Consider, for example, one’s decision to move one’s hand to scratch one’s head. One of the first physical manifestations of this movement is an electrical signal that appears in a part of the brain, followed by a whole cascade of chemical and electrical signaling that eventually results in the appropriate pattern in time of tiny electrical pulses – known as action potentials – that are distributed spatially over thousands of nerve fibers, eventually causing the muscles involved to contract and execute the required movement. Although this seems like a simple movement, it is quite complex when analyzed.
For one thing, several joints are involved: shoulder, elbow, wrist, and finger joints. Since muscles can only pull and not push, movement at each joint is controlled by two opposing sets of muscles that should all be properly activated by these patterns of action potentials so that the whole movement is executed with seamless precision and eventually terminated. What directs the fingers to the desired location on the head? What makes the finger movement gentle enough so as not to bleed the scalp with the fingernails? Vision need not be involved, as the movement can be made with closed eyes. What is involved is our unconscious sense of perception of movement and spatial orientation mediated by specialized receptors in joints, muscles, and tendons, in addition to our sense of touch.
The brain must generate the required spatiotemporal pattern of action potentials, monitor the movement, and make corrections on the fly, as in the case of some unanticipated impediments, such as a tight-fitting jacket, for example. How the brain does all this has only been postulated rather vaguely, with no general agreement on how the movement is planned and executed. Moreover, what is often glossed over is how does this volitional act of scratching one’s head – an activity that is purely in the mind – generate a physical electrical signal in the brain?
And this is just concerning movement, whose end result is amenable to observation and precise measurement. When it comes to perception and consciousness, matters are much hazier. If a red rose is placed under the nose, for example, with eyes closed, one would recognize a rose from the fragrance. When the eyes are opened, the redness of the rose is perceived. The sight and fragrance of the rose might evoke memories of a bouquet of red flowers on some happy occasion, which might in turn bring some feelings of nostalgic joy. The perceptions of the smell and color of the red rose and the memories and feelings evoked are subjective – that is, in the mind. No two people would perceive the same smell or vividness of color or experience the same feelings upon exposure to the red rose. This is part of our consciousness as unique human individuals. To say we have a good inkling as to how the brain does all this is a rosy view in the extreme.
Speaking of memories, this is yet another mystery of the brain. Memory is essential to our existence. Without memory, we will not be able to use any information we have acquired, knowledge we have gained, or skills we have learned. We would not remember our own names or recognize the looks and voices of others, or be able to read or write, or maybe even talk or walk! It has long been assumed that memory is stored by some changes in the brain, referred to as memory traces or engrams. Yet, all attempts at definitive identification and localization of these engrams have failed so far to give satisfactory and generally accepted results.
Brain operations have customarily been hypothesized in terms of technologies of the time. In the 17th century CE, the nervous system was conceived as a hydraulic system. Animal spirits would flow from the ventricles of the brain through hollow tubes – the nerves – to muscles, filling them up and causing muscular contraction. After telephone exchanges were introduced in the late 19th century CE, the brain was considered to act as a telephone switchboard that switches connections between incoming and outgoing pathways. With the advent of computers, the brain was likened to a computer performing some complex computations. Movement is thought to be executed as a sequence of commands in a motor program, like the set of instructions in a computer program.
The brain consumes about 20 watts, or nearly a fifth of total body consumption, despite its mass being only about a fiftieth of typical body mass. The brain grew in size over a span of some two million years, from the earliest human species to our species, Homo sapiens (the wise humans), despite its energy demand. To cater for this demand, other high-energy consuming organs of the body were reduced in size, mainly muscle and intestines. The returns for the larger brains were meager for a long time, mainly some primitive tools such as pointed sticks and sharp stone. So what was the drive for larger brains? No one really knows.
Then between 70,000 and 30,000 years ago, in what has been dubbed the Cognitive Revolution1, some chance mutation is believed to have occurred in the brain, with dramatically far-reaching results:
- imagination and abstract thinking, that is, the ability to form mental images, thoughts, and sensations of things and entities that are not physically real,
- a highly developed language that allowed effective communication and the transfer of a tremendous amount of detailed information, and
- amazing manual dexterity. This triad of creative imagination, language, and manual dexterity was a formidable combination that propelled Homo sapiens to become the undisputed masters of planet Earth in a matter of less than 30,000 years. That all our cultures and civilizations are just the result of a chance mutation in the brain is hard to believe, which only adds to the mysteries of the brain.
An English researcher, Rupert Sheldrake, postulated in the early 1980s the concept of what he calls morphic fields. Sheldrake attempts to explain many phenomena associated with living organisms, including instinctive animal behavior, in terms of morphic fields and their interactions2. According to Sheldrake, memory is not in the brain at all, but in the morphic field; that is why all attempts to locate memory in the brain have failed so far. Although morphic fields remain purely hypothetical, and may well be untenable, they are nevertheless an external agency that is being invoked to explain phenomena whose explanation has hitherto been confined, by conventional wisdom, to factors or elements within the organism itself, not outside of it.
In conclusion, the deep mysteries of the brain have so far defied all efforts at unravelling them. But hope springs eternal despite a nagging, somewhat philosophical and tantalizing question: are the thought processes of the brain able by themselves to understand the operations of the brain, or does this understanding require something of a higher order of capacity than the human brain?
- Harari, Y. N. (2015) Sapiens: A Brief History of Mankind, London, Vintage, pp. 22-44.
- Sheldrake, R. (2012) The Presence of the Past, revised and expanded edition, Rochester VT, Park Street Press.