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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

Della Chiesa, Andrea, et al. Multiple Landmarks, the Encoding of Environmental Geometry and the Spatial Logics of a Dual Brain. Animal Cognition. 9/4, 2006. The lead author is at the Laboratory of Animal Cognition and Comparative Neuroscience, chaired by Giorgio Vallortigara, at the University of Trieste. A characteristic attribution of fine focus to the LH and spatial context to the RH is indeed found to persist across the Metazoa, in this case the avian kingdom.

Under conditions of monocular vision, chicks tended to rely on different strategies to localize the centre on the basis of the eye (and thus the hemisphere) in use, the left hemisphere attending to details of the environment and the right hemisphere attending to the global shape. (281)

Duboc, Veronique, et al. Asymmetry of the Brain: Development and Implications. Annual Review of Genetics. 49/647, 2015. In these mid 2010s when many research projects over past decades are reaching successful confirmations, University of Toulouse neuroscientists gather and review some 170 references that explain how bilateral brain hemispheres distinguish every vertebrate and invertebrate phylum. An elaborative constancy is thus revealed from life’s earliest rudiments through to primates and human beings. Moreover the same left half finer detail, and right side whole field, a vital reciprocity of item and emotion, is maintained for every species. As Earth’s evolutionary emergence now transitions to a worldwise humanity, one wonders where the consequent bicameral hemispheres, along with a corpus callosum, might be. Our Complementarity of Civilizations section proceeds to document just such an east/west, south/north, Islamic presence.

Although the left and right hemispheres of our brains develop with a high degree of symmetry at both the anatomical and functional levels, it has become clear that subtle structural differences exist between the two sides and that each is dominant in processing specific cognitive tasks. As the result of evolutionary conservation or convergence, lateralization of the brain is found in both vertebrates and invertebrates, suggesting that it provides significant fitness for animal life. (Abstract Excerpt)

Brain Asymmetry is Widespread in Animals: LR asymmetry is a general feature of animal brains, and a variety of functional and anatomical asymmetries have been described in both vertebrates and invertebrates. As in humans, for instance, all primates investigated so far show an asymmetry in their facial expression while communicating an emotion—i.e., a stronger emotion on the left side of their face — suggesting that right hemisphere dominance for processing of emotions probably predates the human-monkey split. Meanwhile, the left hemisphere has been implicated in the generation or perception of vocalizations in primates and mice, suggesting a conserved role of this hemisphere in communication. Interestingly, in both mammals and insects, brain lateralization has been associated with learning and the retrieval of short- versus long-term memory. For instance, the vast majority of Drosophila that possess an asymmetric body (AB), a small nucleus inside the brain that is usually only found in the right hemisphere, display more efficient long-term memory than those with a bilateral AB. In honeybees, recall of short-term memory is favored if odors are presented to the right antenna, whereas the reverse is true for long-term memory. (649-650)

Falk, Dean. Brain Evolution in Females. Lori Hager, ed. Women in Human Evolution. New York: Routledge, 1997. Males on average have larger left hemispheres, while females have a brain lateralization that favors the right side along with more corpus callosum interconnections in between.

Forrester, Gillian, et al, eds. Cerebral Lateralization and Cognition: Evolutionary and Developmental Investigations of Behavioral Biases. Progress in Brain Research. Volume 238, 2018. This is a copious collection which proceeds to show how widespread and important bicameral brain asymmetries are across every animal grouping. Most prominent in human beings, an ancient, axial encephalization traced to insect invertebrates consistently makes use of reciprocal detail and image faculties as the best way to survive and evolve. Among the 15 papers are Insights into the Evolution of lateralization from the Insects, Motor Asymmetries in Fishes, Amphibians, and Reptiles, Mother and Offspring Lateralized Social Behavior, and Sensorimotor Lateralization Scaffolds Cognitive Specialization.

Frasnelli, Elisa, et al. Left-Right Asymmetries of Behaviour and Nervous System in Invertebrates. Neuroscience & Biobehavioral Reviews. 36/4, 2013. In a paper that accords with the 2013 volume Divided Brains (search Rogers), Elisa Frasnelli, Konrad Lorenz Institute for Evolution and Cognition Research, Giorgio Vallortigara, University of Trento, and Lesley Rogers, University of New England, NSW, find that even in these rudimentary creatures, mostly unchanged from the Cambrian era, the same left detail and right field cerebral complements are similarly present. By a comparison with the 2013 PNAS Supplement: “In the Light of Evolution VII,” (search Cela-Conde) from our late humankind vista, a singular archetypal brain appears to evolve and develop as if relative embryonic maturation.

Evidence of left–right asymmetries in invertebrates has begun to emerge, suggesting that lateralization of the nervous system may be a feature of simpler brains as well as more complex ones. A variety of studies have revealed sensory and motor asymmetries in behaviour, as well as asymmetries in the nervous system, in invertebrates. Asymmetries in behaviour are apparent in olfaction (antennal asymmetries) and in vision (preferential use of the left or right visual hemifield during activities such as foraging or escape from predators) in animals as different as bees, fruitflies, cockroaches, octopuses, locusts, ants, spiders, crabs, snails, water bugs and cuttlefish. Asymmetries of the nervous system include lateralized position of specific brain structures (e.g., in fruitflies and snails) and of specific neurons (e.g., in nematodes). As in vertebrates, lateralization can occur both at the individual and at the population-level in invertebrates. Theoretical models have been developed supporting the hypothesis that the alignment of the direction of behavioural and brain asymmetries at the population-level could have arisen as a result of social selective pressures, when individually asymmetrical organisms had to coordinate with each other. The evidence reviewed suggests that lateralization at the population-level may be more likely to occur in social species among invertebrates, as well as vertebrates. (Abstract)

Ghirlanda, Stefano and Giorgio Vallortigara. The Evolution of Brain Lateralization. Proceeedings of the Royal Society London B. 271/853, 2004. A game-theoretic analysis of population structures shows that cerebral asymmetry is favored in animal assemblies, which results in a left side bias for categorizing objects and stimuli and a right hemisphere better at spatial orientations. These attributes are seen to hold across many taxa from fishes to mammals.

Giljov, Andrey, et al. Facing Each Other: Mammal Mothers and Infants Prefer the Position Favouring Right Hemisphere Processing. Biology Letters. 14/1, 2018. St. Peterburg State University zoologists Giljov, Karina Karenina, and Yegor Malashichev provide still another view upon a maternal nature which begins and nurtures life by way of an emphatic, relational, right brain visual interaction.

The right hemisphere plays a crucial role in social processing. Human mothers show a robust left cradling/holding bias providing greater right-hemispheric involvement in the exchange of social information between mother and infant. Here, we demonstrate that a similar bias is evident in face-to-face spatial interactions in marine and terrestrial non-primate mammals. Walruses and Indian flying foxes showed a significant population-level preference for the position which facilitates the use of the left visual field in both mother and infant. This behavioural lateralization may have emerged owing to benefits conferred by the enhanced right-hemispheric social processing providing the mother and infant an optimal perception of each other. (Abstract)

Godfrey-Smith, Peter. Integration, Lateralization, and Animal Experience. Mind & Language. 36/2, 2021. The University of Sydney biophilosopher adds a latest note about the widely pervasive presence of bicameral cognitive faculties across every manner and range of life’s evolving fauna and flora.

Many vertebrate animals approximate, to various degrees, the “split‐brain” condition that results from surgery done in humans to treat severe epilepsy, with very limited connection between the left and right sides of the upper parts of the brain. The split‐brain condition has been the topic of extensive philosophical discussion, because it appears, in some circumstances, to give rise to two minds within one body. Is the same true of these animals? This article attempts to make progress on two difficult topics—animal experience, and the consequences of the human split‐brain condition—by considering both at once. (Abstract)

Gunturkun, Onur. Brain Asymmetry in Vertebrates. Lazareva, Olga, et al, eds. How Animals See the World: Comparative Behavior, Biology, and the Evolution of Vision. Oxford: Oxford University Press, 2012. Scientific realizations that complementary bilateral brains occur across Metazoan creatures and deep into evolutionary lineages have just dawned for the past decade or so. In this chapter, a Ruhr-University Bochum biopsychologist claims that such left/right, local/global, detail/context hemispheric proclivities are now proven to persist throughout primate, mammalian, avian, and amphibian kingdoms. Thus for us another significant presence of these gender archetypes is granted, just as genomics now affirms a reciprocity of nucleotide and network. See also Gunturkun’s “Hemispheric Asymmetries” in Frontiers in Psychology (3/5, 2012) and “The Convergent Evolution of Neural Substrates for Cognition” in Psychological Research (76/1, 2012).

As will be shown, left-right differences of brain and function are not only widespread among mammals, but also among many other vertebrates. Thus, cerebral asymmetry is a ubiquitous phenomenon that possible is not the exception, but the rule, Brain asymmetries deeply affect the neural processes of vision at all levels of analysis. This chapter therefore attempts to review animal asymmetries of handedness and vocalization, as well as visual asymmetries of features and space. In this chapter, it will become clear that in all three reviewed areas of asymmetry research, the observations follow a largely consistent pattern. (504)

Since the landmark study of (David, 1977) Navon, many studies with human subjects have confirmed the existence of a functional asymmetry with a local bias for the left and a global bias for the right hemisphere. These studies revealed that, for example, the left hemisphere excels in identifying local features, whereas the right hemisphere is usually faster and more accurate in identifying global components of the input. Thus, cerebral asymmetries that favor a left hemispheric strategy for attending to local features and a right hemispheric bias to use global and possibly relational spatial cues is firmly founded in studies with human subjects. This cognitive asymmetry is to some extent shared by mammals and birds; it might have a long phylogenetic history. (505)

If a pattern is initially learned, then the object’s parts and their spatial relationships have to be encoded separately before creating a stored structural description. This process is dominated by the left hemisphere, which is especially suited to analyzing local stimulus details. However, once this form has become familiar, its global shape can be directly matched to information stored in memory be configurational analyses. This global shape discrimination process is primarily guided by right hemisphere structures which are specialized in global stimulus analysis. (505)

Several conclusions follow from the above discussion. First, not only humans, but also nonhumans animals have asymmetries of brain and behavior at the population level. This fact has been documented in some 1,000 scientific publications that were conducted with more than 50 different species. Second, most of these asymmetries show a rather consistent pattern, especially for communication. This pattern is also to some extent true for handedness and visual analysis of features and space. All of this evidence clearly points to a common heritage of cerebral asymmetries. We, as a species, have inherited these left-right differences and have then developed our own species-typical mechanisms of vision, language, manual control, onto this asymmetrical fundament. (513)

Gunturkun, Onur and Sebastian Ocklenburg. Ontogenesis of Lateralization. Neuron. 94/2, 2017. Largely unknown a decade or more ago, Ruhr-University Bochum, Germany and Sellenbosch University, South Africa biopsychologists here affirm that “a general principle of nature” seems to be life’s proclivity from an evolutionary outset to form beneficial asymmetric neural divisions. Across animal kingdoms from invertebrates and fish to fowl, mammals, primates, and especially ourselves, a part/whole reciprocity serves development and survival. May we then muse that a similar “Phylogenesis” could be equally in effect?

The brains of humans and other animals are asymmetrically organized, but we still know little about the ontogenetic and neural fundaments of lateralizations. Here, we review the current state of understanding about the role of genetic and non-genetic factors for the development of neural and behavioral asymmetries in vertebrates. At the genetic level, the Nodal signaling cascade is of central importance, but several other genetic pathways have been discovered to also shape the lateralized embryonic brain. Studies in humans identified several relevant genes with mostly small effect sizes but also highlight the extreme importance of non-genetic factors for asymmetry development. This is also visible in visual asymmetry in birds, in which genes only affect embryonic body position, while the resulting left-right difference of visual stimulation shapes visual pathways in a lateralized way. These and further studies in zebrafish and humans highlight that the many routes from genes to asymmetries of function run through left-right differences of neural pathways. (Abstract)

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)

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