Academic journal article Cosmos and History: The Journal of Natural and Social Philosophy

Consciousness Began with a Hunter's Plan

Academic journal article Cosmos and History: The Journal of Natural and Social Philosophy

Consciousness Began with a Hunter's Plan

Article excerpt

WHERE IS CONSCIOUSNESS FOUND?

My first premise is that only firm evidence for the existence of consciousness in any being other than one's self cones by inference from observing goal-directed behaviors and participating in cooperative or destructive relationships: hunt and be hunted. All else is speculation.

My second premise is that primitive conscious beings emerged in the Cambrian Sea half a billion years ago in multiple forms. They engaged in Darwinian competition of eat or be eaten and thereby evolved increasing complexity. William James postulated that the advance took the form of "... an organ added for the sake of steering a nervous system grown too complex to regulate itself." [James 1879, p. 18]. Thee necessary though not sufficient condition for emergence was growth in the sizes of the brains and bodies that are exemplified by the sizes of organisms with which today we car engage on terms of accessibility. Some 200 million years later the first vertebrates emerged with a significant concentration of neurons in the primordial forebrain (Figure 1) consisting of the two hemispheres enclosed in a helmet-like skull. The anterior third of each hemisphere was sensory (predominantly olfactory), the lateral third was motor (mainly for the jaws), and the medial third was for navigation (the primitive hippocampal formation).

At the center of each hemisphere was a small transitional area labeled "TA" by Herrick [1948], which received input from other sensory systems (vision, audition and body). As brains evolved, this area greatly expanded while preserving the close functional connections with each other in a ring along the edge of each hemisphere, which has been retained as the limbic system. The organization of the brain makes sense only when it is seen as having been shaped by the requirements for phylogenetic and embryological unfolding. From this perspective the topological center of the forebrain is not the thalamus but the entorhinal cortex, which was the first six-layered neocortex to emerge at "TA" from the three-layered primitive allocortex. Neocortex with its potential for avast surface area expanded the arms race and the importance of consciousness as the weapon of choice.

My third premise is that the "organ" added by evolution was neuropil, which is a sheet of neurons and neuroglia that are densely packed and interconnected by innumerable channels conducting chemical and electrical fields of energy, and by specific mechanisms of engagement of neurons in dyadic pairs through synapses. The tissue contains the cell bodies of the neurons and neuroglia and a capacious capillary network that brings oxygen and nutrients and removes carbon dioxide, heat, and other waste products from the extremely high rates of metabolism. The neurons typically form layers and palisades with dendrites aligned perpendicularly to the sheets called laminated neuropil, which is better known in vertebrate brains as cerebral cortex.

Neuropil is found in all vertebrates and in the more behaviorally sophisticated invertebrates, such as cuttlefish among mollusks and bees among arthropods. Interactions are en masse, owing to the extreme packing density of the cells and their dendrites and axons. The dynamics must be described by use of continuous variables in space, time and energy in differential equations or equivalent [Freeman 1975]. Neuropil embeds neural networks with discrete synaptic dyads. Two levels of function are required. At the microscopic level the dynamics of neurons and synapses is observed by recording action potentials of small representative sample of cell bodies and axons. At the macroscopic level the dynamics or neural populations is observed by recording EEG waves generated by hundreds of millions of neurons. I postulate that the dense activity of neuropil expressed in continuous macroscopic images is required by brains in order to construct and express the memories that humans experience in their customary richness of detail. …

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