have the width of the left and right hemispheres greater than women. The limits of individual variability of brain hemispheres’ and occipital lobes’ width have been determined taking into account the type of skull and sex. The largest indicators of the cerebral hemispheres’ width are the next: men of the brachycranial skull type have the right hemisphere’s width of the 70.6•10^-3 m, left one of the 71.4•10^3 m width; the women of the brachycranial skull type have the right hemispheres’ width of the 63.4•10^-3 m and the left one of the 63.8•10^3 m, the women of the mesocranial skull type have the left hemisphere’s width of 63.7•10^3 m. The smallest indicators of the cerebral hemispheres’ width are: men of the dolichocranial skull type have the width of the right hemisphere 44•10^3 m, of the left one of the dolichocranial skull type and of the brachycranial skull type have the width 43.8•10^3 m; women of the dolichocranial skull type have the width of the right hemisphere 38.5•10^3 m, left one of 42.5•10^-3. The largest indicators of the occipital lobes’ width are: men of the brachycranial skull type have the width of the right hemisphere 56•10^3 m, men of the mesocranial skull type have the width of the left hemisphere 65•10^3 m; women of the dolichocranial skull type have the right hemispheres’ width 58•10^-3 m, of mesocranial skull type have the left one is of 63•10^-3 m and of dolichocranial it is of 62.5•10^3 m. The smallest indicators of the occipital lobes’ width are: men of the dolichocranial skull type have the width of the right lobe 41•10^3 m, of mesocranial and brachycranial types it is 42•10^3 m, the width of the left lobe in men with dolichocranial skull type of 38•10^3 m; women of the mesocranial skull type have the right lobe’s width of 36•10^3 m, the left one of dolichocranial skull type it is of 34•10^-3 m. Keywords: endbrain, occipital lobe, individual anatomical variability.
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Doty, Robert. "Unity from duality." Acta Neurobiologiae Experimentalis 63, no. 3 (September 30, 2003): 163–70. http://dx.doi.org/10.55782/ane-2003-1464.
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When, in the primeval sea, creatures first began to crawl, "right" and "left" came into being, yielding neuronal nets to control response to the sidedness of stimuli. In the half billion years of moving and sensing, two brains have evolved, the right and the left; and human experience now shows them to be roughly equivalent, potentially independent, conscious entities. This dramatic fact is evidenced by "split-brain" patients and by numerous cases of therapeutic removal of either hemisphere. Equally dramatic, of course, is that there is not the slightest sign of this duality in everyday experience, the right and left visual fields are seamlessly knit, and cross purpose is absent in the moment to moment operation of the two cerebral hemispheres. This unity is constantly synthesized by the 100,000,000 fibers passing from each hemisphere to the other; the vastness of that interchange emphasized upon comparison with the mere 1,000,000 fibers conveying all the visual world from each eye. With the large distances in the human brain some 100+ ms may commonly transpire for one hemisphere to send to and receive a response from the other. Efficiency thus demands that most neuronal calculation occur within rather than between hemispheres, thereby promoting differences in the characteristic capabilities of each alone, i.e., "hemispheric specialization". Despite this there is a bewildering bilaterality of activation revealed by fMRI for most cognitive tasks. In the absence of the forebrain commissures brainstem systems can be shown, in macaques, also to participate in the unification of behavioral result from the actions of the separated hemispheres. The system favors synthesis from congruent (visual) input to the two hemispheres; but in the face of incompatible hemispheric input, the two hemispheres are able to work out an accommodation in their control of subcortical systems.
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Schwartz, Theodore H., Michael M. Haglund, Ettore Lettich, and George A. Ojemann. "Asymmetry of Neuronal Activity During Extracellular Microelectrode Recording from Left and Right Human Temporal Lobe Neocortex During Rhyming and Line-Matching." Journal of Cognitive Neuroscience 12, no. 5 (September 2000): 803–12. http://dx.doi.org/10.1162/089892900562615.
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Recordings of neuronal activity in humans have identified few correlates of the known hemispheric asymmetries of functional lateralization. Here, we examine single-unit activity recorded from both hemispheres during two delayed match-to-sample tasks that show strong hemispheric lateralization based on lesion effects; a line-matching (LM) task related to the right hemisphere, and a rhyming (RHY) task related to the left. Nineteen neuronal populations were recorded with extracellular microelectrodes from the left temporal neocortex of 11 awake patients, and 18 from the right in 9 patients during anterior temporal lobectomy for complex partial seizures under local anesthesia. All subjects were left hemisphere dominant for language. Twelve (32%) populations exhibited statistically significant changes in activity at p < .05. Although changes in firing frequency were recorded from both hemispheres during both tasks, the RHY task elicited changes in activity several hundred milliseconds earlier on the left side than on the right. The LM task, on the other hand, induced changes earlier on the right side than on the left. Both hemispheres contained units active during verbal responses regardless of which behavior elicited the response. Our results indicate that cerebral dominance is reflected in earlier neuronal activity in the anterior temporal lobe during tasks lateralized to that hemisphere.
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Deng, L. H., Y. Fei, H. Deng, Y. Mei, and F. Wang. "Spatial distribution of quasi-biennial oscillations in high-latitude solar activity." Monthly Notices of the Royal Astronomical Society 494, no. 4 (May 6, 2020): 4930–38. http://dx.doi.org/10.1093/mnras/staa1061.
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ABSTRACT Quasi-biennial oscillations (QBOs) are considered to be a fundamental mode of solar magnetic activity at low latitudes (≤50°). However, the evolutionary aspect and the hemispheric distribution of solar QBOs at high latitudes (≥60°) are rarely studied. Here, we apply a relatively novel time-frequency analysis technique, called the synchrosqueezed wavelet transform, in order to extract the main components of the polar faculae in the Northern and Southern hemispheres for the time interval from 1951 August to 1998 December. We note the following. (i) Apart from the 22-yr Hale cycle, the 17-yr extended activity cycle and the 11-yr Schwabe cycle, QBOs have been estimated as a prominent time-scale of solar magnetic activity at high latitudes. (ii) The QBOs of the polar faculae are coherent in the two hemispheres, but the temporal (phase) and the spatial (amplitude) variations of solar QBOs occur unevenly on both hemispheres. (iii) For the 11-yr period mode, this begins in the Northern hemisphere three months earlier than in the Southern hemisphere. Moreover, the spatial and temporal distributions of the hemispheric QBOs differ from those of the 11-yr Schwabe cycle mode in the two hemispheres. Our findings could be helpful to improve our knowledge of the physical origin of the spatial distribution of solar QBOs at high latitudes, and could also provide more constraints on solar dynamo models introduced to characterize the different components of the solar magnetic activity cycle.
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Trushina, D. A., O. A. Vedyasova, and M. A. Paramonova. "SPATIAL PICTURE OF DISTRIBUTION OF ELECTROENCEPHALOGRAM RHYTHMS IN THE RIGHT-HANDED STUDENTS DURING AN EXAM." Vestnik of Samara University. Natural Science Series 20, no. 3 (May 31, 2017): 202–12. http://dx.doi.org/10.18287/2541-7525-2014-20-3-202-212.
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Registration of electroencephalogram (EEG) in the right-handed students during an exam revealed weakening of alpha rhythm in all areas of right and left cerebral hemispheres as well as increased beta rhythm in parietal and end-lobes of the right hemisphere. Simultaneously regular delta waves in the frontal leads ofboth hemispheres and theta waves in right frontal, occipitalis and temporal leads were marked. Offset of EEG slow wave activity in the right hemisphere in partial right-handers was marked in more noticeable way than in that of the true right-handers. The obtained data suggest that the distribution of EEG rhythms in condition of mental and emotional stress in right-handers depends on the type and severity of functional hemispheric asymmetry.
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Voigt, Aiko, Bjorn Stevens, Jürgen Bader, and Thorsten Mauritsen. "The Observed Hemispheric Symmetry in Reflected Shortwave Irradiance." Journal of Climate 26, no. 2 (January 15, 2013): 468–77. http://dx.doi.org/10.1175/jcli-d-12-00132.1.
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Abstract While the concentration of landmasses and atmospheric aerosols on the Northern Hemisphere suggests that the Northern Hemisphere is brighter than the Southern Hemisphere, satellite measurements of top-of-atmosphere irradiances found that both hemispheres reflect nearly the same amount of shortwave irradiance. Here, the authors document that the most precise and accurate observation, the energy balanced and filled dataset of the Clouds and the Earth’s Radiant Energy System covering the period 2000–10, measures an absolute hemispheric difference in reflected shortwave irradiance of 0.1 W m−2. In contrast, the longwave irradiance of the two hemispheres differs by more than 1 W m−2, indicating that the observed climate system exhibits hemispheric symmetry in reflected shortwave irradiance but not in longwave irradiance. The authors devise a variety of methods to estimate the spatial degrees of freedom of the time-mean reflected shortwave irradiance. These are used to show that the hemispheric symmetry in reflected shortwave irradiance is a nontrivial property of the Earth system in the sense that most partitionings of Earth into two random halves do not exhibit hemispheric symmetry in reflected shortwave irradiance. Climate models generally do not reproduce the observed hemispheric symmetry, which the authors interpret as further evidence that the symmetry is nontrivial. While the authors cannot rule out that the observed hemispheric symmetry in reflected shortwave irradiance is accidental, their results motivate a search for mechanisms that minimize hemispheric differences in reflected shortwave irradiance and planetary albedo.
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Hugdahl, Kenneth, and René Westerhausen. "What Is Left Is Right." European Psychologist 14, no. 1 (January 2009): 78–89. http://dx.doi.org/10.1027/1016-9040.14.1.78.
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The present paper is based on a talk on hemispheric asymmetry given by Kenneth Hugdahl at the Xth European Congress of Psychology, Praha July 2007. Here, we propose that hemispheric asymmetry evolved because of a left hemisphere speech processing specialization. The evolution of speech and the need for air-based communication necessitated division of labor between the hemispheres in order to avoid having duplicate copies in both hemispheres that would increase processing redundancy. It is argued that the neuronal basis of this labor division is the structural asymmetry observed in the peri-Sylvian region in the posterior part of the temporal lobe, with a left larger than right planum temporale area. This is the only example where a structural, or anatomical, asymmetry matches a corresponding functional asymmetry. The increase in gray matter volume in the left planum temporale area corresponds to a functional asymmetry of speech processing, as indexed from both behavioral, dichotic listening, and functional neuroimaging studies. The functional anatomy of the corpus callosum also supports such a view, with regional specificity of information transfer between the hemispheres.
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Rebai, Mohamed, Luciano Mecacci, Jean-Didier Bagot, and Claude Bonnet. "Hemispheric Asymmetries in the Visual Evoked Potentials to Temporal Frequency: Preliminary Evidence." Perception 15, no. 5 (October 1986): 589–94. http://dx.doi.org/10.1068/p150589.
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Steady-state evoked potentials were recorded in eight adult subjects from occipital and temporal leads of both hemispheres to investigate the effect of temporal frequency on the hemispheric specialization for basic visual information. A 3 cycles deg−1 grating was phase-reversed at different temporal frequencies (from 4 to 18 Hz), and the frequency spectrum of evoked potentials was computed by means of a fast Fourier transform program. Significant results were obtained for the component at twice the temporal frequency of stimulation. Occipital evoked potentials did not show hemispheric asymmetry, whereas temporal evoked potentials showed an interaction between hemisphere and temporal frequency: right and left hemispheres were respectively prominent for low (4 and 6 Hz) and for high (8–18 Hz) temporal frequencies. The results are discussed in the context of current research on hemispheric specialization for basic spatiotemporal parameters of visual information processing.
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Nikolaenko, N. N., A. Y. Egorov, and E. A. Freiman. "Representation Activity of The Right and Left Hemispheres of the Brain." Behavioural Neurology 10, no. 2-3 (1997): 49–59. http://dx.doi.org/10.1155/1997/101703.
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Drawings by psychiatric patients were studied in various states (i) in depression; (ii) after neuroleptic injection; and (iii) during left hemisphere suppression induced by unilateral electroconvulsive seizure (UES). In these states, right hemisphere activation predominates. The results of the study demonstrate that, under the predominance of right hemisphere activation over the left hemisphere, there is a tendency to reproduce the image of the object and to represent it in near space. Drawings by psychiatric patients were also investigated in (i) the manic state; (ii) after injection of psychotropic drugs which improved the mood; and (iii) during right hemisphere suppression following right-sided UES. Under these conditions, left hemisphere activation predominates and the drawings loose the illusion of three-dimensional space. A tendency to reproduce the knowledge and the ideas of the object and to represent it in distant space was observed. Thus, both hemispheres may represent space and elaborate perceptive and conceptional models of the world in different ways. It is probable that different types of representation are based on global (right-hemispheric) in comparison with focal (left-hemispheric) attention to space.
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Shibahara, Naoki, and Brennis Lucero-Wagoner. "Hemispheric Asymmetry in Accessing Word Meanings: Concrete and Abstract Nouns." Perceptual and Motor Skills 94, no. 3_suppl (June 2002): 1292–300. http://dx.doi.org/10.2466/pms.2002.94.3c.1292.
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The present experiments investigated hemispheric differences in the brain in accessing concrete and abstract word meanings. For this purpose, an automatic semantic priming paradigm was used with a short stimulus onset asynchrony between prime and target (250 msec.) as well as a low proportion of related trials. (20%). Analysis showed that for concrete nouns, priming effects were observed in both hemispheres. There was greater priming in the right hemisphere, suggesting hemispheric differences in accessing semantic representations of concrete nouns. For abstract nouns, on the other hand, priming patterns in the right hemisphere were identical to those in the left hemisphere, suggesting that information about abstract nouns projected to the right hemisphere may be transferred to the dominant left hemisphere for further processing.
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Veldema, Jitka, Dennis Alexander Nowak, Kathrin Bösl, and Alireza Gharabaghi. "Hemispheric Differences of 1 Hz rTMS over Motor and Premotor Cortex in Modulation of Neural Processing and Hand Function." Brain Sciences 13, no. 5 (May 2, 2023): 752. http://dx.doi.org/10.3390/brainsci13050752.
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Introduction: Non-invasive brain stimulation can modulate both neural processing and behavioral performance. Its effects may be influenced by the stimulated area and hemisphere. In this study (EC no. 09083), repetitive transcranial magnetic stimulation (rTMS) was applied to the primary motor cortex (M1) or dorsal premotor cortex (dPMC) of either the right or left hemisphere, while evaluating cortical neurophysiology and hand function. Methods: Fifteen healthy subjects participated in this placebo-controlled crossover study. Four sessions of real 1 Hz rTMS (110% of rMT, 900 pulses) over (i) left M1, (ii) right M1, (iii) left dPMC, (iv) right dPMC, and one session of (v) placebo 1 Hz rTMS (0% of rMT, 900 pulses) over the left M1 were applied in randomized order. Motor function of both hands (Jebsen–Taylor Hand Function Test (JTHFT)) and neural processing within both hemispheres (motor evoked potentials (MEPs), cortical silent period (CSP), and ipsilateral silent period (ISP)) were evaluated prior and after each intervention session. Results: A lengthening of CSP and ISP durations within the right hemisphere was induced by 1 Hz rTMS over both areas and hemispheres. No such intervention-induced neurophysiological changes were detected within the left hemisphere. Regarding JTHFT and MEP, no intervention-induced changes ensued. Changes of hand function correlated with neurophysiological changes within both hemispheres, more often for the left than the right hand. Conclusions: Effects of 1 Hz rTMS can be better captured by neurophysiological than behavioral measures. Hemispheric differences need to be considered for this intervention.
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Lobel, Daniel S., Rex M. Swanda, and Miklos F. Losonczy. "Lateralized Visual-Field Inattention in Schizophrenia." Perceptual and Motor Skills 79, no. 1 (August 1994): 699–702. http://dx.doi.org/10.2466/pms.1994.79.1.699.
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Numerous studies have shown impaired verbal functioning in schizophrenic patients as compared with normals. The verbal deficits are generally attributed to damage of the left cerebral hemisphere. This attribution is based on literature which suggests that verbal processing is primarily mediated by the left hemisphere in right-handed humans. This study explored left-hemispheric integrity directly by assessing sustained attention in both the left and right hemispheres of 40 schizophrenic patients with the Weintraub Cancellation Tasks. Patients made significantly more errors of omission on the right visual field than on the left. These results are consistent with cognitive research in schizophrenia by demonstrating selective left-hemispheric impairment relative to right-hemispheric functioning.
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Kuznetsova, S. M., S. G. Mazur, and M. S. Egorova. "PATHOGENETIC FEATURES OF FUNCTIONAL STATE OF THE BRAIN AND CARDIAC CEREBRAL RELATIONSHIPS IN PATIENTS WITH ATHEROTHROMBOSIS AND CARDIOEMBOLIC STROKE." National Journal of Neurology 2, no. 18 (November 30, 2018): 39–50. http://dx.doi.org/10.61788/njn.v2i18.07.
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The article presents data on the effect of Mexicor in patients who underwent cardioembolic stroke. Thus, Mexicor improves cerebral hemodynamics in Posterior cerebral circulation and causes a reorganization of the structure of brain bioelectrical activity and the type of frequency-amplitude reorganization is determined by the hemispheric localization of the stroke, which may be due to different hemispheres connection with regulating mesencephalic structures and synchronizing diencephalic structures of the brain. In patients with localization of ischemic lesion in the right hemisphere, Mexicor statistically significantly increases the power in the range of α1-, α2-rhythms in the affected and intact hemispheres, which indicates the active influence of the drug on the synchronizing diencephalo-talamic structures of the brain. In patients with localization of ischemic lesion in the left hemisphere, Mexicor predominantly reduces power in the range of slow rhythms and in the range of β2 rhythms in the two hemispheres, which is caused by increased metabolic and functional activity of the mesencephalic stem brain structures. In patients undergoing cardioembolic stroke, Mexicor has a harmonizing effect on the bioelectrical activity of the brain, and improves cerebral hemodynamics, which gives grounds to recommend the use of Mexicor for the rehabilitation of patients who have undergone cardioembolic stroke.
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Yarosh, Oleg Aleksandrovich. "The role of neurotransmitter systems separate the hemispheres of the brain in action the new antiepileptic compounds AGB-31." Reviews on Clinical Pharmacology and Drug Therapy 11, no. 2 (June 15, 2013): 31–35. http://dx.doi.org/10.17816/rcf11231-35.
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Compound AGB-31, a monocarbamate derivative, is shown to possess a high antiepileptic activity. The mechanisms of antiepileptic action are connected with significant increase in glutamic acid decarboxylase activity in the left hemisphere of the brain, with trend of the glutamate content decrease in the left hemisphere and the tendency to increase GABA in both hemispheres. AGB-31 significantly (more than 3-fold) increases syntase nitric oxide activity in the left hemisphere and has a tendency to reduce the NO content in both hemispheres. AGB-31 significantly (by 63.4%), reduced glutathione peroxydase activity in the right hemisphere without changing it in the left, with a tendency to increase the activity of glutathione reductase in both hemispheres.
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Ravindra, Belur, Partha Chowdhury, Pratap Chandra Ray, and Kumaravel Pichamani. "Temporal Evolutions and Quasiperiodic Variations Present in the Sunspot Number and Group Sunspot Area Data Measured at Kodaikanal Observatory for Solar Cycles 14–24." Astrophysical Journal 940, no. 1 (November 1, 2022): 43. http://dx.doi.org/10.3847/1538-4357/ac98b3.
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Abstract The Kodaikanal Observatory has made synoptic observations of the Sun in white light since 1904, and these images are sketched on the Stonyhurst grids called Sun charts. These continuous hand-drawn data sets are used for long-term studies of the Sun. This article investigates temporal and periodic variations of the monthly hemispheric sunspot number and sunspot group area for 1905–2016, covering solar cycles 14–24. We find that the temporal variations of the sunspot number and group area are different in each hemisphere and peak at different times of the solar cycle in the opposite hemisphere. For both data sets, Cycle 19 shows maximum amplitude. For the sunspot number time series, Cycle 24 was the weakest, and Cycle 15 for the group area. The existence of double peaks and violation of the “odd–even rule” was found in both data sets. We have studied the periodic and quasiperiodic variations in both time series using the wavelet technique. We noticed that, along with the fundamental mode of the ∼11 yr cycle and polarity reversal period of 22 yr, the sunspot activity data also exhibited several midterm periodicities in the opposite hemispheres, in particular the Rieger-group, and quasi-biennial periodicities. The temporal evolution of these detected quasi-periodicities also differs in the northern and southern hemispheres. We analyzed the data set statistically to understand the bulk properties and coupling between the opposite hemispheres. The study indicates that the two hemispheric data sets differ, but some dependency could be present.
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Ikkert, Oksana, and Tetiana Korol. "CEREBRAL HEMISPHERES FUNCTIONAL ASYMMETRY IN THE EDUCATION OF NATURAL SPECIALTIES AND HUMANITIES STUDENTS." Scientific Journal of Polonia University 58, no. 3 (September 1, 2023): 90–97. http://dx.doi.org/10.23856/5813.
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The functional asymmetry of the human brain hemispheres (motor, sensory and mental) reflects the difference in the distribution of neuropsychological functions between its right and left hemispheres. Both hemispheres are involved in the implementation of any types of mental activity or regulation of vegetative physiological processes, but each of them provides different aspects of this activity and some processes domination. Persons with left-hemisphere and right-hemisphere thinking differ in the features of perception, analysis, and reproduction of information, which is important in the process of students' educational activities. That is why the aim of this investigation was to conduct a comparative analysis of the types of the brain hemispheres dominance in students of natural and humanities education who study at the biological and philosophical faculties of the Ivan Franko National University of Lviv and proposed methodological approaches for development and activation both (left and right) brain hemispheres. Methods used in the study: determining the coefficient of functional asymmetry of the brain; general scientific (analysis and synthesis), methods of theoretical research (from abstract to concrete). It was shown that most of the student are dominated by the left brain hemisphere but organizing of the educational process needs to use methods of educational activities aimed at the development and activation both (left and right) brain hemispheres.
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Лунюшкин, Сергей, Sergey Lunyushkin, Владимир Мишин, Vladimir Mishin, Юрий Караваев, Yuriy Karavaev, Юрий Пенских, Yury Penskikh, Вячеслав Капустин, and Vyacheslav Kapustin. "Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm." Solar-Terrestrial Physics 5, no. 2 (June 28, 2019): 15–27. http://dx.doi.org/10.12737/stp-52201903.
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The magnetogram inversion technique (MIT), developed at ISTP SB RAS more than forty years ago, has been used until recently only in the Northern Hemisphere. In recent years, MIT has been improved and extended to make instantaneous calculations of 2D distributions of electric fields, horizontal and field-aligned currents in two polar ionospheres. The calculations were carried out based on one-minute ground-based geomagnetic measurements from the worldwide network of stations in both hemispheres (SuperMAG). In this paper, this extended technique is used in the approximation of uniform ionospheric conductance and is applied for the first time to calculations of equivalent and field-aligned currents in two hemispheres through the example of the August 17, 2001 geomagnetic storm. We have obtained the main and essential result: the advanced MIT-ISTP can calculate large-scale distributions of ionospheric convection and FACs in the Northern (N) and Southern (S) polar ionospheres with a high degree of expected hemispheric similarity between these distributions. Using the said event as an example, we have established that the equivalent and field-aligned currents obtained with the advanced technique exhibit the expected dynamics of auroral electrojets and polar caps in two hemispheres. Hall current intensities in polar caps and auroral electrojets, calculated from the equivalent current function, change fairly synchronously in the N and S hemispheres throughout the magnetic storm. Both (westward and eastward) electrojets of the N hemisphere are markedly more intense than respective electrojets of the S hemisphere, and the Hall current in the north polar cap is almost twice as intense as that in the south one. This interhemispheric asymmetry is likely to be due to seasonal conductance variations, which is implicitly contained in the current function. From FAC distributions we determine auroral oval boundaries and calculate magnetic fluxes through the polar caps in the N and S hemispheres. These magnetic fluxes coincide with an accuracy of about 5 % and change almost synchronously during the magnetic storm. In the N hemisphere, the magnetic flux in the dawn polar cap is more intense that that in the dusk one, and vice versa in the S hemisphere. These asymmetries (dawn–dusk and interhemispheric) in the polar caps are consistent with the theory of reconnection for IMF By>0 and with satellite images of auroral ovals; both of these asymmetries decrease during the substorm expansion phase.
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Лунюшкин, Сергей, Sergey Lunyushkin, Владимир Мишин, Vladimir Mishin, Юрий Караваев, Yuriy Karavaev, Юрий Пенских, Yury Penskikh, Вячеслав Капустин, and Vyacheslav Kapustin. "Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm." Solnechno-Zemnaya Fizika 5, no. 2 (June 28, 2019): 17–29. http://dx.doi.org/10.12737/szf-52201903.
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The magnetogram inversion technique (MIT), developed at ISTP SB RAS more than forty years ago, has been used until recently only in the Northern Hemisphere. In recent years, MIT has been improved and extended to make instantaneous calculations of 2D distributions of electric fields, horizontal and field-aligned currents in two polar ionospheres. The calculations were carried out based on one-minute ground-based geomagnetic measurements from the worldwide network of stations in both hemispheres (SuperMAG). In this paper, this extended technique is used in the approximation of uniform ionospheric conductance and is applied for the first time to calculations of equivalent and field-aligned currents in two hemispheres through the example of the August 17, 2001 geomagnetic storm. We have obtained the main and essential result: the advanced MIT-ISTP can calculate large-scale distributions of ionospheric convection and FACs in the Northern (N) and Southern (S) polar ionospheres with a high degree of expected hemispheric similarity between these distributions. Using the said event as an example, we have established that the equivalent and field-aligned currents obtained with the advanced technique exhibit the expected dynamics of auroral electrojets and polar caps in two hemispheres. Hall current intensities in polar caps and auroral electrojets, calculated from the equivalent current function, change fairly synchronously in the N and S hemispheres throughout the magnetic storm. Both (westward and eastward) electrojets of the N hemisphere are markedly more intense than respective electrojets of the S hemisphere, and the Hall current in the north polar cap is almost twice as intense as that in the south one. This interhemispheric asymmetry is likely to be due to seasonal conductance variations, which is implicitly contained in the current function. From FAC distributions we determine auroral oval boundaries and calculate magnetic fluxes through the polar caps in the N and S hemispheres. These magnetic fluxes coincide with an accuracy of about 5 % and change almost synchronously during the magnetic storm. In the N hemisphere, the magnetic flux in the dawn polar cap is more intense that that in the dusk one, and vice versa in the S hemisphere. These asymmetries (dawn–dusk and interhemispheric) in the polar caps are consistent with the theory of reconnection for IMF By>0 and with satellite images of auroral ovals; both of these asymmetries decrease during the substorm expansion phase.
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Xue, Jiaqing, Bingchao Wang, Yongkui Yu, Jianping Li, Cheng Sun, and Jiangyu Mao. "Multidecadal variation of northern hemisphere summer monsoon forced by the SST inter-hemispheric dipole." Environmental Research Letters 17, no. 4 (March 21, 2022): 044033. http://dx.doi.org/10.1088/1748-9326/ac5a65.
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Abstract The sea surface temperature inter-hemispheric dipole (SSTID) is an important variability mode of global SST anomalies, characterized by an anti-phase variation of SST between the two hemispheres. In this study, the decadal variation of the northern hemisphere summer monsoon (NHSM) is found to be strongly regulated by the SSTID, with positive (negative) phases of the SSTID corresponding to the strengthening (weakening) of NHSM. Both observation and SST-forced atmospheric model simulations suggest that the SSTID related thermal forcing modulates the NHSM by causing planetary-scale atmospheric circulation adjustments. Positive SSTID events lead to coherent increase (decrease) of surface air temperature over the entire northern (southern) hemisphere, increasing the inter-hemispheric thermal contrast (ITC). As sea level pressure changes are just opposite to air temperature, the increase of ITC enhances the inter-hemispheric pressure gradient (southern hemisphere minus northern hemisphere), leading to the strengthening of summer monsoonal circulation and the increase of monsoon rainfall in the northern hemisphere.
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Shibahara, Naoki, and Brennis Lucero-Wagoner. "Access to Concrete Word Meanings in the Cerebral Hemispheres: Facilitation and Inhibition Effects." Perceptual and Motor Skills 96, no. 1 (February 2003): 166–72. http://dx.doi.org/10.2466/pms.2003.96.1.166.
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In 2002 Shibahara and Lucero-Wagoner, using a priming paradigm, reported a larger facilitation for concrete noun pairs in the right than left hemisphere when the stimulus onset asynchrony was 250 msec. Their related prime-target pairs were similar not only in meaning but also perceptual attributes, such as shape. They had reported such perceptual information to be available only in the right hemisphere early in target processing. Thus, we predicted that, when the stimulus onset asynchrony is long, there would be no effect of perceptual information on target processing in the right hemisphere, resulting in no hemispheric differences in the amount of facilitation. We also predicted that target processing would be inhibited by prior presentation of unrelated primes only in the left hemisphere because inhibition seems to be produced by the attention system in the left hemisphere. The present experiment was designed to test these predictions, using the stimulus onset asynchrony of 550 msec. and the same prime-target pairs. Analysis showed no hemispheric differences in the amount of facilitation, and inhibition effects for unrelated pairs were produced in both hemispheres. It is suggested that the inhibition effects in each hemisphere might be produced by different mechanisms.
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Aparicio, A. J. P., V. M. S. Carrasco, M. C. Gallego, and J. M. Vaquero. "Hemispheric Sunspot Number from the Madrid Astronomical Observatory for the Period 1935–1986." Astrophysical Journal 931, no. 1 (May 1, 2022): 52. http://dx.doi.org/10.3847/1538-4357/ac5dc6.
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Abstract Long-term studies on hemispheric asymmetry can help to understand better the solar dynamo. We present the hemispheric sunspot number calculated from daily sunspot observations made at the Madrid Astronomical Observatory for the period 1935–1986 (corresponding approximately to Solar Cycles 17–21). From this data set, we also analyzed the asymmetry index and hemispheric phase shifts. We conclude that the northern hemisphere was predominant in Solar Cycles 17–20, whereas the southern hemisphere was predominant in Solar cycle 21. The strongest asymmetries are found in Solar Cycles 20 (with a relative difference between both hemispheres of 44%) and 19 (39%). A normalization of the Madrid hemispheric sunspot number was also made with respect to the sunspot number (Version 2). Our results agree with previous studies on hemispheric asymmetry around the mid-20th century and their secular trends.
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Voigt, Aiko, Bjorn Stevens, Jürgen Bader, and Thorsten Mauritsen. "Compensation of Hemispheric Albedo Asymmetries by Shifts of the ITCZ and Tropical Clouds." Journal of Climate 27, no. 3 (January 24, 2014): 1029–45. http://dx.doi.org/10.1175/jcli-d-13-00205.1.
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Abstract Despite a substantial hemispheric asymmetry in clear-sky albedo, observations of Earth’s radiation budget reveal that the two hemispheres have the same all-sky albedo. Here, aquaplanet simulations with the atmosphere general circulation model ECHAM6 coupled to a slab ocean are performed to study to what extent and by which mechanisms clouds compensate hemispheric asymmetries in clear-sky albedo. Clouds adapt to compensate the imposed asymmetries because the intertropical convergence zone (ITCZ) shifts into the dark surface hemisphere. The strength of this tropical compensation mechanism is linked to the magnitude of the ITCZ shift. In some cases the ITCZ shift is so strong as to overcompensate the hemispheric asymmetry in clear-sky albedo, yielding a range of climates for which the hemisphere with lower clear-sky albedo has a higher all-sky albedo. The ITCZ shift is sensitive to the convection scheme and the depth of the slab ocean. Cloud–radiative feedbacks explain part of the sensitivity to the convection scheme as they amplify the ITCZ shift in the Tiedtke (TTT) scheme but have a neutral effect in the Nordeng (TNT) scheme. A shallower slab ocean depth, and thereby reduced thermal inertia of the underlying surface and increased seasonal cycle, stabilizes the ITCZ against annual-mean shifts. The results lend support to the idea that the climate system adjusts so as to minimize hemispheric albedo asymmetries, although there is no indication that the hemispheres must have exactly the same albedo.
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Van Kaam, Ruud C., Michel J. A. M. van Putten, Sarah E. Vermeer, and Jeannette Hofmeijer. "Contralesional Brain Activity in Acute Ischemic Stroke." Cerebrovascular Diseases 45, no. 1-2 (2018): 85–92. http://dx.doi.org/10.1159/000486535.
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Background: The noninjured, contralateral hemisphere is increasingly acknowledged in the process of recovery from acute ischemic stroke. We estimated the value of conventional electroencephalography (EEG) recordings for identifying contralateral hemisphere involvement in relation to functional recovery. Methods: We analyzed 2-min epochs from 21 electrode EEG registrations of 18 patients with acute hemispheric ischemic stroke and compared with 18 age-matched controls. Outcome was dichotomized as good (modified Rankin Scale [mRS] 0–2) or poor (mRS 3–5 or death) at 3 months. Effects of the infarct on the ipsi-and contralateral hemispheres were analyzed by the delta/alpha ratio (DAR) and 2 measures of functional connectivity (magnitude squared coherence [MSC] and weighted phase lag index [WPLI]). Results: DAR was higher in patients than in controls, both in the ipsilateral and in the contralateral hemisphere (median 4.5 ± 6.7 ipsilateral and 2.4 ± 2.0 contralateral vs. 0.5 ± 0.5 in the control group, p < 0.001), indicating robust EEG changes in both lesioned and non-lesioned hemisphere. MSC and WPLI in the alpha and beta frequency bands were lower in patients than in controls in both hemispheres, indicating clear disturbances of functional connectivity (p < 0.05). In the poor outcome group, contralateral MSC and WPLI were lower than in the good outcome group, although these differences did not reach statistical significance. Conclusions: Short conventional EEG measurements show robust changes of brain activity and functional connectivity in both ipsilateral and contralateral hemispheres of patients with acute ischemic stroke. Changes of remote functional connectivity tend to interact with functional recovery. Future studies should estimate predictive values for individual patients and interactions with plasticity enhancing treatments.
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Veronig, Astrid M., Shantanu Jain, Tatiana Podladchikova, Werner Pötzi, and Frederic Clette. "Hemispheric sunspot numbers 1874–2020." Astronomy & Astrophysics 652 (August 2021): A56. http://dx.doi.org/10.1051/0004-6361/202141195.
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Context. Previous studies show significant north–south asymmetries for various features and indicators of solar activity. These findings suggest some decoupling between the two hemispheres over the solar cycle evolution, which is in agreement with dynamo theories. For the most important solar activity index, the sunspot numbers, so far only limited data are available for the two hemispheres independently. Aims. The aim of this study is to create a continuous series of daily and monthly hemispheric sunspot numbers (HSNs) from 1874 to 2020, which will be continuously expanded in the future with the HSNs provided by SILSO. Methods. Based on the available daily measurements of hemispheric sunspot areas from 1874 to 2016 from Greenwich Royal Observatory and National Oceanic and Atmospheric Administration, we derive the relative fractions of the northern and southern activity. These fractions are applied to the international sunspot number (ISN) to derive the HSNs. This method and obtained data are validated against published HSNs for the period 1945–2004 and those provided by SILSO for 1992 to 2016. Results. We provide a continuous data series and catalogue of daily, monthly mean, and 13-month smoothed monthly mean HSNs for the time range 1874–2020 –fully covering solar cycles 12 to 24– that are consistent with the newly calibrated ISN (Clette et al., 2014). Validation of the reconstructed HSNs against the direct data available since 1945 reveals a high level of consistency, with Pearson correlation coefficients of r = 0.94 (0.97) for the daily (monthly mean) data. The cumulative hemispheric asymmetries for cycles 12–24 give a mean value of 16%, with no obvious pattern in north–south predominance over the cycle evolution. The strongest asymmetry occurs for cycle no. 19, in which the northern hemisphere shows a cumulated predominance of 42%. The phase shift between the peaks of solar activity in the two hemispheres may be up to 28 months, with a mean absolute value over cycles 12–24 of 16.8 months. The phase shifts reveal an overall asymmetry of the northern hemisphere reaching its cycle maximum earlier (in 10 out of 13 cases), with a mean signed phase shift of −7.6 months. Relating the ISN and HSN peak growth rates during the cycle rise phase with the cycle amplitude reveals higher correlations when considering the two hemispheres individually, with r ≈ 0.9. Conclusions. Our findings provide further evidence that to some degree the solar cycle evolves independently in the two hemispheres, and demonstrate that empirical solar cycle prediction methods can be improved by investigating the solar cycle dynamics in terms of the HSN evolution.
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Lin 林, Jiaqi 家琪, Feng 锋. Wang 王, Linhua 林华 Deng 邓, Hui 辉. Deng 邓, Ying 盈. Mei 梅, and Xiaojuan 小娟 Zhang 张. "Evolutionary Relationship between Sunspot Groups and Soft X-Ray Flares over Solar Cycles 21–25." Astrophysical Journal 958, no. 1 (November 1, 2023): 1. http://dx.doi.org/10.3847/1538-4357/ad0469.
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Abstract Studying the interaction between solar flares and sunspot groups (SGs) is crucial for understanding and predicting solar activity. We examined the distribution, correlation, and flaring rates in the northern and southern hemispheres to reveal the relationship between different classes of soft X-ray (SXR) flares and different magnetic classifications of SGs. We discovered a significant north–south asymmetry in SXR flares and SG distribution over Solar Cycles (SC) 21–25. In the rising phase of SC24, the northern hemisphere’s activity is significantly excessive. In the declining phase of SC24, the southern hemisphere’s activity becomes significantly excessive. The total numbers of various SXR flares and SGs vary between the northern and southern hemispheres over the solar cycle. B-class flares are negatively correlated with all SGs at maximum but positively correlated at minimum. C-class flares correlate best with α and β SGs. M-class flares correlate best with β γ δ and β SGs. X-class flares correlate highest with β γ δ SGs. The flaring rate of each flare class is lowest for α SGs and highest for β γ δ SGs. The flaring rates are higher in the southern hemisphere than in the northern hemisphere. Our results demonstrate that solar flares originate from different sources of solar active regions; the high-energy flares tend to be caused by more complex magnetic fields.
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Hosokawa, K., E. E. Woodfield, M. Lester, S. E. Milan, N. Sato, A. S. Yukimatu, and T. Iyemori. "Interhemispheric comparison of spectral width boundary as observed by SuperDARN radars." Annales Geophysicae 21, no. 7 (July 31, 2003): 1553–65. http://dx.doi.org/10.5194/angeo-21-1553-2003.
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Abstract. Previous studies have shown that dayside equatorward edge of coherent HF radar backscatter having broad Doppler spectral width is coincident with the equatorward edge of the cusp particle precipitation. This enables the boundary between broad and narrow spectral width backscatters (spectral width boundary) in the dayside magnetic local time sector to be used as a proxy for the open/closed field line boundary. The present case study employs magnetically conjugate SuperDARN coherent HF radars to make an inter-hemispheric comparison of the location and variation of the spectral width boundaries. Agreement between the magnetic latitudes of the boundaries in both hemispheres is remarkable. Correlation coefficients between the latitudes of the boundaries are larger than 0.70. Temporal variation of the spectral width boundary follows the same equatorward trend in both hemispheres. This is consistent with the accumulation of open flux in the polar cap by dayside low-latitude magnetopause reconnection, expected when IMF Bz is negative. Boundaries in both hemispheres also exhibit short-lived poleward motions superposed on the general equator-ward trend, which follows the onset of substorm expansion phase and a temporary northward excursion of IMF Bz during substorm recovery phase. There is an interhemispheric difference in response time to the substorm occurrence between two hemispheres. The spectral width boundary in the Southern Hemisphere starts to move poleward 10 min earlier than that in the Northern Hemisphere. We discuss this difference in terms of interhemispheric asymmetry of the substorm breakup region in the longitudinal direction associated with the effect of IMF By.Key words. Ionosphere (ionosphere-magnetosphere interactions; plasma convection) – Magnetospheric physics (magnetopause, cusp, boundary layers)
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Wijaya, Evan. "Game Utilization as a Media to Train the Balance of Left and Right Brain." SISFORMA 4, no. 1 (October 19, 2017): 12. http://dx.doi.org/10.24167/sisforma.v4i1.1042.
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Human have two brain hemispheres, left hemisphere and right hemisphere. Left hemisphere is used for processing language, words, numbers, equations, etc. Right hemisphere is used for processing creativity, imagination, music, color, etc. Every human should have balance between left and right hemisphere. One method that could be used for balancing brain hemispheres is to use left and right hands for using tools, writing, or typing. “Typing Rhythm” is a game for PC platform, the purpose of this game is for brain balancing exercise by typing lyric of a song while the song is played.
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Weisbrod, Matthias, Sabine Maier, Sabine Harig, Ulrike Himmelsbach, and Manfred Spitzer. "Lateralised semantic and indirect semantic priming effects in people with schizophrenia." British Journal of Psychiatry 172, no. 2 (February 1998): 142–46. http://dx.doi.org/10.1192/bjp.172.2.142.
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BackgroundIn schizophrenia, disturbances in the development of physiological hemisphere asymmetry are assumed to play a pathogenetic role. The most striking difference between hemispheres is in language processing. The left hemisphere is superior in the use of syntactic or semantic information, whereas the right hemisphere uses contextual information more effectively.MethodUsing psycholinguistic experimental techniques, semantic associations were examined in 38 control subjects, 24 non-thought-disordered and 16 thought-disordered people with schizophrenia, for both hemispheres separately.ResultsDirect semantic priming did not differ between the hemispheres in any of the groups. Only thought-disordered people showed significant indirect semantic priming in the left hemisphere.ConclusionsThe results support: (a) a prominent role of the right hemisphere for remote associations; (b) enhanced spreading of semantic associations in thought-disordered subjects; and (c) disorganisation of the functional asymmetry of semantic processing in thought-disordered subjects.
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Hartikainen, Kaisa M. "Emotion-Attention Interaction in the Right Hemisphere." Brain Sciences 11, no. 8 (July 29, 2021): 1006. http://dx.doi.org/10.3390/brainsci11081006.
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Hemispheric asymmetries in affective and cognitive functions have been extensively studied. While both cerebral hemispheres contribute to most affective and cognitive processes, neuroscientific literature and neuropsychological evidence support an overall right hemispheric dominance for emotion, attention and arousal. Emotional stimuli, especially those with survival value such as threat, tend to be prioritized in attentional resource competition. Arousing unpleasant emotional stimuli have prioritized access, especially to right-lateralized attention networks. Interference of task performance may be observed when limited resources are exhausted by task- and emotion-related processing. Tasks that rely on right hemisphere-dependent processing, like attending to the left visual hemifield or global-level visual features, are especially vulnerable to interference due to attention capture by unpleasant emotional stimuli. The aim of this review is to present literature regarding the special role of the right hemisphere in affective and attentional brain processes and their interaction. Furthermore, clinical and technological implications of this interaction will be presented. Initially, the effects of focal right hemisphere lesion or atrophy on emotional functions will be introduced. Neurological right hemisphere syndromes including aprosodia, anosognosia and neglect, which further point to the predominance of the intact right hemisphere in emotion, attention and arousal will be presented. Then there will be a brief review of electrophysiological evidence, as well as evidence from patients with neglect that support attention capture by emotional stimuli in the right hemisphere. Subsequently, experimental work on the interaction of emotion, attention and cognition in the right hemispheres of healthy subjects will be presented. Finally, clinical implications for better understanding and assessment of alterations in emotion–attention interaction due to brain disorder or treatment, such as neuromodulation, that impact affective brain functions will be discussed. It will be suggested that measuring right hemispheric emotion–attention interactions may provide basis for novel biomarkers of brain health. Such biomarkers allow for improved diagnostics in brain damage and disorders and optimized treatments. To conclude, future technological applications will be outlined regarding brain physiology-based measures that reflect engagement of the right hemisphere in affective and attentional processes.
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Dixon, Tanner C., Christina M. Merrick, Joni D. Wallis, Richard B. Ivry, and Jose M. Carmena. "Hybrid dedicated and distributed coding in PMd/M1 provides separation and interaction of bilateral arm signals." PLOS Computational Biology 17, no. 11 (November 22, 2021): e1009615. http://dx.doi.org/10.1371/journal.pcbi.1009615.
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Pronounced activity is observed in both hemispheres of the motor cortex during preparation and execution of unimanual movements. The organizational principles of bi-hemispheric signals and the functions they serve throughout motor planning remain unclear. Using an instructed-delay reaching task in monkeys, we identified two components in population responses spanning PMd and M1. A “dedicated” component, which segregated activity at the level of individual units, emerged in PMd during preparation. It was most prominent following movement when M1 became strongly engaged, and principally involved the contralateral hemisphere. In contrast to recent reports, these dedicated signals solely accounted for divergence of arm-specific neural subspaces. The other “distributed” component mixed signals for each arm within units, and the subspace containing it did not discriminate between arms at any stage. The statistics of the population response suggest two functional aspects of the cortical network: one that spans both hemispheres for supporting preparatory and ongoing processes, and another that is predominantly housed in the contralateral hemisphere and specifies unilateral output.
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Matus-Leibovitch, N., D. R. Nussenzveig, M. C. Gershengorn, and Y. Oron. "The hemispheric functional expression of the thyrotropin-releasing-hormone receptor is not determined by the receptors' physical distribution." Biochemical Journal 303, no. 1 (October 1, 1994): 129–34. http://dx.doi.org/10.1042/bj3030129.
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The thyrotropin-releasing-hormone receptor (TRH-R) is a member of a family of the G-protein-coupled receptors that share structural similarities and exert their physiological action via the inositol lipid signal-transduction pathway. The TRH-R when expressed in Xenopus oocytes exhibits marked preference of the response (increased chloride conductance) for the animal hemisphere. Whereas the rat TRH-R functional distribution was strongly asymmetric (animal/vegetal ratio = 9.5), the mouse TRH-R exhibited a significantly lower ratio (3.9). Truncation of the last 59 amino acids of the C-terminal region of the mouse TRH-R did not lead to any changes in the functional hemispheric distribution. Despite the polarization of response, receptor number was similar on both hemispheres. Moreover, the apparent half-life of the functional expression of the TRH-R was approx. 4 h on both hemispheres when the expression was inhibited by a specific antisense oligonucleotide. Inhibition of total protein synthesis with cycloheximide affected hemispheric responses mediated by each of the three TRH-Rs tested in a qualitatively different way. These results suggest that an additional, rapidly degraded, protein modulates the functional hemispheric expression of the TRH-Rs.
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Piechnik, Stefan K., Marek Czosnyka, Neil G. Harris, Pawan S. Minhas, and John D. Pickard. "A Model of the Cerebral and Cerebrospinal Fluid Circulations to Examine Asymmetry in Cerebrovascular Reactivity." Journal of Cerebral Blood Flow & Metabolism 21, no. 2 (February 2001): 182–92. http://dx.doi.org/10.1097/00004647-200102000-00010.
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The authors examined the steal phenomenon using a new mathematical model of cerebral blood flow and the cerebrospinal fluid circulation. In this model, the two hemispheres are connected through the circle of Willis by an anterior communicating artery (ACoA) of varying size. The right hemisphere has no cerebrovascular reactivity and the left is normally reactive. The authors studied the asymmetry of hemispheric blood flow in response to simulated changes in arterial blood pressure and carbon dioxide concentration. The hemispheric blood flow was dependent on the local regulatory capacity but not on the size of the ACoA. Flow through the ACoA and carotid artery was strongly dependent on the size of the communicating artery. A global interhemispheric “steal effect” was demonstrated to be unlikely to occur in subjects with nonstenosed carotid arteries. Vasoreactive effects on intracranial pressure had a major influence on the circulation in both hemispheres, provoking additional changes in blood flow on the nonregulating side. A method for the quantification of the crosscirculatory capacity has been proposed.
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Engelhardt, Melina, and Thomas Picht. "1 Hz Repetitive Transcranial Magnetic Stimulation of the Primary Motor Cortex: Impact on Excitability and Task Performance in Healthy Subjects." Journal of Neurological Surgery Part A: Central European Neurosurgery 81, no. 02 (February 11, 2020): 147–54. http://dx.doi.org/10.1055/s-0040-1701624.
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Abstract Objective Neuronavigated repetitive transcranial stimulation (rTMS) at a frequency of 1 Hz was shown to reduce excitability in underlying brain areas while increasing excitability in the opposite hemisphere. In stroke patients, this principle is used to normalize activity between the lesioned and healthy hemispheres and to facilitate rehabilitation. However, standardization is lacking in applied protocols, and there is a poor understanding of the underlying physiologic mechanisms. Furthermore, the influence of hemispheric dominance on the intervention has not been studied before. A systematic evaluation of the effects in healthy subjects would deepen the understanding of these mechanisms and offer insights into ways to improve the intervention. Methods Twenty healthy subjects underwent five 15-minute sessions of neuronavigated rTMS or sham stimulation over their dominant or nondominant motor cortex. Dominance was assessed with the Edinburgh Handedness Inventory. Changes in both hemispheres were measured using behavioral parameters (finger tapping, grip force, and finger dexterity) and TMS measures (resting motor threshold, recruitment curve, motor area, and cortical silent period). Results All subjects tolerated the stimulation well. A pronounced improvement was noted in finger tapping scores over the nonstimulated hemisphere as well as a nonsignificant reduction of the cortical silent period in the stimulated hemisphere, indicating a differential effect of the rTMS on both hemispheres. Grip force remained at the baseline level in the rTMS group while decreasing in the sham group, suggesting the rTMS counterbalanced the effects of fatigue. Lastly, dominance did not influence any of the observed effects. Conclusions This study shows the capability of the applied low-frequency rTMS protocol to modify excitability of underlying brain areas as well as the contralateral hemisphere. It also highlights the need for a better understanding of underlying mechanisms and the identification of predictors for responsiveness to rTMS. However, results should be interpreted with caution because of the small sample size.
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Mendillo, M., and C. Narvaez. "Ionospheric storms at geophysically-equivalent sites – Part 2: Local time storm patterns for sub-auroral ionospheres." Annales Geophysicae 28, no. 7 (July 15, 2010): 1449–62. http://dx.doi.org/10.5194/angeo-28-1449-2010.
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Abstract. The response of the mid-latitude ionosphere to geomagnetic storms depends upon several pre-storm conditions, the dominant ones being season and local time of the storm commencement (SC). The difference between a site's geographic and geomagnetic latitudes is also of major importance since it governs the blend of processes linked to solar production and magnetospheric input, respectively. Case studies of specific storms using ionospheric data from both hemispheres are inherently dominated by seasonal effects and the various local times versus longitude of the SCs. To explore inter-hemispheric consistency of ionospheric storms, we identify "geophysically-equivalent-sites" as locations where the geographic and geomagnetic latitudes have the same relationship to each other in both hemispheres. At the longitudes of the dipole tilt, the differences between geographic and geomagnetic latitudes are at their extremes, and thus these are optimal locations to see if pre-conditioning and/or storm-time input are the same or differ between the hemispheres. In this study, we use ionosonde values of the F2-layer maximum electron density (NmF2) to study geophysical equivalency at Wallops Island (VA) and Hobart (Tasmania), using statistical summaries of 206 events during solar cycle #20. We form average patterns of ΔNmF2 (%) versus local time over 7-day storm periods that are constructed in ways that enhance the portrayal of the average characteristic features of the positive and negative phases of ionospheric storms. The results show a consistency between four local time characteristic patterns of storm-induced perturbations, and thus for the average magnitudes and time scales of the processes that cause them in each hemisphere. Subtle differences linked to small departures from pure geophysical equivalency point to a possible presence of hemispheric asymmetries governed by the non-mirror-image of geomagnetic morphology in each hemisphere.
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Djukic-Macut, Natasa, Slobodan Malobabic, Natalija Stefanovic, Predrag Mandic, Tatjana Filipovic, Aleksandar Malikovic, and Milena Saranovic. "Asymmetries in numerical density of pyramidal neurons in the fifth layer of the human posterior parietal cortex." Vojnosanitetski pregled 69, no. 8 (2012): 681–85. http://dx.doi.org/10.2298/vsp101126016d.
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Background/Aim. Both superior parietal lobule (SPL) of dorsolateral hemispheric surface and precuneus (PEC) of medial surface are the parts of posterior parietal cortex. The aim of this study was to determine the numerical density (NV) of pyramidal neurons in the layer V of SPL and PEC and their potential differences. Methods. From 20 (40 hemispheres) formaline fixed human brains (both sexes; 27- 65 years) tissue blocks from SPL and PEC from the left and right hemisphere were used. According to their size the brains were divided into two groups, the group I with the larger left (15 brains) and the group II with the larger right hemisphere (5 brains). Serial Nissl sections (5 ?m) of the left and right SPL and PEC were used for stereological estimation of NV of the layer V pyramidal neurons. Results. NV of pyramidal neurons in the layer V in the left SPL of brains with larger left hemispheres was significantly higher than in the left SPL of brains with larger right hemisphere. Comparing sides in brains with larger left hemisphere, the left SPL had higher NV than the right one, and then the left PEC, and the right SPL had significantly higher NV than the right PEC. Comparing sides in brains with the larger right hemisphere, the left SPL had significantly higher NV than left PEC, but the right SPL had significantly higher NV than left SPL and the right PEC. Conclusion. Generally, there is an inverse relationship of NV between the medial and lateral areas of the human posterior parietal cortex. The obtained values were different between the brains with larger left and right hemispheres, as well as between the SPL and PEC. In all the comparisons the left SPL had the highest values of NV of pyramidal neurons in the layer V (4771.80 mm-3), except in brains with the larger right hemisphere.
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Metcalfe, Janet, Margaret Funnell, and Michael S. Gazzaniga. "Right-Hemisphere Memory Superiority: Studies of a Split-Brain Patient." Psychological Science 6, no. 3 (May 1995): 157–64. http://dx.doi.org/10.1111/j.1467-9280.1995.tb00325.x.
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Six experiments explored hemispheric memory differences in a patient who had undergone complete corpus callosum resection The right hemisphere was better able than the left to reject new events similar to originally presented materials of several types, including abstract visual forms, faces, and categorized lists of words Although the left hemisphere is capable of mental manipulation, imagination, semantic priming, and complex language production, these functions are apparently linked to memory confusions—confusions less apparent in the more literal right hemisphere Differences between the left and right hemispheres in memory for new schematically consistent or categorically related events may provide a source of information allowing people to distinguish between what they actually witnessed and what they only inferred
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Sakreida, Katrin, Johanna Blume-Schnitzler, Grit Frankemölle, Vanessa Drews, Stefan Heim, Klaus Willmes, Hans Clusmann, and Georg Neuloh. "Hemispheric Dominance for Language and Side Effects in Mapping the Inferior Frontal Junction Area with Transcranial Magnetic Stimulation." Journal of Neurological Surgery Part A: Central European Neurosurgery 81, no. 02 (February 11, 2020): 130–37. http://dx.doi.org/10.1055/s-0040-1701236.
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Abstract Background and Study Aims Language mapping by navigated transcranial magnetic stimulation (TMS) is commonly applied over the left language-dominant hemisphere to indicate the language-related cortex. Detailed language mapping of Broca's region including stimulation targets in the immediate vicinity to the premotor cortex may raise concern about confounding unspecific motor effects. We performed interhemispheric comparisons to delineate such possible unspecific effects from true TMS-induced language inhibition. Material and Methods Fifteen healthy German speakers named object pictures during navigated TMS over a left- and right-hemispheric target array covering the left inferior frontal junction area. Six mapping repetitions were conducted per hemisphere. Order of stimulation side was randomized between participants. Self-rating of discomfort was assessed after each stimulation; language errors and motor side effects were evaluated offline. Results Naming errors were observed significantly more frequently during left- than right-hemispheric stimulation. The same pattern was found for the most frequent error category of performance errors. Hierarchical cluster analyses of normalized ratings of error severity revealed a clear focus of TMS susceptibility for language inhibition in object naming at the dorsoposterior target sites only in the left hemisphere. We found no statistical difference in discomfort ratings between both hemispheres and also no interhemispheric difference in motor side effects, but we observed significantly stronger muscle contractions of the eyes as compared with the mouth. Conclusion Our results of (1) unspecific pre-/motor effects similarly induced in both hemispheres, and (2) a specific focus of TMS susceptibility in the language-dominant hemisphere render any substantial contribution of nonlanguage-specific effects in TMS language mapping of the inferior frontal junction area highly unlikely.
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Jang, Junseok, Sungyeong Ryu, Dong Ah Lee, and Kang Min Park. "Are there network differences between the ipsilateral and contralateral hemispheres of pain in patients with episodic migraine without aura?" Annals of Clinical Neurophysiology 25, no. 2 (October 31, 2023): 93–102. http://dx.doi.org/10.14253/acn.2023.25.2.93.
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Background: We aimed to identif y any differences in the structural covariance network based on structural volume and those in the functional network based on cerebral blood flow between the ipsilateral and contralateral hemispheres of pain in patients with episodic migraine without aura.Methods: We prospectively enrolled 27 patients with migraine without aura, all of whom had unilateral migraine pain. We defined the ipsilateral hemisphere as the side of migraine pain. We measured structural volumes on three-dimensional T1-weighted images and cerebral blood flow using arterial spin labeling magnetic resonance imaging. We then analyzed the structural covariance network based on structural volume and the functional network based on cerebral blood flow using graph theory. Results: There were no significant differences in structural volume or cerebral blood flow between the ipsilateral and contralateral hemispheres. However, there were significant differences between the hemispheres in the structural covariance network and the functional network. In the structural covariance network, the betweenness centrality of the thalamus was lower in the ipsilateral hemisphere than in the contralateral hemisphere. In the functional network, the betweenness centrality of the anterior cingulate and paracingulate gyrus was lower in the ipsilateral hemisphere than in the contralateral hemisphere, while that of the opercular part of the inferior frontal gyrus was higher in the former hemisphere.Conclusions: The present findings indicate that there are significant differences in the structural covariance network and the functional network between the ipsilateral and contralateral hemispheres of pain in patients with episodic migraine without aura.
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Сяська, Інна. "PSYCHOLOGICAL AND PEDAGOGICAL APPROACHES TO THE LEARNING ACTIVITIES OF PUPILS WITH DIFFERENT LATERALISATION OF THE CEREBRAL HEMISPHERES." Педагогічна наука і освіта ХХІ століття, no. 2 (May 1, 2024): 49–60. http://dx.doi.org/10.35619/pse.vi2.24.
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The study of the functional asymmetry of the cerebral hemispheres is an important problem of modern science. Teaching that takes into account functional asymmetry can be more effective and contribute to the development of the child’s full potential, including students with special educational needs. It has been proven that school teaching methods are usually focused on the development of the left hemisphere. This is due to the fact that language is the main means of learning at school. In the process of learning, the functional asymmetry increases: the left hemisphere specialises in symbolic operations, and the right hemisphere in figurative ones. However, teaching left- and right-brained students should not be the same. The predominance of left or right brain activity determines the type of thinking a person has, their character, temperament, memory, hand dominance and other psychophysiological features that must be taken into account for effective teaching. To study the peculiarities of the distribution of functional asymmetry of the brain, we selected 14-15 aged students, in which the process of lateralisation is considered to be completed. The results of the study of the coefficient of functional asymmetry of the brain and the type of temperament of 9th grade students of the experimental and control groups are presented. The obtained results correspond to the average world indicators. General recommendations for improving the academic achievements of adolescents with different lateralisation of the hemispheres, taking into account their individual characteristics, in particular the dominant type of temperament. The psychological and pedagogical approaches to the effective implementation of the educational process for right- and left-hemispheric students and ambidextrous students are proposed, which contain methodological recommendations for the selection of forms, methods and means of teaching students, taking into account their functional asymmetry of the hemispheres.
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Virtanen, I. O. I., I. I. Virtanen, A. A. Pevtsov, and K. Mursula. "Reconstructing solar magnetic fields from historical observations." Astronomy & Astrophysics 616 (August 2018): A134. http://dx.doi.org/10.1051/0004-6361/201732323.
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Aims. Sunspot activity is often hemispherically asymmetric, and during the Maunder minimum, activity was almost completely limited to one hemisphere. In this work, we use surface flux simulation to study how magnetic activity limited only to the southern hemisphere affects the long-term evolution of the photospheric magnetic field in both hemispheres. The key question is whether sunspot activity in one hemisphere is enough to reverse the polarity of polar fields in both hemispheres. Methods. We simulated the evolution of the photospheric magnetic field from 1978 to 2016 using the observed active regions of the southern hemisphere as input. We studied the flow of magnetic flux across the equator and its subsequent motion towards the northern pole. We also tested how the simulated magnetic field is changed when the activity of the southern hemisphere is reduced. Results. We find that activity in the southern hemisphere is enough to reverse the polarity of polar fields in both hemispheres by the cross-equatorial transport of magnetic flux. About 1% of the flux emerging in the southern hemisphere is transported across the equator, but only 0.1%–0.2% reaches high latitudes to reverse and regenerate a weak polar field in the northern hemisphere. The polarity reversals in the northern hemisphere are delayed compared to the southern hemisphere, leading to a quadrupole Sun lasting for several years.
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Kuroda, Satoshi, Shusuke Yamamoto, Takeshi Funaki, Miki Fujimura, Hiroharu Kataoka, Tomohito Hishikawa, Jun Takahashi, et al. "Five-Year Stroke Risk and Its Predictors in Asymptomatic Moyamoya Disease: Asymptomatic Moyamoya Registry (AMORE)." Stroke 54, no. 6 (June 2023): 1494–504. http://dx.doi.org/10.1161/strokeaha.122.041932.
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Background: Long-term outcomes are unknown in patients with asymptomatic moyamoya disease. In this report, we aimed to clarify their 5-year risk of stroke and its predictors. Methods: We are conducting a multicenter, prospective cohort study (Asymptomatic Moyamoya Registry) in Japan. Participants were eligible if they were 20 to 70 years, had bilateral or unilateral moyamoya disease, experienced no episodes suggestive of TIA and stroke; and were functionally independent (modified Rankin Scale score 0–1). Demographic and radiological information was collected at enrollment. In this study, they are still followed up for 10 years. In this interim analysis, we defined the primary end point as a stroke occurring during a 5-year follow-up period. Independent predictors for stroke were also determined, using a stratification analysis method. Results: Between 2012 and 2015, we enrolled 109 patients, of whom 103 patients with 182 involved hemispheres completed the 5-year follow-up. According to the findings on DSA and MRA, 143 hemispheres were judged as moyamoya disease and 39 hemispheres as questionable manifestations (isolated middle cerebral artery stenosis). The patients with questionable hemispheres were significantly older, more often male, and more frequently had hypertension than those with moyamoya hemisphere. Moyamoya hemispheres developed 7 strokes, including 6 hemorrhagic and 1 ischemic stroke, during the first 5 years. The annual risk of stroke was 1.4% per person, 0.8% per hemisphere, and 1.0% per moyamoya hemisphere. Independent predictor for stroke was Grade-2 choroidal anastomosis (hazard ratio, 5.05 [95% CI, 1.24–20.6]; P =0.023). Furthermore, microbleeds (hazard ratio, 4.89 [95% CI, 1.13-21.3]; P =0.0342) and Grade-2 choroidal anastomosis (hazard ratio, 7.05 [95% CI, 1.62–30.7]; P =0.0093) significantly predicted hemorrhagic stroke. No questionable hemispheres developed any stroke. Conclusions: The hemispheres with asymptomatic moyamoya disease may carry a 1.0% annual risk of stroke during the first 5 years, the majority of which are hemorrhagic stroke. Grade-2 choroidal anastomosis may predict stroke, and the microbleeds and Grade-2 choroidal anastomosis may carry the risk for hemorrhagic stroke. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: UMIN000006640.
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Nemoto, Edwin M., Howard Yonas, Hiroto Kuwabara, Ronda R. Pindzola, Donald Sashin, Carolyn C. Meltzer, Julie C. Price, Yuefang Chang, and David W. Johnson. "Identification of Hemodynamic Compromise by Cerebrovascular Reserve and Oxygen Extraction Fraction in Occlusive Vascular Disease." Journal of Cerebral Blood Flow & Metabolism 24, no. 10 (October 2004): 1081–89. http://dx.doi.org/10.1097/01.wcb.0000125887.48838.37.
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Cerebrovascular reserve (CVR) and oxygen extraction fraction (OEF) are used to identify hemodynamic compromise in symptomatic patients with carotid occlusive vascular disease, but evidence suggests that they are not equivalent. The authors studied the relationship between CVR and OEF to evaluate their equivalence and stages of hemodynamic compromise. Symptomatic patients (N = 12) with carotid occlusion were studied by stable xenon–computed tomography CBF after intravenous acetazolamide administration for CVR, followed within 24 hours by positron emission tomography (PET) for OEF. Middle cerebral artery territories were analyzed by hemisphere and level. Hemispheric subcortical white matter infarctions were graded with magnetic resonance imaging. Both hemispheric and level analysis of CVR and OEF showed a significant ( P = 0.001), negative linear relationship [CVR (%) = −1.5 (OEF) + 83.4, ( r = −0.57, P = 0.001, n = 24]. However, 37.5% of the hemispheres showed compromised CVR but normal OEF and were associated ( P = 0.019) with subcortical white matter infarction. CMRO2 was elevated in stage II hemodynamic compromise (CVR < 10%, OEF > 50%). CVR and OEF showed a significant negative linear relationship in stage II hemodynamic compromise but revealed hemispheres in hemodynamic compromise by CVR but normal OEF that were associated with subcortical white matter infarction.
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PINTO JR, LUCIANO RIBEIRO, ADEMIR BAPTISTA SILVA, and SERGIO TUFIK. "Rapid eye movements during paradoxical sleep in patients with cerebrovascular disease." Arquivos de Neuro-Psiquiatria 58, no. 2A (June 2000): 239–45. http://dx.doi.org/10.1590/s0004-282x2000000200006.
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Rapid eye movements that occur during paradoxical sleep are generated from the brainstem and are modulated by cerebral hemispheres. In an attempt to establish the participation of cerebral hemispheres on rapid eye movements, we carried out a quantitative study of eye movements density in patients bearing hemispheres vascular lesions. The polysomnographic recordings of 24 patients were compared to those of 24 healthy volunteers. Density of rapid eye movements was defined as the porcentage of eye movements during the respective time of paradoxical sleep. Based on the present results, we concluded that: stroke patients with hemispheric lesions displayed increased density of rapid eye movements; there was no difference on the density of rapid eye movements according to the hemispheric lesion; higher density of rapid eye movements was observed in patients with anterior hemispheric lesion.
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Spivak, B., N. Karny, G. Katz, M. Radwan, A. Apter, R. Master, and A. Weizman. "Functional hemisphere imbalance in patients with paranoid or disorganized schizophrenia." European Psychiatry 11, no. 4 (1996): 175–79. http://dx.doi.org/10.1016/0924-9338(96)88387-8.
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SummaryWe assessed hemisphere function in right-handed male chronic schizophrenic patients using dichotic listening tests. We evaluated digit, tonic and transitional tests in patients with paranoid schizophrenia (n = 8), patients with disorganized schizophrenia (n = 8) and in control subjects (n = 8). The dichotic listening analysis discriminated between paranoid and disorganized schizophrenia. In disorganized schizophrenia, functional impairment of both hemispheres was demonstrated, while in paranoid schizophrenia dysfunction was more prominent in the right hemisphere. These results indicate the possible involvement of right hemisphere dysfunction in the pathophysiology of chronic paranoid schizophrenia, in contrast to dysfunction of both hemispheres in chronic disorganized schizophrenia.