Human Consciousness: stimuli, analog to digital (Humans)

by David Turell , Sunday, September 11, 2016, 15:44 (2777 days ago) @ David Turell

A philosopher's thoughts with an emphasis on the cellular level:-http://nautil.us/blog/consciousness-is-made-of-atoms-too-"science has not been able to show how mind or human consciousness can be incorporated into [ our scientific understanding]. ...neurobiology has made some progress as to how perception and thought actually take form. Consciousness may well be made of atoms, and it all begins with sensations. -"It is clear that neural systems evolved to enable animals to move in their environments—to find food and mates, and to avoid or otherwise deal with predators. Stimuli are received from the environment, assembled by central neural circuits, and transmitted to muscles or other tissues in the animals' bodies whose coordinated activity enable it to respond. This process occurs in every complex multi-celled animal.-"The first step is the conversion of stimuli from the environment into sensations. Since animals are composed entirely of cells, this process must occur at the cellular level—that is, stimuli from the environment activate receptor cells on the surface or within their bodies. These stimuli are of three types: electromagnetic radiation in the range of wavelengths we identify as light, pressures from objects or the air striking the body, and streams of molecules in the air or in direct contact with the animals' bodies. A variety of receptor cells exist to receive and record these stimuli.-"In every case, these environmental stimuli exist in analog form and are converted into digital form by the receptor cells and the neural circuits connected to them. For example, the “eye” of the horseshoe crab Limulus can create a boundary line within a gradient of light from light to dark. That boundary gives the animal something to respond to within the analog stream of radiation. In the human eye, color pigments (carotinoids) in the retina are able to absorb small portions of the electromagnetic spectrum to create the colors we identify and respond to. (my bold) -"The same is true of the other sensory modalities. Specialized receptor cells in the skin, the ear, on the tongue and in the nasal passages respond to selected portions of the swarms of molecules and pressure changes in the environment. All are conversions of analog stimuli into digital form. -***-" Sensations are the building blocks of consciousness. They must first be combined into perceptions and converted into objects in the environment. Then neural systems must evolve mechanisms by which they can be remembered or recalled; and finally plasticity must develop—the capacity to shape, edit, and organize this neural content, present or remembered, into a picture, experience, or awareness of the “world.” This is the way consciousness emerges in neural systems.-"In 1934, the Estonian biologist Jakob von Uexküll published a monograph titled, A Stroll Through the Worlds of Animals and Men (intriguingly subtitled A Picture Book of Invisible Worlds) in which he attempted to show that every animal creates a “world” (he called it its umwelt) from stimuli in the environment to which it responds. Even an animal such as the common wood tick, with which he begins his essay, creates such a world. The wood tick responds to only three stimuli: butyric acid (which is secreted by the skin glands of mammals), which causes the tick to drop onto it from its perch; the shock of landing on its victim, which causes it to scramble among its hairs; and the warmth of the animal's skin, which causes it to bore into it for its meal of blood. -"These three stimuli alone create an umwelt for the tick, “impoverished” as it may be. We can add to his account only that the three stimuli—butyric acid, the shock of landing, and the warmth of the animal's skin—are analog stimuli, that is, they are undifferentiated gradients in the environment from which the neural system of the tick selects just portions for its response. Those portions, converted into digital form, are the sensations that constitute its tiny world.-"There is nothing “mental” or “physical” in this account of sensations. That distinction makes sense only much further down the line in the evolution of neural systems and requires the development of memory and neural plasticity along with a far richer sensory world than the wood tick's. Sensations are the creation within neural systems of environmental events cast in different form, but still part of the same single material fabric of the universe. They reside in the animal's central neural system—its brain (as MRI studies reveal)—and can be given a general location for where they occur."-Comment: Stimuli are one aspect of developing consciousness. He certainly doesn't give us a full explanation of consciousness. My bolded section is to point out the automaticity of cell response to stimuli he is suggesting. His essay also shows how the physics of biology is important.