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VI. Life’s Cerebral Faculties Become More Complex, Smarter, Informed, Proactive, Self-Aware

3. Laterality: A Bicameral Brain Emerges with the Nested Scales

Halpern, Marnie, et al. Lateralization of the Vertebrate Brain. Journal of Neuroscience. 25/45, 2005. Since the 1960s Nobel research of Roger Sperry, the extensive study of bicameral hemispheres not only in the human brain but throughout Metazoan kingdoms has lately coalesced upon a definitive picture. This survey article emphasizes zebrafish and pigeons, along with primates. The relegation of a detailed focus to the left side, with global context to the right is now found to hold constant for the course of life’s cerebral evolution, which reaches full expression in homo sapiens. This is a salient collaborative discovery, which has not yet registered, about nature’s complementary code. Indeed a further bilateral East/West and South/North Geo Sapiens phase is apparent as the Complementarity of Civilizations section document.

The long-held view that laterality is unique to the human cortex has been supplanted by overwhelming evidence of left-right differences in neuroanatomy and neural processing across vertebrate and even some invertebrate species. (10351) It might seem, therefore, that left-right differentiation of structure and function enhances the capacity of a brain across a wide range of species, regardless of species variation in neural capacity. (10355)

Hausmann, Markus, et al.. Laterality Entering the Next Decade: The 25th Anniversary of a Journal Devoted to Asymmetries of Brain, Behavior and Cognition. Laterality. 26/3, 2021. We cite this review/preview entry by Durham University (MH), Victoria University of Wellington (Gina Grinshaw) and University of New England, Australia (Lesley Rogers, search) scholars as a way in this late year to record the robust verification that has appeared on these scientific journal pages of an optimum bicameral asymmetry at each and every evolutionary phase and instance. As the citations note, and this resource documents, its vital occasion can be seen in effect from atomic light to (in)vertebrate animal organism all the ascendant way to our exemplary human faculties. Into these fraught 2020s, such an actual discovery of a natural complementarity between node - link, DNA – AND, dot – connect, me – We = US archetypes can now be achieved. As a result, it could at last bring these innate reciprocal attributes to inform and resolve political, engendered, combative, warlord cultures worldwide. In regard, Laterality remains the only journal of its kind dedicated to gather and report and this once and future Yang + Yin = Taome optimum poise,

In 1996, Phil Bryden, Mike Corballis, and Chris McManus released the first issue of Laterality. These founding editors pointed out in their editorial how surprisingly long it took to have a journal devoted entirely to laterality, its unanswered questions and wide-ranging problems. They mentioned left-right asymmetries inside sub-atomic structures, the pharmacology of chiral molecules, anatomical asymmetries of the viscera, Broca's discovery of the left-brain dominance in language production, and so on. One-hundred and twenty-eight issues later, Laterality celebrates with a special Issue: Laterality research entering the next decade. It opens with an opinion paper by Sebastian Ocklenburg, et al which outlines ten trends going forward into the 2020s. (Excerpts)

In the 2010s, significant progress has been made in key areas including neuroimaging, genetics and comparative research. Here, we discuss which trends which may shape laterality research in the 2020s such as ntegrating cross-cultural samples, combined meta-analysis and databank studies, the treatment of psychiatric and neurodevelopmental disorders, molecular correlates of environmental factors, graph-theory and machine learning method and so on. These disparate aspects will open the way for novel questions, enhanced collaborations and boost the reliable validity of evidential findings for this widely pervasive cerebral and cognitive feature. (Ocklenburg excerpt)

It is surprising how long it has taken to have a journal devoted entirely to Lateriality. Left-right asymmetries appear at almost all level of scientific endeavor from deep inside sub-atomic structures, through to the biochemistry of dextral sugars and animo-acids, to chiral molecules, and onto the intrinsic asymmetry of brains and language and galactic handedness. (Initial issue editorial excerpt, 1/1, 1996)

Laterality: Asymmetries of Brain, Behaviour, and Cognition publishes high quality research on all these aspects of human and non-human (vertebrate and invertebrate) species, including its psychological, behavioural, neural, genetic or other biological manifestations. The field of laterality is broad so the editors will consider papers which also illuminate the evolution of biological, neural, or behavioural asymmetry; papers on cultural, linguistic, artistic, and social expressions; as well as on its development, function, and historical origins.

Hopkins, William D. and Claudio Cantalupo. Theoretical Speculations on the Evolutionary Origins of Hemispheric Specialization. Current Directions in Psychological Science. 17/3, 2010. Until a few years ago, the presence of bilateral brain asymmetries in any species other than ourselves was ruled out. In this paper Yerkes National Primate Research Center psychologists summarize findings that indeed affirm a consistent division of Metazoan cerebral faculties into parallel halves. Moreover the same generic, archetypal complements of left detailed part and right spatial image that hold for humans is similarly evident throughout creaturely life. So evolution appears to have figured out early on that two brains with such alternative abilities are better than one. And if there is a ramifying continuum, it might be the size of the interconnecting corpus callosum bundle of fibers, which are less manifest in primates and mammals.

In the past 30 years, the very anthropocentric view that hemispheric specialization is unique to humans has been challenged on both the behavioral and neurological level. For example, left-hemisphere asymmetries in the processing of species-specific signals have now been documented in birds, frogs, mice, rats, and nonhuman primates. Differential involvement of the cerebral hemispheres in the discrimination of visual stimuli on the basis of global configuration (which shows right-hemisphere advantage) or local features (which show left-hemisphere advantage) has been reported in birds and nonhuman primate species. Evidence of right-hemisphere bias in emotional processing has also been reported in many species, including toads, birds, rats, and nonhuman primates. (233)

One possible interpretation of the existing findings is that the overall pattern of convergence in directionality of population level asymmetry across different vertebrate species reflects homology (i.e., shared ancestry) in laterality dating back many millions of years. However, an alternative interpretation of the continuity of asymmetry patterns across vertebrate species involves the principle of homoplasy—that is, convergent evolution. In other words, common patterns of asymmetries in humans and other species may have evolved independently and potentially through different selection pressures. (234)

Hopkins, William D., ed. The Evolution of Hemispheric Specialization in Primates. London: Academic Press, 2008. With lead chapters about “Cerebral Asymmetry and Human Uniqueness” by Michael Corballis, and Lesley Rogers’ “Lateralization in Its Many Forms, and Its Evolution and Development,” further confirmations are announced that a complementary bicameral brain of much survival advantage can indeed be consistently traced through life’s long gestation.

Kahn, Meghan and Verner Bingman. Lateralization of Spatial Learning in the Avian Hippocampal Formation. Behavioral Neuroscience. 118/2, 2004. Similar to the mammalian hippocampus with its functions of learning and memory, a bilateral asymmetry in birds repeats the same right preference for holistic survey and left attention to detail.

Our work has specifically shown that the right HF of birds is preferentially sensitive to global spatial information, whereas the left HF appears capable of encoding spatial relations among more proximal, local cues with in environment. (343)

Karenina, Karina, et al. Lateralization of Mother-Infant Interactions in a Diverse Range of Mammal Species. Nature Ecology & Evolution. 1/0030, 2017. In this new online journal, St. Petersburg State University, University of Utah, and University of Tasmania ecological zoologists again find a consistent right brain preference from reindeer and sheep to walrus, whales, and kangaroos for their visual interactions with young offspring. See also Continuities in Emotion Lateralization in Human and Non-Human Primates by Annukka Lindell in Frontiers in Human Neuroscience (Vol. 7/Art. 464, 2013) and Mammal Mothers and Infants Prefer the Position Favouring Right Hemisphere Processing by Andrey Giljov, et al in Biology Letters (14/1, 2018).

Left-cradling bias is a distinctive feature of maternal behaviour in humans and great apes, but its evolutionary origin remains unknown. In 11 species of marine and terrestrial mammal, we demonstrate consistent patterns of lateralization in mother–infant interactions, indicating right hemisphere dominance for social processing. In providing clear evidence that lateralized positioning is beneficial in mother–infant interactions, our results illustrate a significant impact of lateralization on individual fitness. (Abstract)

Letzkus, Pinar, et al. Lateralization of Visual Learning in the Honeybee. Biology Letters. 4/1, 2008. One of the first confirmations that even insect invertebrates possess and display an effective neural lateralization.

Letzner, Sara, et al. Visuospatial Attention in the Lateralized Brain of Pigeons. Nature Scientific Reports. 7/15547, 2017. By way of clever tests with regard to eye-preference for pecking peas due to light exposure, Ruhr-University Bochum and University of Duisburg-Essen biopsychologists including Onur Gunturkun add further proof of life’s constant bicameral left detail focus and right field of view across animal kingdoms to our exemplary human phase. A critical aspect is then said to be a dynamic interplay of inter-hemispheric processes.

A typical right-hemispheric specialisation is spatial attention. In humans, lateralised attention control is shown in a visuospatial bias to the left hemispace in line-bisection, or cancellation tasks and enhanced right-hemispheric activation is supported by neuro-imaging and neurophysiological studies. Birds display a similar leftward bias in their pecking activity in a food detection task in which they are required to explore an area uniformly spread with grains. This pattern suggests a right-hemispheric dominance for controlling visuospatial attention. (2)

Levin, Michael, et al. Introduction to Provocative Questions in Left-Right Asymmetry. Philosophical Transactions of the Royal Society B. Vol. 371/Iss. 1710, 2016. Tufts University, National Cancer Institute, and University of South Carolina biologists survey this theme issue about life’s organismic and evolutionary propensities for a bilateral balance of somatic forms and morphodynamic processes. As the second quote cites, from another angle a Yin and Yang complementarity is observed across corporeal creatures and Metazoic eras. Typical papers are What Determines the Direction of Asymmetry, Embryonic Chirality and the Evolution of Spiralian Left-Right Asymmetries, and Nodal Signalling and Asymmetry of the Nervous System.

Left–right asymmetry is a phenomenon that has a broad appeal—to anatomists, developmental biologists and evolutionary biologists—because it is a morphological feature of organisms that spans scales of size and levels of organization, from unicellular protists, to vertebrate organs, to social behaviour. Here, we highlight a number of important aspects of asymmetry that encompass several areas of biology—cell-level, physiological, genetic, anatomical and evolutionary components—and that are based on research conducted in diverse model systems, ranging from single cells to invertebrates to human developmental disorders. Together, the contributions in this issue reveal a heretofore-unsuspected variety in asymmetry mechanisms, including ancient chirality elements that could underlie a much more universal basis to asymmetry development, and provide much fodder for thought with far reaching implications in biomedical, developmental, evolutionary and synthetic biology. (Abstract)

From the nano to the macro, the man-made to the natural and the simple to the complex, the world we inhabit is rich in pattern. Although there is extensive variance in the intricacy and magnitude of the patterns that surround us, they fundamentally stem from only two core motifs: symmetry and asymmetry. Prevalent in our art, architecture, dance, music, fashion and other design—symmetry evokes order, desire, harmony and perfection. Together, symmetry and asymmetry comprise the proverbial Yin and Yang, the black and white, the metaphorical good and sinister. Both are essential for completeness, but too much in either direction disrupts a critical balance—symmetry unchecked by asymmetry transmutes order, harmony and beauty into static, sterile and monotonous. Asymmetry unchecked by symmetry becomes aberrant, unrestrained and chaotic. (1)

MacNeilage, Peter. Towards a Unified View of Cerebral Hemispheric Specializations in Vertebrates. David Milner, ed. Comparative Neuropsychology. New York: Oxford University Press, 1998. As a general rule the right hemisphere processes a topological, holistic aspect while the left attends to specific, localized details.

I have argued that there have arisen complementary intrahemispheric input/output specializations for particular purposes - a left-side rapid response specialization directly linked to right hemisphere input apprehension specialization. (177)

MacNeilage, Peter, et al. Origins of the Left & Right Brain. Scientific American. July, 2009. This outline section has documented for some years how researchers are finding that a bilateral brain with characteristic right and left hemispheres is not uniquely human, rather it occurs across the animal kingdoms and deep into their evolutionary origins. With co-authors Lesley Rogers and Giorgio Vallortigara, the case is made that this discovery is ready for prime time. What is then significant is not only a 500 million year old vertebrate asymmetric brain selected for effective survival, but that the archetypal image/object complementarity is maintained for primates, mammals, birds, amphibians, fish, and even invertebrate insects (not here noted). Altogether another prime instance of the universal yin and yang present in the ramifying cerebral faculties in each and every creature.

In the human brain the left hemisphere controls language, the dexterity of the right hand, the ability to classify, and routine behavior in general. The right hemisphere specializes in reacting to emergencies, organizing items spatially, recognizing faces and processing emotions. (60) The left hemisphere of the human brain controls language, arguably our greatest mental attribute. It also controls the remarkable dexterity of the human right hand. The right hemisphere is dominant in the control of, among other things, our sense of how objects interrelate in space. (60) In the vertebrate nervous system the connections cross between body and brain—to a large degree, nerves to and from one side of the body are linked to the opposite-side hemisphere of the brain. (62)

Manns, Martina, et al. It Takes Two to Tango: Hemispheric Integration in Pigeons Requires Both Hemispheres to Solve a Transitive Inference Task. Animal Behavior. 126/231, 2017. As the quote reviews, in these later 2010s Ruhr-University Bochum and University of Hagen, Germany biopsychologists can draw a decade and more of research findings, along with their own avian studies, to evince the beneficial presence throughout animal kingdoms including invertebrates of complementary cerebral faculties. We ought to then remind that these scientific achievements are well confirming a common, archetypal hemispheric of left side detail and right half image. A further notice is their bicameral occurrence from life’s earliest evolution of a neural system.

A growing number of examples show that the left and right brain halves play differential roles in controlling behavior not only in humans but also in other vertebrates and even in invertebrates. These cerebral asymmetries are presumably caused by differences in the preferential processing mode of the two brain halves and are based on structural variances between left- and right-hemispheric neuronal circuits. Several models suggest general encoding asymmetries that are shared by different vertebrate species and hence may have an evolutionary origin. Hemispheric asymmetries might be traced back to a left-hemispheric specialization for routine behavior and feeding and a right-hemispheric dominance for the detection of unexpected stimuli and control behaviors in emergency situations. In relation to this basic lateralization pattern, the left hemisphere is specialized to adopt a feature-based strategy by relying on local aspects of stimuli and extracting the common elements of individual stimulus patterns. In contrast, the right hemisphere preferentially encodes global information and responds to novelty. Consequently, left-and right-hemispheric networks eventually process information in their specialized relatively independent ways. (231)

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