Primary Consciousness - Theories

Theories

One prominent theory for the neurophysiological basis of primary consciousness was proposed by Gerald Edelman. This theory of consciousness is premised upon three major assumptions:

1. The laws of physics apply to consciousness, which rules out concepts such as spirits and a soul and allows for a purely physiological model of consciousness.
2. Consciousness is an evolved characteristic, which means it is a helpful characteristic from a Darwinian perspective.
3. There is no such thing as a "qualia-free" observer. Qualia are collections of personal or subjective experiences, feelings, and sensations that inevitably come with human awareness.

Edelman's theory focuses on two nervous system organizations: the brainstem and limbic systems on one side and the thalamus and cerebral cortex on the other side. The brain stem and limbic system take care of essential body functioning and survival, while the thalamocortical system receives signals from sensory receptors and sends out signals to voluntary muscles such as those of the arms and legs. The theory asserts that the connection of these two systems during evolution helped animals learn adaptive behaviors. This connection allows past signals related to values set by the limbic-brain stem system and categorized signals from the outside world to be correlated, resulting in memory in conceptual areas. This memory is then linked to the organism's current perception, which results in an awareness of the present, or primary consciousness. In other words, Edelman posits that primary consciousness arises from the correlation of conceptual memory to a set of ongoing perceptual categorizations—a "remembered present".

Other scientists have argued against Edelman's theory, instead suggesting that primary consciousness might have emerged with the basic vegetative systems of the brain. That is, the evolutionary origin might have come from sensations and primal emotions arising from sensors and receptors, both internal and surface, signaling that the well-being of the creature was immediately threatened—for example, hunger for air, thirst, hunger, pain, and extreme temperature change. This is based on neurological data showing the thalamic, hippocampal, orbitofrontal, insula, and midbrain sites are the key to consciousness of thirst.

These scientists also point out that the cortex might not be as important to primary consciousness as some neuroscientists have believed. Evidence of this lies in the fact that studies show that systematically disabling parts of the cortex in animals does not remove consciousness. Another study found that children born without a cortex are conscious. Instead of cortical mechanisms, these scientists emphasize brainstem mechanisms as essential to consciousness. Still, these scientists concede that higher order consciousness does involve the cortex and complex communication between different areas of the brain.