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

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

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.

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)

Schnell, Alexandra, et al. Lateralization of Eye Use in Cuttlefish: Opposite Direction for Anti-Predatory and Predatory Behaviors. Frontiers in Physiology. December, 2016. Normandie University, Caen and Woods Hole Marine Biological Laboratory researchers find the same cross-hemisphere referral of left finer focus and right wide view in this Cephalopoda class as human beings do. Again these common, bicameral modes are found to hold across every animal realm. (Their unified reciprocity could well serve as a natural model for bipartisan politics.)

Vertebrates with laterally placed eyes typically exhibit preferential eye use for ecological activities such as scanning for predators or prey. Processing visual information predominately through the left or right visual field has been associated with specialized function of the left and right brain. Lateralized vertebrates often share a general pattern of lateralized brain function at the population level, whereby the left hemisphere controls routine behaviors and the right hemisphere controls emergency responses. (Abstract excerpt)

Tommasi, Luca. Mechanisms and Functions of Brain and Behavioural Asymmetries. Philosophical Transactions of the Royal Society B. 364/855, 2009. An introduction to this dedicated issue whose papers could represent a synthesis of research areas not possible earlier. For some years the study of brain hemisphere attributes with regard to humans or non-humans proceeded somewhat on their own. Sufficient findings are now in place to join a deep evolutionary continuity with the generic propensities of the left side for close detail, and the right side for integral image. A synoptic contribution by Michael Corballis is noted above.

Asymmetries in behavior exhibited by birds, fishes, amphibians, rodents and primates have since provided a strong argument for functional lateralization being a universal and evolutionarily ancient trait of the vertebrate brain. (856)

Vallortigara, Giorgio and Lesley Rogers. A Function for the Bicameral Mind. Cortex. Online December, 2019. The University of Trento, Italy and University of New England, Australia senior scholars continue to advance understandings of the pervasive presence and advantages across all phyla of dual brain hemispheres with opposite but complementary discrete particle (seed, me) or whole image (relations, We) attributes. This deep evolutionary benefit is most manifest in human cerebral activity, but we seem to work against this reciprocity as evident by local and global political conflicts. (Here is an example of a worldwide scientific discovery about a vital neural anatomy across animal kingdoms which a male (dots only) academia is unable to comprehend.)

A lateralized brain, in which each hemisphere processes sensory inputs and carries them out in different ways, is common in vertebrates, and it now reported for invertebrates too. As shown in many animal species, having a lateralized brain can enhance the capacity to perform two tasks at the same time. Why is this the case? Not only humans, but also most non-human animals, show a similar pattern of directional asymmetry. For instance, from fish to mammals most individuals react faster when a predator approaches from their left side. Using mathematical theory of games, it has been argued that the population structure of lateralization may result from the type of interactions asymmetric organisms face with each other. (Abstract excerpt)

Vallortigara, Giorgio and Lesley Rogers. Survival with an Asymmetrical Brain: Advantages and Disadvantages of Cerebral Lateralization. Behavioral and Brain Sciences. 28/4, 2005. Over the past decade, many studies have quantified that a bilateral brain with complementary hemispheric functions, once thought to be uniquely human, is present throughout the animal kingdom. On an evolutionary scale, this archetypal anatomy can be traced from primates to birds, rodents, reptiles, amphibians and fish. In general, the left brain is associated with the right visual field, and vice versa. This article notes a liability for creatures if predators approach from a side whose hemisphere is less apt in their notice. But as a whole, with a typical left brain for fine local discrimination (seeds among pebbles) and the right for spatial perception and emotions, it is of advantage to have this division of cognitive effort.

Vallortigara, Giorgio, et al. Separate Geometric and Non-Geometric Modules for Spatial Reorientation. Journal of Cognitive Neuroscience. 16/3, 2004. From the Universities of Trieste and Padua, a contribution that asymmetrical, hemispheric cerebral faculties can be found amongst primates, mammals, birds, amphibians, and fish. In this case, studies of the chicken avian brain typically find a characteristic left side penchant for detail with a right half attention to contextual wholes. Metazoan evolution then seems to proceed by the merger of initially separate modules toward a manifest integral synthesis in humans.

The results suggest separate mechanisms for dealing with spatial reorientation problems, with the right hemisphere taking charge of large-scale geometry of the environment and with both hemispheres taking charge of local, non-geometric cues when available in isolation, but with a predominance of the left hemisphere when competition between geometric and non-geometric information occurs. (390)

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