VI. Life’s Cerebral Cognizance Becomes More Complex, Smarter, Informed, Proactive, Self-Aware

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

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)

Mithen, Steven. The Music Instinct: The Evolutionary Basis of Musicality. Annals of the New York Academy of Sciences. Vol. 1169, 2009. A keynote for the proceedings of The Neurosciences and Music III conference, which is a succinct capsule of Mithen’s 2006 book The Singing Neanderthals. The melodic reprise is a recurrence across life’s procession and humanity’s passage, and for each of us, from an holistic originality unto discrete alphabetic signals, as a course from right to left brain modes.

Moskovitz, Ted, et al. A Unified Theory of Dual-Process Control. arXiv:2211.07036. University College London computational neuroscientists including Mathew Botvinick adds a latest veracity to understandings that our human cognizance relies on two archetypal mental modes, as do animal realms. If one might try to broach, they might be fast and frugal, discrete and terse and in contrast an avail of integral vistas and rationales. See also Reinforcement Learning, Fast and Slow by M. Botvinick, et al in Trends in Cognitive Sciences (23/408, 2019). Once again these bicameral, binaural complements are found in active effect everywhere as evidence ever builds for their universal, bigender presence.

Dual-process theories play a central role in both psychology and neuroscience in fields ranging from executive control to reward-based learning to judgment and decision making. In each of these domains, two mechanisms appear to operate concurrently, one relatively high in computational complexity, the other relatively simple. Why is neural information processing organized in this way? We propose an answer based on the notion of compression. The key insight is that dual-process structure can enhance adaptive behavior by allowing an agent to minimize the description length of its own behavior. We apply a basic model to show that diverse dual-process phenomena can yet be understood as domain-specific consequences of a single underlying set of computational principles. (Excerpt)

Namigai, Erica, et al. Right Across the Tree of Life: The Evolution of Left-Right Asymmetry in the Bilateria. Genesis. 52/458, 2014. In an issue on Left-Right Asymmetry: Advances and Enigmas, Oxford University zoologists trace this ubiquitous neural formation to embryonic “nodal signaling” by proteins that govern pattern differentiations. See also in this issue Left-Right Asymmetry in the Sea Urchin and Asymmetry of Brain and Behavior in Animals.

Quin-Conroy, Josephine, et al.. Patterns of language and visuospatial functional lateralization and cognitive ability. Laterality. September, 2023. University of Western Australia linguists contribute a latest quantified affirmation of nature’s archetypal hemispheric preferences. Once again we wonder however these verse and vision complements could be known well enough such that they might apply to political parties.

For most individuals, language is predominately localized to the left hemisphere of the brain and visuospatial processing to the right. Evolutionary theories of lateralization suggest that this typical pattern is most common as it delivers a cognitive advantage. In contrast, deviations from the typical pattern may lead to poorer cognitive abilities. The aim of this systematic review was to assess the evidence for an association between patterns of language and visuospatial lateralization and measures of cognitive ability. (Excerpt).

University of Western Australia Just 10 minutes from Perth city, UWA is located on the banks of the Swan River on the land of the Whadjuk Nation. We have the privilege of being on sacred soil where Western Australian kaartdijin, or knowledge, began. It has been a place to gather and learn for tens of thousands of years by the world’s oldest continuous culture.

Rogers, Lesley and Giorgio Vallortigara. When and Why Did Brains Break Symmetry? Symmetry. 7/2181, 2015. This section seeks to report an increasing array of findings over the past two decades that an asymmetric bilateral neural architecture distinguishes not only human beings but every Metazoan vertebrate and invertebrate creature. As this online article avers, it is present from fowl to fish to insects. This constant, reciprocal form can also be traced to the earliest evolutionary rudiments. The University of New England, Australia, and University of Trento, Italy researchers have been leading proponents and wrote Divided Brains in 2013. In this 2015 survey, it is averred that the same complementary left focus and right field hemispheric attributes are similarly in place for every species. The presence of such a common cerebral structure, unknown until the 1990s, is an auspicious discovery about life’s emergent development. By still another feature, a ramifying, elaborating gestation from its origin gains validity. And if to turn and project forward, a major transition underway to a global humankinder can be seen to have comparable east/west and south/north halves.

Rogers, Lesley and Giorgio Vallortigara, eds. Lateralized Brain Functions: Methods in Human and Non-Human Species. Switzerland: Springer, 2017. The editors (search) are leading researchers for this robust 21st century realization that asymmetric bicameral neural attributes extend all the way through life’s creaturely evolution to the first sensory onsets. Some chapters are Lateralization in Invertebrates by Elisa Frasnelli, and Genetics of Human Handedness and Laterality by Silvia Paracchini.

This volume explores both simple and sophisticated techniques used in the study of different types of lateralization of brain and behavior. It is divided into five parts: behavioral methods; neurobiological methods; electroencephalographic, imaging, and neuro-stimulation methods; genetic techniques; and development of lateralization. Part I addresses measuring lateralization by scoring behavior induced by inputs to one or the other side of the brain in a range of species. Part II covers neurobiological methods used to reveal lateralization, such as lesion studies, electrophysiology and pharmacology, early gene expression, and new optogenetic methods. Part III looks at imaging techniques, electroencephalographic techniques, and transcranial stimulation to reveal lateralization. Part IV describes techniques used to study the role of genes in the development and establishment of brain asymmetry in humans and other species. Lastly, Part V refers to methods used in the study of development of lateralization through the manipulation of sensory exposure, hormone levels, and in model systems.

Rogers, Lesley and Giorgio Vallortigara, eds. Lateralized Brain Functions: Methods in Human and Non-Human Species.. Switzerland: Springer,, 2025. The University of New England, Australia and University of Trento, Italy editors are senior definers (search) of this 21st century project to realize and thoroughly quantify the evolutionary occurrence and emergent ramification of complementary hemispheres and their common archetypes. This volume adds the latest methods and evidence such as Lateralization in Invertebrates by Davide Liga and Elisa Frasnelli and Reversals of Bodies, Brains, and Behavior: Quantitative Analysis of Laterality by Douglas Blackiston and Michael Levin.

The chapters in this book cover topics such as measuring lateralization in a range of species by scoring behavior elicited by inputs to one of both brain hemispheres; behavioral studies of motor preferences; neurological methods to reveal lateralization; imaging and new genetic approaches to studying humans and zebrafish.

Rogers, Lesley and Richard Andrew, eds. Comparative Vertebrate Lateralization. Cambridge: Cambridge University Press, 2002. A voluminous summary of research studies on bilateral brain asymmetry in fish, birds, mammals and primates. What was long thought to be only a human attribute is now realized to extend throughout the evolution of animals. Moreover the same characteristics appear to hold for each hemisphere. The right side surveys the overall scene or forest while the left discerns separate objects or trees. The right half ponders and the left responds. As a consequence, these archetypal complementarities seem to be present in brain anatomies and behaviors from their evolutionary origin.

The resemblance to human dichotomies of hemispheric function is obvious. The Rhem shows diffuse or global attention, spatial analysis and no special involvement in control of response. The Lhem shows focused attention, recording of local cues and control of response. (96)

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