Higher Functions & Intelligence

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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 30 shows four areas, which endow human with fucntions not available in other animal:
 

Figure 30 Higher Functions

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 31a). 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.
 

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 31a Consciousness

The nature of free will is another issue that can be tackled by the new biology of mind. Free will is the ability to act or make choices as a free and autonomous being and not solely as a result of compulsion or predestination. 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.
 

Figure 31b Free Will

Intelligence

 Psychologists had been arguing about the definition of intelligence since there are different types. Finally in 1993, they came up with the "Three Stratum Theory" as illustrated in Figure 31c. Sitting at the top of this one-plus-many relationship is the General Intelligence Factor (the g factor) under which are the broad abilities and further down in the ladder are specialized skills related to the broad abilities. Fluid intelligence is about learning, reasoning and problem solving; while crystallized intelligence is the recollection of previous experiences, such as vocabulary, cultural knowledge, ... The other abilities in the middle of Figure 31c are self-explanatory. By examining wildly separated twins and non-kin adopted into the same home, it is found that heritability (of intelligence) is less than 30% before starting school, rising to 80% among western adults. Thus, nature seems to win over nurture at the end as revealed by IQ tests. IQ test was invented in 1904 to identify children who would fail
 

Figure 31c Intelligence

Figure 31d Brain Anatomy and IQ

elementary school without special help. Today their use can be considered contentious, partly because they do not find equal amounts of intelligence everywhere. It is culturally bias.
 
Figure 31d shows the purported correlations between brain anatomy and IQ.

The informal definition of intelligence in dictionary is the capacity to acquire and apply knowledge and the faculty of thought and reason. In general it is perceived in terms of memory, reasoning, responsiveness, ... In neuroscience intelligence is vaguely related to brain mass, neural connections, and transmission time, these properties are loosely associated respectively with memory, reasoning, responsiveness in the layman's terms. Recent studies in the 2010's suggest that human intelligence has reached its limits beyond which any attempt for improvement would bring only diminishing returns.
 

Figure 31e Brain Mass vs Body Weight

Figure 31f Limits of Human Intelligence

A more detailed explanation is provided in the followings.

 1.Brain Mass -- It was thought that heavier brain means higher intelligence because it would have more neurons (gray matter) and axons (white matter). However, "more" doesn't mean "better" as shown by the Kleiber's Law in Figure 31e, in which human is at the apex of intelligence. Further increase in brain mass entails more increase in body weight such that the add-on brain cells are allocated for neural housekeeping chores (such as controlling more muscle fibres) unrelated to intelligence.

 2.Neural Connections -- The human brain contains about 120 billion neuronal cells, with an approximately equal number of non-neuronal cells (glial cells). These cells pass signals to each other via as many as 1000 trillion synaptic connections. The communication networks (at about 2% of our body weight) consume about 20% of the energy that we expend at rest. In newborns, it is an astounding 65% making the infants to rely on parental care for its survival. Further increase in neural connections will demand more resource at the expense of the other biological processes in our body.

 3.Transmission Time -- The transmission time between neurons depends on the traveling distance. That's why the motion of elephants appears to be rather slow. The transmission time is also determined by the speed of the signal. It is found that thicker axons carry signals faster. This advantage is negated by greater consumption of energy and occupies more space (the same trade-off as for more neural connections).

4.Neuron Density -- It is found recently that unlike other mammals, cortical neurons in primates enlarge very little as the brain increases in size. This kind of packing strategy allows for greater number of cortical cell as brains enlarge; and it also permits faster communication, because the cells pack more closely. However, thermal motion triggers random firing of the action potential if the axons or neurons become too small.
 Restricted by the above-mentioned constraints, it is doubtful that a major evolutionary leap could lead to a smarter brain. The evolution of brains started about 600 million years ago. Since then all kinds of animals have now evolved to a point where the brain circuits have arrived at a similar design for running tasks such as vision, smell, navigation, ... Such evolutionary convergence usually suggests that a certain anatomical or physiological solution has reached maturity so that there may be little room left for improvement. Figure 31f shows the various options for improvement in brain structure and the trade-offs in each.

The class of Cephalopods includes octopuses, squids, cuttlefish, and nautiluses. It is within the phylum mollusks which encompasses such animals like clams, snails, and octopuses. Cephalopods has the distinction of the most intelligent invertebrate on a par with the cleverer vertebrates such as chimps, dolphins, and crews. Although there are differences in synaptic chemicals (they have fewer) and their axons are not covered with myelin, there are lot of similarities between the two kinds as shown in Table 03. If consciousness is defined as the notion of "self" and making decision based on previous experiences, then the cephalopods have at least the rudimentary form as experiments show repeatedly that they can navigate maze, use tools, mimic other species, learn from each other, and solve complex problems (such as eating clams with closed shell and trying to devour a hermit crab with stinging anemone on its back). The earliest ancestor of cephalopods is probably a snail-like creature existed about 500 million years ago. The present day nautilus is a living fossil not much different from those cephalopods in the ancient time. While their brains are nowhere near as complex as their
 

Figure 31g Cephalopods

younger relatives, they have many of the same abilities in learning, memory and spatial awareness. It seems that they have beaten the mammals to develop intelligence by at least two hundred million years (see Figure 31g).

Structure	Similarity
Location	In the head (unlike the ganglia running along the length of the body in other mollusks)
Lateralization	Brain split into 2 halves connected by a bundle of nerve fibres
Lobes	Brain divided into specialized lobes
Sulcus	The lobes are folded to increase surface area
Neuron Distance	Inter-neuron distances are shorter (than the other mollusks) to allow faster communication
Other Parts	There are corresponding parts to the hippocampus and cerebellum in higher vertebrates

Table 08 Similarities between the Brains of Cephalopods and Clever Vertebrates
 Since these two kinds of creatures developed their brain along different pathways, the specializations listed in Table 08 indicate that they are the minimum requirements for intelligence.