Consciousness - Part 1 - Part 2

Consciousness is usually defined as the part of the human mind that is aware of the feeling, thoughts and surroundings. Actually there is no simple, agreed-upon definition of consciousness. A more detailed definition(s) will be discussed later. Most of the philosophical discussions of consciousness arose from the mind-body issues posed by Rene' Descartes in the 17th century. He asked: Is the mind, or consciousness, independent of matter? Is consciousness physical or non-physical? It is now recognized that the phenomena by which we define consciousness are correlated with certain configurations of activity in certain nervous systems and not with others. Most neural activity doesn't generate consciousness, even in the supremely conscious human brain. Moreover, the activities that do generate consciousness do not produce it by accident or in a happenstance manner. Consciously processed events in the nervous system have a very clear physical signature, in the form of characteristic brain activity.

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There is good empirical evidence that consciously registered events leave distinct traces in the brain and are processed in special ways within the brain's networks. Techniques such as EEG, MRI, and PET provide information about the relationship between mental tasks and the collective activities of groups of many millions of neurons. In stark contrast to this, electrodes have been developed which are so fine that their tips can be inserted into single cells so that the firings of individual neurons in some brain location can be monitored. It is possible to see how an individual neuron reacts when an animal is looking at an object moving sideways, or seeing the colour blue, or planning an action.

Sigmund Freud, the founder of psychoanalysis, compared the human mind to an iceberg. The tip above the water represents consciousness, and the vast region below the surface symbolizes the unconscious mind. This subconscious mind is the sum total of our past experiences. What we feel, think, or do forms the basis of our experience. These experiences are stored in the form of subtle impressions in our subconscious mind. These impressions interact with one another and create tendencies. The resultant of these tendencies determines our character. However, if the unconscious drives (the id) might prompt behavior that would be incompatible with our civilized conception of ourselves, the action would be suppressed by the conscious mind (the ego). This Freudian concept has been fallen out of favor by 1950s. Better understanding of brain chemistry gradually replaced his model with a biological explanation of how the mind arises from neuronal activity. But since mid 1990s, attempts to piece together diverse neurological findings have validated the general sketch Freud made almost a century ago.

The unconscious processing seems to be simpler than the conscious one. It includes a whole range of neural processing from the automatic reflex of some simple animals such as E. coli to automatic actions taken by human. Actually conscious and unconscious processing is similar; they are different versions of the same thing, presumably using at least some of the same neural equipments. The consciously performed actions of the beginner are a stumbling version of the more unconscious actions of the skilled performer. Conscious and unconscious forms blend into each other; there is no hard dividing line. Conscious processing can be summarized as the combination of unconscious processing with feeling or thought - sometimes more, sometimes less, depending on the level of detail or complexity. The brain is constantly trying to automate processes, thereby dispelling them from consciousness; in this way, its work will be completed faster, more effectively and at a lower metabolic level. Consciousness, on the other hand, is slow, subject to error and expensive.
The state of consciousness can be divided into three levels:

• The most basis state is that of being conscious and of not being conscious. The site of consciousness seems to be in or around the thalamus, or it should at least involve interactions between the thalamic and cortical systems.
• A background state is an over all state of consciousness such as being awake, being asleep, dreaming, being under hypnosis, and so on. It includes a range of normal and of "altered" states.
• Specific states of consciousness are the fine-grained states of subjective experience. Such states might include the experience of a particular visual image, of a particular sound pattern, of a detailed stream of conscious thought, and so on. A detailed visual experience, for example, might include the experience of certain shapes and colors, of specific arrangements of objects, of various relative distances and depths, and so on. Much of the most interesting work on "Neural Correlates of Consciousness" (NCC) is concerned with states like these. NCC usually probes neural activity deep down into the cellular level.

Consciousness - Part 2