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 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)

Rogers, Lesley, et al. Divided Brains: The Biology and Behaviour of Brain Asymmetries. Cambridge: Cambridge University Press, 2013. The issue of whether human cerebral hemisphere asymmetries are unique to us or have a deep evolutionary heritage began to be engaged in the 1980s with primates. In the interim, as this section and A Complementary Brain and Thought Process documents, researchers have extended studies to every vertebrate mammalian, avian, reptilian, aquatic, and invertebrate crustacean and insect kingdoms. In this volume, leading authorities Rogers, University of New England, Australia, Giorgio Vallortigara, University of Trento, and Richard Andrew, University of Sussex, (search each also) can now affirm a robust continuity of bicameral brains from urchins to sapiens. As so filled in, life’s long neural development appears as a singular, bicameral encephalization. With monkeys, chickens, and zebrafish as helpful subjects, the archetypal attributes of a Left fine, particulate focus and Right global, integral survey are found to be maintained at every prior, rudimentary instance. Notably, this work by neuroscientists goes on to attest, in the third quote, to a strong gender basis for these side by side penchants, with the notice that women avail a more balanced thought process. In closing, reference is made to Iain McGilchrist’s 2009 treatise which contends that every aspect of human society for better or worse can be traced to these hemispherical complements.

To sum up, a common pattern of lateralization is apparent among vertebrate species. Briefly, the left hemisphere is specialized to attend to similarities or invariances between stimuli, in order to allocate stimuli in categories following rules established through experience or biological predispositions. The left hemisphere shows focused attention, in particular to local features of the environment, so that the animal is not easily distracted by extraneous stimuli. The right hemisphere, on the other hand, attends to novel stimuli (variance). It notices unique and small differences between stimuli and, as an aspects of this specialization, it is easily distracted from the task being performed. The right hemisphere shows diffuse attention making it specialized to attend to the global rather than the local properties of stimuli, as shown both in spatial and social. (27-28)

Hemispheric Interaction A key feature of advanced mammals is the evolution of the corpus callosum, which connects both corresponding and different areas of the left and right cortices. Initially in evolution, corpus callosum may have no more than supplemented the left-right connections provided by the anterior and tectal commissures in other vertebrates. However, the shorter route between the hemispheres, provided by the corpus callosum, extending as it does for much of the length of the dorsal surface of the brain, must have progressively allowed more and more extensive fast interaction between the left and right forebrain. (143)

Sex Differences and Hormones These findings suggest that testosterone-treated chicks are strongly dependent on the left hemisphere as they search for food. Testosterone may promote the ability of the left hemisphere to sustain use of recently acquired information, as part of its role in keeping to a course of action. At the same time the left hemisphere of testosterone-treated chicks appears to reduce its inhibition of the right hemisphere, and to elevate aggressive and sexual behavior. (145) In general men perform better than women on feature separation tests, requiring attention to a selected feature. In such tests an ability to separate the path of a moving object from a background may be measured. Women are generally more likely to show collaboration between the two hemispheres rather than suppression of the abilities of the right by the goals of the left. Women perform better than men when it is necessary to remember object identity within an array. If the spatial layout is unchanged but some pairs of objects are exchanged, women are better at detecting this. Comparable female advantage is shown in episodic memory. This holds for a wide range of memories: newly acquired facts, the range of different activities carried out in a session, face recognition, and verbal tasks. Both these examples of female superiority would be explained by more effective use of the abilities of the right hemisphere for accessing memory of patterns made up of multiple items, owing to lesser intervention of the left hemisphere. (145-146)

In his comprehensive book, Iain McGilchrist details the differences between the hemispheres of humans. As he suggests, the hemispheres make individually coherent but incompatible representations of the external world and are in tension with each other. McGilchrist says the left hemisphere is focused and abstracting. It understands explicit information and deals with it in discrete packages.… is disengaged from context, and consequently, carries out its functions impersonally and without empathy. By contrast, the right hemisphere deals with implicit information and the whole picture in context….with the individuals concept of self in context and realistically, as opposed to the left hemisphere’s predilection to self-aggrandizement and confabulation. The right hemisphere is given to understanding others and so to have empathy and be cooperative. As found in many species, the right hemisphere of humans responds to new events and stimuli, which would also be as aspect of its ability to relate to objects and events in context. (166-167)

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