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Abstract
Asymmetries in the functional and structural organization of the nervous system are widespread in the animal kingdom and especially characterize the human brain. Although there is little doubt that asymmetries arise through genetic and nongenetic factors, an overarching model to explain the development of functional lateralization patterns is still lacking. Current genetic psychology collects data on genes relevant to brain lateralizations, while animal research provides information on the cellular mechanisms mediating the effects of not only genetic but also environmental factors. This review combines data from human and animal research (especially on birds) and outlines a multi-level model for asymmetry formation. The relative impact of genetic and nongenetic factors varies between different developmental phases and neuronal structures. The basic lateralized organization of a brain is already established through genetically controlled embryonic events. During ongoing development, hemispheric specialization increases for specific functions and subsystems interact to shape the final functional organization of a brain. In particular, these developmental steps are influenced by environmental experiences, which regulate the fine-tuning of neural networks via processes that are referred to as ontogenetic plasticity. The plastic potential of the nervous system could be decisive for the evolutionary success of lateralized brains.
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Letzner S, Manns M, Güntürkün O. Light-dependent development of the tectorotundal projection in pigeons. Eur J Neurosci 2020; 52:3561-3571. [PMID: 32386351 DOI: 10.1111/ejn.14775] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 04/22/2020] [Accepted: 05/04/2020] [Indexed: 12/13/2022]
Abstract
Left-right differences in the structural and functional organization of the brain are widespread in the animal kingdom and develop in close gene-environment interactions. The visual system of birds like chicks and pigeons exemplifies how sensory experience shapes lateralized visual processing. Owing to an asymmetrical posture of the embryo in the egg, the right eye/ left brain side is more strongly light-stimulated what triggers asymmetrical differentiation processes leading to a left-hemispheric dominance for visuomotor control. In pigeons (Columba livia), a critical neuroanatomical element is the asymmetrically organized tectofugal pathway. Here, more fibres cross from the right tectum to the left rotundus than vice versa. In the current study, we tested whether the emergence of this projection asymmetry depends on embryonic light stimulation by tracing tectorotundal neurons in pigeons with and without lateralized embryonic light experience. The quantitative tracing pattern confirmed higher bilateral innervation of the left rotundus in light-exposed and thus, asymmetrically light-stimulated pigeons. This was the same in light-deprived pigeons. Here, however, also the right rotundus received an equally strong bilateral input. This suggests that embryonic light stimulation does not increase bilateral tectal innervation of the stronger stimulated left but rather decreases such an input pattern to the right brain side. Combined with a morphometric analysis, our data indicate that embryonic photic stimulation specifically affects differentiation of the contralateral cell population. Differential modification of ipsi- and contralateral tectorotundal connections could have important impact on the regulation of intra- and interhemispheric information transfer and ultimately on hemispheric dominance pattern during visual processing.
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Affiliation(s)
- Sara Letzner
- Department of Psychology, Institute of Cognitive Neuroscience, Biopsychology, Ruhr-University of Bochum, Bochum, Germany
| | - Martina Manns
- Division of Experimental and Molecular Psychiatry, Department of Psychiatry, Psychotherapy and Preventive Medicine, Ruhr-University Bochum, Bochum, Germany
| | - Onur Güntürkün
- Department of Psychology, Institute of Cognitive Neuroscience, Biopsychology, Ruhr-University of Bochum, Bochum, Germany
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Schmitz J, Fraenz C, Schlüter C, Friedrich P, Kumsta R, Moser D, Güntürkün O, Genç E, Ocklenburg S. Schizotypy and altered hemispheric asymmetries: The role of cilia genes. Psychiatry Res Neuroimaging 2019; 294:110991. [PMID: 31683112 DOI: 10.1016/j.pscychresns.2019.110991] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/27/2022]
Abstract
Schizophrenia patients have a higher probability of altered structural and functional differences between the left and right hemisphere. Schizotypy as its nonclinical manifestation has been related to a higher incidence of non-right-handedness and atypical right-hemispheric language dominance. It has been suggested that genes involved in cilia function might link brain asymmetry and neurodevelopmental disorders. We assessed DNA methylation in the promoter regions of seven candidate genes involved in cilia function and psychiatric disorders from buccal cells and investigated their association with schizotypy and language lateralization in 60 healthy adults. Moreover, we determined microstructural properties of the planum temporale in a subsample of 52 subjects using neurite orientation dispersion and density imaging (NODDI). We found a significant association between schizotypy and DNA methylation in the AHI1 promoter region. Moreover, AHI1 DNA methylation significantly predicted language lateralization and asymmetry in estimated planum temporale neurite density. Finally, stronger leftward asymmetry in estimated neurite density was associated with a more pronounced right ear advantage (left hemisphere dominance) in the forced-right condition of the dichotic listening task, measuring attentional modulation of language lateralization. Our results are in line with a shared molecular basis of schizotypy and functional hemispheric asymmetries that is based on cilia function.
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Affiliation(s)
- Judith Schmitz
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany.
| | - Christoph Fraenz
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany
| | - Caroline Schlüter
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany
| | - Patrick Friedrich
- Brain Connectivity and Behaviour Laboratory (BCBLab), Sorbonne Universities, Paris, France; Groupe d'Imagerie Neurofonctionnelle (GIN), Institut des Maladies Neurodégénératives-UMR 5293, CNRS, CEA University of Bordeaux, Bordeaux, France
| | - Robert Kumsta
- Genetic Psychology, Department of Psychology, Ruhr University, Bochum, Germany
| | - Dirk Moser
- Genetic Psychology, Department of Psychology, Ruhr University, Bochum, Germany
| | - Onur Güntürkün
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany
| | - Erhan Genç
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany
| | - Sebastian Ocklenburg
- Biopsychology, Institute of Cognitive Neuroscience, Department of Psychology, Ruhr University, Bochum, Germany
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Schmitz J, Metz GA, Güntürkün O, Ocklenburg S. Beyond the genome—Towards an epigenetic understanding of handedness ontogenesis. Prog Neurobiol 2017; 159:69-89. [DOI: 10.1016/j.pneurobio.2017.10.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 09/18/2017] [Accepted: 10/26/2017] [Indexed: 12/13/2022]
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Letzner S, Güntürkün O, Lor S, Pawlik RJ, Manns M. Visuospatial attention in the lateralised brain of pigeons - a matter of ontogenetic light experiences. Sci Rep 2017; 7:15547. [PMID: 29138476 PMCID: PMC5686156 DOI: 10.1038/s41598-017-15796-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022] Open
Abstract
The ontogenetic mechanisms leading to complementary hemispheric specialisations of the two brain halves are poorly understood. In pigeons, asymmetrical light stimulation during development triggers the left-hemispheric dominance for visuomotor control but light effects on right-hemispheric specialisations are largely unknown. We therefore tested adult pigeons with and without embryonic light experience in a visual search task in which the birds pecked peas regularly scattered on an area in front of them. Comparing the pecking pattern of both groups indicates that the embryonic light conditions differentially influence biased visuospatial attention under mono- and binocular seeing conditions. When one eye was occluded, dark-incubated pigeons peck only within the limits of the visual hemifield of the seeing eye. Light-exposed pigeons also peck into the contralateral field indicating enlarged monocular visual fields of both hemispheres. While dark-incubated birds evinced an attentional bias to the right halfspace when seeing with both eyes, embryonic light exposure shifted this to the left. Thus, embryonic light experience modifies processes regulating biased visuospatial attention of the adult birds depending on the seeing conditions during testing. These data support the impact of light onto the emergence of functional dominances in both hemispheres and point to the critical role of interhemispheric processes.
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Affiliation(s)
- Sara Letzner
- Biopsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum, 44780, Bochum, Germany.,Cognitive Neurophysiology, Department of Child and Adolescent Psychiatry, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany
| | - Onur Güntürkün
- Biopsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Stephanie Lor
- Biopsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum, 44780, Bochum, Germany
| | - Robert Jan Pawlik
- Institute of Medical Psychology and Behavioral Immunobiology, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Martina Manns
- Biopsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum, 44780, Bochum, Germany.
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Yoo HN, Lee JW, Yoo JC. Asymmetry of eye color in the common cuckoo. Sci Rep 2017; 7:7612. [PMID: 28790375 PMCID: PMC5548743 DOI: 10.1038/s41598-017-08071-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 07/06/2017] [Indexed: 11/09/2022] Open
Abstract
Bilateral symmetry is assumed to contribute to the evolution of eye color, with the left and right eye being the same color in most vertebrates; yet, few studies tested this assumption. Here, we compared the amount of iris flecking (black spots presented on the iris) between the left and right eye of 76 adult common cuckoos Cuculus canorus. We found considerable variation in the total amount of iris flecking among individuals, with variation being associated with body size and sex. We also found that the amount of iris flecking differed between the left and right eye and that this left-right asymmetry was not random, with the left eye almost always being darker than the right eye. Furthermore, this asymmetry was negatively associated with wing length; however, this effect was limited to individuals with dark eyes. Overall, the asymmetric, but non-random, distribution of iris flecking between the left and right eye may indicate that selection pressures driving asymmetry (such as visual lateralization) act on the development of iris colors, even though this effect might be limited, due to the role of bilateral symmetry.
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Affiliation(s)
- Ha-Na Yoo
- Korea Institute of Ornithology & Department of Biology, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Jin-Won Lee
- Korea Institute of Ornithology & Department of Biology, Kyung Hee University, Seoul, 02447, Republic of Korea.
| | - Jeong-Chil Yoo
- Korea Institute of Ornithology & Department of Biology, Kyung Hee University, Seoul, 02447, Republic of Korea
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Ocklenburg S, Schmitz J, Moinfar Z, Moser D, Klose R, Lor S, Kunz G, Tegenthoff M, Faustmann P, Francks C, Epplen JT, Kumsta R, Güntürkün O. Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetries. eLife 2017; 6. [PMID: 28145864 PMCID: PMC5295814 DOI: 10.7554/elife.22784] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Accepted: 01/31/2017] [Indexed: 12/11/2022] Open
Abstract
Lateralization is a fundamental principle of nervous system organization but its molecular determinants are mostly unknown. In humans, asymmetric gene expression in the fetal cortex has been suggested as the molecular basis of handedness. However, human fetuses already show considerable asymmetries in arm movements before the motor cortex is functionally linked to the spinal cord, making it more likely that spinal gene expression asymmetries form the molecular basis of handedness. We analyzed genome-wide mRNA expression and DNA methylation in cervical and anterior thoracal spinal cord segments of five human fetuses and show development-dependent gene expression asymmetries. These gene expression asymmetries were epigenetically regulated by miRNA expression asymmetries in the TGF-β signaling pathway and lateralized methylation of CpG islands. Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness, implying a fundamental shift in our understanding of the ontogenesis of hemispheric asymmetries in humans. DOI:http://dx.doi.org/10.7554/eLife.22784.001
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Affiliation(s)
- Sebastian Ocklenburg
- Institute of Cognitive Neuroscience, Department Biopsychology, Ruhr University Bochum, Bochum, Germany
| | - Judith Schmitz
- Institute of Cognitive Neuroscience, Department Biopsychology, Ruhr University Bochum, Bochum, Germany
| | - Zahra Moinfar
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Bochum, Germany
| | - Dirk Moser
- Department of Genetic Psychology, Ruhr University Bochum, Bochum, Germany
| | - Rena Klose
- Institute of Cognitive Neuroscience, Department Biopsychology, Ruhr University Bochum, Bochum, Germany
| | - Stephanie Lor
- Institute of Cognitive Neuroscience, Department Biopsychology, Ruhr University Bochum, Bochum, Germany
| | - Georg Kunz
- Department of Obstetrics and Gynecology, St. Johannes Hospital, Dortmund, Germany
| | - Martin Tegenthoff
- Department of Neurology, University Hospital Bergmannsheil, Bochum, Germany
| | - Pedro Faustmann
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Bochum, Germany
| | - Clyde Francks
- Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands
| | - Jörg T Epplen
- Department of Human Genetics, Ruhr University Bochum, Bochum, Germany
| | - Robert Kumsta
- Department of Genetic Psychology, Ruhr University Bochum, Bochum, Germany
| | - Onur Güntürkün
- Institute of Cognitive Neuroscience, Department Biopsychology, Ruhr University Bochum, Bochum, Germany.,Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch, South Africa
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Manns M, Ströckens F. Functional and structural comparison of visual lateralization in birds - similar but still different. Front Psychol 2014; 5:206. [PMID: 24723898 PMCID: PMC3971188 DOI: 10.3389/fpsyg.2014.00206] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 02/24/2014] [Indexed: 11/21/2022] Open
Abstract
Vertebrate brains display physiological and anatomical left-right differences, which are related to hemispheric dominances for specific functions. Functional lateralizations likely rely on structural left-right differences in intra- and interhemispheric connectivity patterns that develop in tight gene-environment interactions. The visual systems of chickens and pigeons show that asymmetrical light stimulation during ontogeny induces a dominance of the left hemisphere for visuomotor control that is paralleled by projection asymmetries within the ascending visual pathways. But structural asymmetries vary essentially between both species concerning the affected pathway (thalamo- vs. tectofugal system), constancy of effects (transient vs. permanent), and the hemisphere receiving stronger bilateral input (right vs. left). These discrepancies suggest that at least two aspects of visual processes are influenced by asymmetric light stimulation: (1) visuomotor dominance develops within the ontogenetically stronger stimulated hemisphere but not necessarily in the one receiving stronger bottom-up input. As a secondary consequence of asymmetrical light experience, lateralized top-down mechanisms play a critical role in the emergence of hemispheric dominance. (2) Ontogenetic light experiences may affect the dominant use of left- and right-hemispheric strategies. Evidences from social and spatial cognition tasks indicate that chickens rely more on a right-hemispheric global strategy whereas pigeons display a dominance of the left hemisphere. Thus, behavioral asymmetries are linked to a stronger bilateral input to the right hemisphere in chickens but to the left one in pigeons. The degree of bilateral visual input may determine the dominant visual processing strategy when redundant encoding is possible. This analysis supports that environmental stimulation affects the balance between hemispheric-specific processing by lateralized interactions of bottom-up and top-down systems.
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Affiliation(s)
- Martina Manns
- Department of Biopsychology, Institute of Cognitive Neuroscience, Faculty of Psychology, Ruhr-University Bochum Bochum, Germany
| | - Felix Ströckens
- Department of Biopsychology, Institute of Cognitive Neuroscience, Faculty of Psychology, Ruhr-University Bochum Bochum, Germany
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Shaping a lateralized brain: asymmetrical light experience modulates access to visual interhemispheric information in pigeons. Sci Rep 2014; 4:4253. [PMID: 24584671 PMCID: PMC3939453 DOI: 10.1038/srep04253] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 02/10/2014] [Indexed: 11/09/2022] Open
Abstract
Cerebral asymmetries result from hemispheric specialization and interhemispheric communication pattern that develop in close gene-environment interactions. To gain a deeper understanding of developmental and functional interrelations, we investigated interhemispheric information exchange in pigeons, which possess a lateralized visual system that develops in response to asymmetrical ontogenetic light stimulation. We monocularly trained pigeons with or without embryonic light experience in color discriminations whereby they learned another pair of colors with each eye. Thereby, information from the ipsilateral eye had to be transferred. Monocular tests confronting the animals with trained and transferred color pairs demonstrated that embryonic light stimulation modulates the balance of asymmetrical handling of transfer information. Stronger embryonic stimulation of the left hemisphere significantly enhanced access to interhemispheric visual information, thereby reversing the right-hemispheric advantage that develops in the absence of embryonic light experience. These data support the critical role of environmental factors in molding a functionally lateralized brain.
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Manns M, Römling J. The impact of asymmetrical light input on cerebral hemispheric specialization and interhemispheric cooperation. Nat Commun 2012; 3:696. [DOI: 10.1038/ncomms1699] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 01/24/2012] [Indexed: 11/09/2022] Open
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Manns M, Güntürkün O. Dual coding of visual asymmetries in the pigeon brain: the interaction of bottom-up and top-down systems. Exp Brain Res 2009; 199:323-32. [DOI: 10.1007/s00221-009-1702-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 01/02/2009] [Indexed: 11/25/2022]
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