VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies
3. An Emergent Bicameral Brain
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)
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. 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)
Vauclair, Jacques, et al. The Study of Hemispheric Specialization for Categorical and Coordinate Spatial Relations in Animals. Neuropsychologia. 44/1524, 2006. This extensive article sorts out several prior studies of brain hemisphere attributes in mammals and birds to arrive at a general correlation of fine focus, particular attention with the left side and a broader, more holistic survey with the right brain. As a result, these qualities or functions, most pronounced in humans, are found to have a long evolutionary heritage. Not quantified a decade ago, here is still another novel indicator of a universal creative complementarity.
The left hemisphere seems to focus on smaller portions of a pattern, does not care of the configuration of these portions, and is rather effective in acquiring a category that can be transferred to novel pictures. Contrary, the right hemisphere is more globally driven, uses relational information and is less effective in transferring to new exemplars. (1530) Typically, the RH is faster and more accurate to identify global components of the input and the LH is faster and more accurate to identify local components. (1531) ….a local- versus global distinction that results from left- and right-hemispheric mechanisms, respectively, can be found in nonhuman primates and pigeons. (1531) Thus, an asymmetric local/global distinction could be a very old feature of vertebrate brains. (1531)
Yamazaki, Y, et al. Lateralized Cognition: Asymmetrical and Complementary Strategies of Pigeons. Cognition. 104/2, 2007. Over the last decade researchers have quantified that our human brain bicameral attributes of a left particulate focus and right integral context, now agreed upon, similarly occur across the animal kingdoms. This subject article explains how pigeons discriminate and observe their environment in such like manner. Now from this vantage, a salient discovery ought to be noted. A cerebral complementarity is found to distinguish and emerge with creaturely evolution, coming to full capacity in reflective persons. This achievement further reveals the manifest presence of a universal archetypal reciprocity.
The results suggest that the left hemisphere employs a category strategy and concentrates on local features, while the right hemisphere uses an exemplary strategy and relies on configuration. These cognitive dichotomies of the cerebral hemispheres are largely shared by humans, suggesting that lateralized cognitive systems already defined the neural architecture of the common ancestor of birds and mammals. (315-316) On the basis of these findings, it is likely that the RE/LH (right eye) analyzes objects in detail, whereas the LE/RH attends to broader parts of the stimuli as well as to their configuration. (318)