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Nervous System


Higher Functions

Higher Functions The frontal lobes are where ideas are created; plans constructed; thoughts joined with their associations to form new memories; and fleeting perceptions held in mind until they are dispatched to long-term memory or to oblivion. This brain region is the home of consciousness, where the products of the brain's subterranean assembly lines emerge for scrutiny. Self-awareness arises here, and emotions are transformed in this place from physical survival systems to subjective feelings. The area of the frontal lobe most closely associated with the generation of consciousness is in the prefrontal cortex. Figure 30a shows four areas, which endow human with fucntions not available in other animal:

Figure 30a Higher Functions
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  1. Orbito-frontal cortex - This area inhibits inappropriate action, freeing us from the tyranny of our urges and allowing us to defer immediate reward in favour of long-term advantage.
  2. Dorsolateral prefrontal cortex - Things are held "in mind" here, and manipulated to form plans and concepts. This area also seems to choose to do one thing rather than another.
  3. Ventromedial cortex - This is where emotions are experienced and meaning bestowed on our perceptions.
  4. Anterior cingulate cortex - It helps focus attention and "tune in" to own thoughts.
The frontal lobes are connected by numerous neural pathways to almost all the other cortical areas and also to the limbic region. These paths are two-way. Information must flow in to the frontal lobes in order for them to function, but a heavy input from below can inhibit activity on the surface and vice versa. This means that a sudden flood of emotion may occlude thought, while an arduous cognitive task may dampen emotion. The ebb and flow of neural traffic is mediated by the neurotransmitters dopamine, serotonin and adrenaline, and any disturbance to these chemicals, or damage to the tissue that is sensitive to them, can have catastrophic effects on the way we think, feel and behave.

Consciousness is remarkably difficult to define. It is variably identified to the soul, the mind, and somehow associated with awareness (Figure 30b). The soul belongs to religious domain, which is not possible to investigate scientifically. It was believed that the mind was in the brain and controlled the body, but was something intangible. The development in neuroscience has brought new insights into the subject of consciousness. This new science has adopted the working definition of consciousness as a state of perceptual awareness. Conscious attention allows us to shut out extraneous experiences and focus on the critical event that confronts us. It recognizes two characteristics to the conscious state: unitary and subjectivity. The unitary nature of consciousness refers to the fact that our experiences come to us as a unified whole. All of the various sensory modalities are melded into a single, coherent, conscious experience. This is the "easy problem" that neuroscience can probe into via NCC.
Consciousness The answer was still elusive at the end of Francis Crick's life, when he was struggling in vain trying to understand the role of claustrum in consciousness. Subjectivity poses the more formidable scientific challenge. Each of us experiences a world of private and unique sensations that another person can only appreciate indirectly. If the senses ultimately produce experiences that are completely and personally subjective, then we cannot arrive at a general definition of consciousness because there would be an infinite number of them. This is the "hard problem" of consciousness. According to some researchers, science cannot take on consciousness without a significant change in methodology, a change that would enable scientists to identify and analyze the elements of subjective experience. Others argue that we only need an underlying theory. Just like the Newtonian mechanics, one theory is sufficient to describe the multitude of orbits and trajectories.

Figure 30b Consciousness
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See "Integrated Information Theory of Consciousness" for recent development in the study of consciousness.

Free will is a Western believe having its root in an omniscient being, who created man and woman after His image and conferred His subject
Original Sin with the "free will" - the power to make decisions of their own. Unfortunately, His creation made a bad choice of falling into the temptation of a serpent ... (Figure 31a). This tale goes down in history affecting every facet of life in Western society. In particular, the system of criminal justice assumes that each person has a "free will" to act, the bad behavior should be punished accordingly because of his/her bad choice.

Figure 31a The Original Sin [view large image]


Free Will The idea of "free will" has been the subject of endless debates - about its existence, interpretation, ... Now its nature can be tackled by the new biology of mind. According to Freud's discovery of psychic determinism - the fact that much of our cognitive and affective life is unconscious - there is not much left for freedom of action. Experiment on the correlation between electrical activity of the brain and movement (lifting a finger for example), reveals that the electrical activity precedes the movement by 200 milliseconds. It is proposed that the process of initiating a voluntary action occurs in an unconscious part of the brain, but that just before the action is taken, consciousness is recruited to approve or veto the action. In the 200 milliseconds before a finger is lifted, consciousness determines whether it moves or not. Thus, our conscious mind may not have free will, but it can freely modify inappropriate behavior (Figure 31b). This is the reason for the laws in our society to hold all of us accountable for our own action. It is suggested that we should update our idea of free will to mean self-control over our behaviour. In other words, the brain sets criteria, plays events out internally, chooses the best option, then makes thing happen; but it could always have turned out otherwise by picking another

Figure 31b Free Will [view large image]

option. By this definition of free will, it is neither predetermined nor completely random. It is this mechanism that lets us to act out according to our own volition. See "connectome" for an up-to-date view about the human mind.

TMS Experiment A curious free will behavior is reported by experiment with Transcranial Magnetic Stimulation (TMS). This gadget is used routinely to manipulate involuntary movement by stimulating particular area of the brain with pulse of magnetic induction (Figure 31b1). In one experiment the decision to use the left/right hand to do something is pre-recorded. Then the pulse is introduced to direct the movement. Although the movement contradicts with the initial decision, many participants felt as if they had made the move according to their own free will. It seems that the conscious mind tends to assume itself in total control even though it is not.

Figure 31b1 TMS Experiment on Free Will [view large image]

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