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

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

Gunturkun, Onur and Sebastian Ocklenburg. The Lateralized Brain: The Neuroscience and Evolution of Hemispheric Asymmetries. Cambridge, MA: Academic Press, 2017. Ruhr-University Bochum, Germany neuroscientists provide a latest survey of 21st century findings about a complementary neural faculty which graces every creature from ourselves all the way to rudimentary invertebrates. Chapters range from Brain Asymmetries: Two Millennia of Speculation, Research and Discoveries to The Role of the Corpus Callosum, Spatial Attention, Self Perception and the Right Hemisphere, and Sex Differences. See also Ontogenesis of Lateraliztion by the authors in Neuron. 94/2, 2017.

Gunturkun, Onur, et al.. Brain Lateralization: A Comparative Perspective. Physiological Reviews. 100/1019, 2020. Ruhr University Bochum neuroscientists (search OG) provide a latest comprehensive review of what portends to be a visionary 2020s discovery. From 20th century rudiments, it is now well proven, as this section attests, that common cognitive and behavioral attributes can be similarly traced in kind across life’s Metazoa to the earliest invertebrate neural systems. (Every creature has a hemi.) Again the same left detail and right image reciprocity holds everywhere. A common example is a bird that pecks with one eye and scans the sky with the other. With over 500 references, a bicameral universality is well confirmed so as to reveal the ultimately bigender triality of an ecosmic reproductive genesis.

Comparative studies on brain asymmetry date back to the 19th century but then waned because brain lateralization was seen as uniquely human. But since the 1970s and 1980s, we have learned that left-right differences of brain and behavior exist throughout the animal kingdom for sensory, cognitive, and motor efficiency benefits. As outlined in our review, novel animal models and approaches could be established in the last decades, and they already produced a substantial increase of knowledge. Since there is practically no realm of human perception, cognition, emotion, or action that is not affected by our lateralized neural organization, insights from these comparative studies are crucial to understand the functions and pathologies of our asymmetric brain. (Abstract excerpt)

E. Evolutionary Advantages of Hemispheric Asymmetries: Third, if two complementary neural processes are computed in parallel in the two hemispheres, cognitive redundancy is reduced and overall efficacy is increased. Indeed, when lateralized and nonlateralized chicks perform a task in which they have to quickly search for grains scattered among pebbles and in parallel monitor birds of prey that occasionally fly overhead, the lateralized individuals perform both tasks at a higher level. (1026)

In the second section of this review, we will use the examples of the zebrafish, the pigeon, and the nematode C. elegans to discuss the question of how brain asymmetries
emerge during ontogenesis. In the third section, we will highlight different perceptual and motor asymmetries using mostly studies on bird species as examples. The fourth section deals with asymmetrical organized networks in the brain, with humans and pigeons as prime examples. In the fifth and last section, we will focus on language lateralization and lateralization in emotional processing based on studies on humans, songbirds, and non-human primates. (1027)

Although the left hemisphere shows a dominance for processing language, the right hemisphere contributes specific aspects to language (e.g., prosody). This difference is likely based on a general left hemispheric advantage to process temporal and a right hemispheric
advantage to process structural features. (1050)

Hahner, Linus and Andreas Nieder. Volitional spatial attention is lateralized in crows. Proceedings of the Royal Society B. January, 2024. University of Tübingen neurobiologists add a further distinction to the common bicameral faculties which extend throughout creaturely species. While the right eye to left hemisphere views fine detail (seeds, words), herein it is reported that as left field crosses to the right brain it achieve an integral survey (sky predator) and behavioral responses.

Like humans and other animal species, birds exhibit left–right asymmetries due to hemispheric functions. However, the potential lateralization of executive control remains unknown. Here, we demonstrate that crows exhibit more pronounced attention for stimuli viewed in the left visual hemifield. In tests we found that cued targets were detected more efficiently in the left view compared with the right visual field. These findings ikply that crows, like humans, exhibit superior executive control of attention in the left-eye/right hemisphere system of their brains. (Abstract)

Since both crows and humans show left-eye-system superiority for executive control, it leads us to speculate that right-hemispheric dominance for controlling visuospatial functions might be phylogenetically conserved across species.

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)

Lapraz, Francois, et al. Brain bilateral asymmetry – insights from nematodes, zebrafish, and Drosophila. Trends in Neuroscience. 47/10, 2024. This October paper by Université Côté d'Azur, CNRS, France biopsychologists including Stéphane Noselli is a good example of mid 2020s abilities to ascertain and wholly fill in what nature seems to avail as a premier cognitive attribute. In regard, this asymmetrical facility with two dedicated functions has been known since the 1970s as the human hemispheres. Into the 21st century, the presence of this vital reciprocity has been identified across all Metazoan creatures from vertebrate primates all the way its quantified occurrence in invertebrate worms and insects, as this work attests. Thus after some 50 years this local to global neurobiology research project approaches an historic conclusion. As such, life’s entire, fittest, complementary intelligent edification could be well appreciated as truly in evidential existence on its phenomenal own.

The nervous system in bilaterian organisms displays a lateralized organization by way of asymmetrical neuronal circuits and brain functions. Although body asymmetry is understood, the asymmetry of the nervous system displays greater phenotypic, genetic, and evolutionary variability. In this review we explore the use of nematode, zebrafish, and Drosophila genetic models to investigate neuronal circuit asymmetry. We discuss recent discoveries in the context of body–brain concordance and highlight the distinct characteristics of nervous system asymmetry and its cognitive correlates.

To our knowledge, Drosophila H-neurons represent the only known arthropod directional asymmetrical circuit. Although many arthropod species exhibit lateralized behaviors, such as leg response in locusts, or asymmetrical contributions of hemispheres and cognitive functions in ants and bees, the neuronal substrates underlying these asymmetries remain to be fully elucidated. (11) The discovery that the lateralized activity of the Netrin pathway is crucial for H-neuron laterality in flies suggests a mechanism for circuit asymmetry in which a patterning dimension is added to a classical guidance pathway. (12)

Emergence of Asymmetry from an initially symmetrical state is a universal transition in Nature. Living organisms show striking asymmetries at all scales (molecular, cellular, tissular, organismal) and one of their fundamental features lies in their assembly from homochiral molecular components. Whether the macroscopic asymmetries of living systems are directly related to their molecular chirality remains an open question. We study Left-Right Asymmetry in Drosophila to characterize the molecular basis of laterality and address the origin, propagation and evolution of symmetry breaking. (Noselli website)

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)
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