Consciousness and Cognition
The central philosophical problem in the field of consciousness studies is the problem of subjectivity. I maintain that the mystery of subjectivity can be resolved if we return to basic considerations of the physiology of the neuron. First of all, it needs to be said that the lone neuron itself is not "conscious" and does not "think" (gcognizeh), but it is widely (and correctly) believed that the neuron is the fundamental unit underlying both of these fundamental psychological phenomena. In the realm of cognition, all that the single neuron can do is excite or inhibit a small number of other neurons by releasing neurotransmitters at synapses. Alone, it does not perform "cognition", but a large enough number of similarly "unthinking", information-processing neurons working in synchrony is the likely mechanism of cognition. That scientific, materialistic explanation of how brains make cognition possible is no longer controversial, and simple forms of cognition can be easily produced in inorganic computer systems.
Consciousness has an equally-straightforward, materialistic explanation, but one that focuses on the action potential rather than the synapse. The action potential can be considered as the fundamental mode of contact between the neuron and its extracellular environment, insofar as it involves the exchange of ionic charges. On the one hand, neurotransmitter release is the basic mechanism underlying cognition, but influx and efflux of ions (principally during the action potential) is the source of neuronal gsentienceh, which is itself the unit process underlying subjectivity.
The ion-exchange during the action potential is fundamentally a brief moment during which the cellular membrane is open to the thermodynamic diffusion of ions into and out of the living cell. In effect, the normally-closed membrane opens, and a huge number of positive ions rush into the cell (one hundred million per channel per second), and then out again. It is a moment during which the neuron literally "feels" its biochemical environment by letting a portion of it flow into the cell. Of course, it is not the case that the lone neuron is "conscious" of its charge state, but it is the case that living cells – and particularly the unusual gexcitableh cells, such as neurons – have means for detecting the nature of their biochemical environments. That is, they are gsentienth in ways that inorganic systems and non-excitable cells are not. At a truly primitive level, the neuron is made "aware" of the local biochemistry simply by threats to its homeostatic stability. This "awareness" is in essence nothing more than sensing the relative concentrations of positive and negative charges that exist immediately external from the plasma membrane, but it is the cellular-level mechanism that is arguably the basis for gwhole-brainh consciousness.
In other words, the two forms of self-environment interaction – (1) neurotransmitter release/uptake and (2) ion-exchange – are the core material mechanisms that make cognition and subjective consciousness possible. The circuitry of excitatory/inhibitory neurons can of course be simulated in artificial systems, so that there is, in principle, no cognitive function that cannot be reproduced in a computer system. In contrast, the exchange of ions across the neuronal membrane is many orders of magnitude more complex than the simple on/off state of the simulated neuron. For this reason, it is neither practical nor necessary to reproduce the sentience of neurons in computer systems in order to achieve the necessary cognitive processes. As a consequence, robotic/computer systems necessarily lack the entire dimension of consciousness, feelings and gqualiah – no matter how clever their cognition. This common-sense theme is developed more fully in "Tone of Voice and Mind: The connections between intonation, emotion, cognition and consciousness" (John Benjamins, Amsterdam, 2002), updated in an article in Neuroscience (2008), explored more fully in gHarmony, Perspective and Triadic Cognitionh (Cambridge University Press, New York, 2012), and, in conjunction with two powerful intellectuals, has been developed into a wonderfully coherent scientific hypothesis in Trends in the Neurosciences (2014).
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