Conventional Theories of Consciousness
It has commonly been proposed that mind and consciousness are products of neuronal activity and arise from brain activity. Conceptually, this is similar to how light arises from a light bulb, but isn't the same as the underlying processes taking place within the light bulb. A number of different theories have been proposed to account for this phenomenon, which portray consciousness as an emergent property of brain cell activity in the brain. Specifically it has been proposed that consciousness, may arise
- where brain cells connect together
- through a synchronous activity of brain cell networks in the brain and
- as a novel property of computational complexity among brain cells.
It is further argued that brain cells and their chemical connections are the fundamental units of information in the brain, and that conscious experience emerges when a critical level of complexity is reached in the networks of brain cells. Evidence to support these theories have come from the observation that specific changes in function such as personality or memory are associated with specific brain injury, such that people with specific head injuries or brain tumors may lose certain aspects of their consciousness. In addition, special scanning devices such as MRI and PET scanning have also shown a correlation between activity of brain cells and different mental states. These have shown that when someone has a specific thought, groups of brain cells may become active, as measured through their use of oxygen or glucose. Although, these provide evidence for the role of brain cell networks as an intermediary for the manifestation of thoughts, they do not necessarily imply that those cells also produce the thoughts.
Many have argued that these theories cannot fully explain the observed features of consciousness. Their limitations can be divided into four broad categories and involve a lack of mechanisms to account for the occurrence of:
- 1) The nature of subjective experience, in other words how do thoughts somehow arise from chemical processes in the brain cells.
- 2) The binding of activities that are taking place all over the brain into unitary objects such as consciousness or vision. If we take the example of vision, when we look at something this involves more than 30 areas of the brain that are spread in many different parts of the brain. How then do all these different processes bind into a single conscious state of seeing something?
- 3) Transition from pre-conscious processes to consciousness itself: How do chemical processes that are not conscious events lead to a conscious state?
- 4) Free will. We all have free will and we use it in our everyday lives to make decisions, however if everything to do with our consciousness was determined by brain cell activity then how do we have free will to chose. Everything should be predetermined. These have led to alternative explanations for consciousness.
In general the evidence to back up the theory that mind and consciousness may arise from the brain has come from the clinical observation that specific changes in function such as personality or memory are associated with specific areas of damage to the brain, such as those that occur after head injury or a stroke. This finding has been further supported by the results of studies using functional MRI and PET scanning, in which, as described above, specific areas of the brain have been shown to become active in response to a thought or feeling. However, although these studies provide evidence for the role of networks of brain cells as an intermediary for the manifestation of thoughts, they do not necessarily imply that those cells also produce the thoughts (maybe add about correlation). In fact today due to a number of significant limitations, many scientists have argued that brain-based theories alone cannot fully explain the observed features of 'the self'. These limitations can be summarized into four broad categories:
The most obvious limitation of such theories is that they do not provide a plausible mechanism that may account for the development of 'the self' from brain cell activity. The theories simply propose potential intermediary pathways that may be mediating consciousness but do not answer the fundamental question of how subjective experiences may arise from the activity of brain cells. This is a point that has been summarized very well by the well known University of Oxford neuroscientist Professor Susan Greenfield. Even though she supports a brain based theory, in one of her articles she nevertheless concludes: '.just how the bump and grind of the neurones and the shrinking and expanding of assemblies actually translate into subjective experience - is, of course, another story completely.'
How do brain activities that are distributed within multiple areas of the brain bind into a unitary sense, such as occurs with vision, or the development of a coherent sense of self? In other words, how do we go from multiple inputs from millions of brain cells to a single picture or a single sensation of the self?
The theories proposed do not account for how an event that is pre-conscious (in other words chemical or electrical events that are going on in our body but we are not 'conscious' of) becomes conscious, other than to say that it 'somehow' occurs at a critical point.
A fundamental part of our lives involves the notion of free will. We are judged in society based upon our intentions and actions and the brain-based views expressed above cannot account for this. If correct, they would mean that our lives would be completely determined by our genes and environment and hence there would be no place for personal accountability. Can you imagine the situation that would arise if everyone claimed that everything they did was due to the action of their genes in combination with their environment? No one could really be held accountable any more! Thankfully, society still runs with the notion of free will and personal accountability.
These and other limitations with the conventional views have led some scientists to seek alternative explanations for consciousness.