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Biology 202, Spring 2005 First Web Papers On Serendip

Location, Location, Location: Identifying States and Loci of Consciousness

Laura Cyckowski

With each day the reaches of science stretch further and further. Within the field of neural sciences, with every new neurotransmitter discovered, every new molecule stumbled upon, every new hormone identified, new pieces of a bigger puzzle are pieced together. This puzzle aims to explain one of the biggest topics in neural and cognitive sciences, psychology, and even philosophy, and that topic is how human behavior works. Over the years, our view of the human brain has become ever more detailed. Specific loci down to the microscopic level have been identified with highly specific functions, such as visual or olfactory tracts. Even specific reflexes, vomiting for example, have been traced to a particular structure in a certain location. Student textbooks offer diagrams of the brain marked to show specific areas specialized for functions like memory, motor activity, or face recognition. There's once piece in the puzzle, though, that's been missing and shows no signs of being found anytime soon. That is the piece which holds the key to understanding consciousness. Where does consciousness fit in the big picture? Is it a small piece of the puzzle- that can be related to a particular brain structure- or is it the result of a number of structures coming together and thus the "big picture"?

In trying to answer these questions, the first problem to arise is defining consciousness. Most definitions include the idea of awareness of one's internal and external environment; definitions also usually include the idea that consciousness is something subjective and qualitative. The inevitable concern about whether animals are in a conscious state similar to humans has led to two different types of consciousness: phenomenal consciousness and self-consciousness. The first refers to a strictly empirical state of perception. When we see, hear, taste, smell, and feel things we become conscious of them. Under this definition, humans and animals alike are considered to be conscious. The most famous description of this type of consciousness comes from Nagel, who proposes there is a feeling of "what it is to be like" a particular species. To be in a self-conscious state, however, is to be capable of "second-order representation of [one's] own mental states... to be capable of attributing mental states to others" (1) and to "consider oneself as an agent." (2) Perceiving things like sounds, sights, and so on is included under a phenomenal consciousness only, and would not be included in self-consciousness. For example, hearing a sound would not be a self-conscious state but anticipating or thinking about hearing a sound would be.

Scientists come to a fork in the road when dualism and reductionism enter the picture. To a dualist, the brain and all of its neurons are one type of matter which is subordinate to thought, consciousness, and the mind or soul, which is not material entities. A reductionist view collapses the two into one category. The brain and all of it's activities give rise to "things" which we conceive as non-material, namely thought, consciousness, and mind/soul. At one extreme, consciousness might be considered something material since it would have to arise from a cellular level: neuronal firings. Consciousness is then simply an emergent phenomena, a higher function of the brain. Phenomenal consciousness might then be explained by a "building-block approach." (2) A feeling of "overall" consciousness is achieved by an aggregate of various perceptual or sensory experiences. That is to say that visual consciousness could be independent from olfactory consciousness and so on. The question then of which brain structures consciousness could be pinned too is redundant, as a collective consciousness it would be a sum of "sub-consciousnesses" which are manifested throughout the brain.

An interesting case supporting the building-block approach is the phenomenon of blind sight. In cases of blind sight, a patient will be blind in parts of the visual field but still be able to accurately guess locations of objects he or she cannot perceive. Neurologists have suggested damage or interruption in the pathway which splits and leads to a structure where consciousness might be involved. (3) A case highlighting interference with consciousness (or lack thereof) of output processing is jargon (Wernicke's) aphasia, in which there is damage to structures associated with language. Afflicted patients are not conscious of their speech-output and often substitute phonetically similar words and thus produce nonsense words and sentences. In both blind sight and jargon aphasia, consciousness of all other senses remain intact, which still supports a building-block theory.

A consideration incorporating ideas of both phenomenal and self-consciousness is whether or not input originates externally (in the environment) or internally ("within the brain" itself). Many theories of phenomenal consciousness assume sensory input from the environment-- sights we see, sounds we hear, etc. However, sleeping and subsequently dreaming, which are usually considered conscious states (albeit "altered"), need attention. Is dreaming to be considered phenomenal or a higher-order-self-consciousness? What about the events occurring around us while we sleep? If we're awoken by something in the environment it indicates we were still in a state of phenomenal consciousness. But what about our dreams? Are the visual cues during dreams to be considered higher-order because they do not originate from the environment? Some sleep researches suggest that during deep sleep or dreamless sleep we are "alive and [our] brain is functioning, but there are no mental events occurring in which there is any element of consciousness." (4)

In cases of patients being "brain dead" or in a "vegetative state", patients are often described in terms of consciousness on a gradable scale. That is, most usually they are diagnosed "minimally conscious." In a brain imaging study, researchers using MRIs concluded that patients thought to be totally unaware and responsive to any input showed mental activity. In several cases, patients showed brain activity in response to a family member's or friend's voice. (5) These patients may not seem to be in state of self-consciousness but could been seen to be in a state of phenomenal consciousness, in that their "sub-consciousness for hearing" was still present. The building block theory does not, however, hold true. If evidence can be shown for perception awareness in brain dead patients, there should be an "overall" or "emergent" consciousness even if it is not complete, as in blind sight patients. A unified field theory attempts to validate phenomenal and self-conscious states. According to this theory, phenomenal consciousness subsumes self-consciousness, rather than vice versa. In order to experience phenomenal consciousness, a person must already be in a state of consciousness. (5) The so-called "second-order" self-consciousness state is not emergent in relation to phenomenal consciousness but vice versa. This might apply to brain dead patients, who may process input but are not phenomenally conscious because whatever is responsible for the self-conscious state has been impaired.

Patients with split-brains might shed light on which parts of the brain, if any, may be responsible for such states. In such patients, many with epilepsy, the corpus callosum is severed so communication between the right and left hemisphere is suspended, though information may still be sent from the right hemisphere to the left through the brain stem. In one experiment, a researcher showed pictures to the left and right hemisphere of a female split-brain patient. Among the pictures was one of a nude person, which when shown to the patient's left hemisphere. She laughed and was able to explain why and what she saw. When a similar "funny" picture was shown to her right hemisphere, however, she laughed but was unable to explain why. (6) Among the implications with these results is again the question of where consciousness might be rooted-- if it is localized or collective-- and conscious control of outputs, such as laughing. If the picture was shown to the patient's right hemisphere and she laughed, but didn't know why, this might raiser other implications concerning unconscious behavior. It follows that free will is dependent on consciousness. Researchers on split-brains have also found that "basic responses (heart rate, visual conditioned stimulus)" cross hemispheres by way of lower-pathways within the brain and spinal cord. Researches imply this is related to evolution of human consciousness and conclude animals are conscious but at "lower" states. It might be said, then, that animals are incapable of experiencing free will.

Given all of the data, research, and special cases relating to behavior and consciousness, it's easy to piece together conclusions in a number of ways that all yield explanations to satisfy the observations. Whether or not our picture of behavior and consciousness will ever be complete, if a particular brain state is equal to a particular conscious state (or vice versa) then the equation brain equals behavior is irresistible-- which may make Cartesians feel a little "self-conscious."

References

1. Primate Consciousness.

2. John R. Searle, Consciousness.

3. Roger Penrose, Real Brains and Model Brains.

4. Consciousness.

5. Benedict Carey, New Signs of Awareness Seen In Some Brain-Injured Patients.

6. Split Brain Consciousness.


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