THE BRAIN: KEY FACTS

None of us can remember it, but our first light, sounds, and our first physical contact with the outside world after being born must have been the greatest fireworks extravaganza. 200 billion brain cells lit up with sensory stimuli they had never experienced before - imagine this happening to an adult!

That was more brain cells (neurons) than we will ever have. We start losing some straight away - by our first birthday we are down to about 120 billion - and more slowly from then on. Even though we can generate some new brain cells, by age 35 we are down to about 100 billion, half the original, although these are now bigger in size and have formed trillions of interconnections (synapses) between them, so the size of our brain increases.

We lose brain cells (and synapses) throughout our lives as we continue to form a brain unique to ourselves. We lose the options we do not use, while we reinforce the connections we use the most, so we shape our personality and our own ways of thinking. Therefore, not all of that loss is bad news; it is like the brain sculpts a clear form out of a rough-hewn block of unshaped marble. And there are things we can do to slow down the loss of brain cells, through the right diet and exercise (same as for a healthy heart) plus also challenging the brain with new and difficult things on a regular basis, outside our habitual patterns.

Unused parts of our brain are pruned away also for greater efficiency, because neurons and synapses consume so much energy, which is partly why brainy people find it difficult to bulk up muscle, no matter how much exercise they do.

The brain undergoes its greatest changes in the first two to three years, and then in adolescence. In the first years of life there is an explosion of new synapses, but then these are cut down in number to make the brain more efficient. Also the process of myelination makes the connections more permanent but also harder to change, in other words, information is stored long-term but our thought-patterns or personality become difficult to reshape.

A good example of how the brain shapes itself to its environment is how babies hear the sounds R and L . All young babies can distinguish between these sounds, but in the Japanese language there is no difference, so Japanese babies quickly lose the ability to differentiate between the two. If that's how early we begin to distort reality, the practical lesson is to be more aware of our biases, to be wary of our perceptions, and never presume we can see the whole truth.

Certain ways of thinking are programmed into our own individual brain by our genes. Several genes may combine in determining any single characteristic, whether we are happy or intelligent, for example. However, we are not prisoners to our genes. Unlike animals, we can play to our strengths plus also try to counter any negative mental tendencies we have inherited.

This is the most striking difference about the human brain. Those of animals are almost fully formed at birth, but we continue to reshape ours throughout our lives.

At any one moment our brain is receiving about 100 million pieces of information through the ears, eyes, nose, tongue and skin. We are not aware of everything that happens in our brains, only some of the sensory inputs we receive and just the top level of our thoughts. Underneath that, there is an ocean of activity, from how the brain controls numerous bodily functions and the co-ordination of our muscles, to our subconscious beliefs and seemingly forgotten memories, all of which make us a unique human being.

Brain cells are interconnected through trillions of projections - dendrites and axons. The point where those contact and connect with another neuron is a SYNAPSE. One neuron may be connected to upwards of 40,000 others. The more synapses we have, the more powerful our brain. Every time we learn or experience something new (real knowledge, not bits of information,) the synapses rearrange themselves and the whole of our brain gains processing power.

This is a simplification, of course. How the brain works is a great mystery, and some brain experts believe we will never understand it. It certainly bears no similarity to the storage of information in electronic form, such as in computers. It is more like an orchestra which composes and plays multiple scores, but each tune then changes every instrument and the orchestra itself. Even this is not a great analogy for the complexity of the brain.

The brain uses both electrical and chemical signals for communication between neurons: electrical signals give it speed, while chemical neurotransmitters convey a greater variety of signals.

The brain is an organ, but it could be said it is several organs put together, the difference being that all parts of the brain need to co-operate in complex ways for any one part to function fully.

Here is a basic list:

· The CEREBRUM is the outermost layer, and the outermost layer of that is the CORTEX (Cerebral Cortex). Its grey matter is made of NEURONS, its white matter of connective tissue, DENDRINES AND AXONS. The cerebrum controls our thought processes and decisions, but parts of it specialise, most notably its left and right halves dictate different aspects of logic, language, imagination or artistic creativity. And there are areas assigned to much more specific tasks, such as different aspects of speech.
· The CEREBELLUM co-ordinates movement and is important in memorising set patterns such as playing a musical instrument or learning to dance.
· The BRAINSTEM regulates body functions such as our heart rate, and contains other specialised parts within itself.
· The LIMBIC SYSTEM includes the THALAMUS and HYPOTHALAMUS. The former is like a processing and mediating centre. The latter controls our basic instincts and drives and is responsible for things like hunger, digestion, various hormones and our sex drive. The AMYGDALA control fear and help to invoke fearful memories. The MAMILLARY BODIES help to store related memories. But it must be said that each of those functions involves more than one part of the brain.
· The HIPPOCAMPUS controls learning, memorising and recalling and is important for storing long-term memories.
· The SUPRACHIASMATIC NUCLEUS is our ticking body clock, and the PINEAL GLAND produces melatonin which sends us to sleep.
· The CORPUS CALLOSUM is like a bridge between the left and right sides of the brain.

This list is not exhaustive and, of course, there are other parts of our nervous system outside of our brain, notably the spinal chord.

Men's brains are wired differently from women's. Male brains appear to be wired with more connections between front and back of brain. Women have more connections left to right. This study found many differences in the way the brain works in the two sexes which appears to show male and female brains are complementary and designed to work together.

CONSCIOUSNESS

How the brain works may never be fully understood but that is a different question to explaining what consciousness is, or what we mean by consciousness. The editor's view of consciousness is that it is less of a mystery than it is made out to be, although an extremely complex phenomenon, and no less a miracle and a marvel.

Since our consciousness grows from the day we are born, it seems to me that consciousness is the collective sensation of a multitude of complex stimuli received from the outside world (which inform us we are a separate entity from it) as well as stimuli from our bodies, plus the interaction between interconnected parts of the brain communicating with each other. It is the very nature of neurons to generate or register sensation, either individually or collectively if they are interconnected.

It seems obvious to me, there is nothing outside the physical reality of the brain, the matter and electrical chemistry, and we do not need anything else to explain consciousness.

This awareness is no different to muscle cells in a dish reacting to an electrical signal, this time with movement, or the contraction of a group of muscles on a carcass after an electric shock. Whereas a muscle cell reacts with movement, a neuron reacts to the same electrical signal by registering (knowing) it has received it and probably emitting an outward signal in response. A single neuron is aware of a simple stimulus and reacts by registering this information, whereas our brain registers all the activity taking place within it on a large scale and it is this collective complexity we perceive as consciousness.

In 2019, researchers from Kyoto University grew cerebral organoids. They were grown using pluripotent stem cells in a specially-designed culture medium. These lab-grown simple brains then showed neural activity. Journal: Stem Cell Reports.

Once neurons interconnect, they organise. We may not understand how, but this organisation then enables the brain to choose what to do, a state of higher consciousness. The brain itself becomes the 'I', the self which can then tell parts of the brain what to do.

A comparison I have heard, not an analogy, is looking at a city and asking, 'Where is the economy located?' Or, 'How is the economy created?' The economy is real but it is our conception of a group of activities which we have chosen to call the economy. We could have chosen a different group of activities and called it the economy, or called it something else. The economy does not reside anywhere special, but a person choosing to use a taxi rather than the bus is as much part of the economy as a large company or a bank. To that man, his taxi is much more significant in the economy at that moment than any large company or bank. It is a question of what we choose to perceive and what we choose to call it.

In other words, we have chosen to assign the word consciousness to something which is not a singular, clearly defined entity or phenomenon, but a collection - a vast, ever-changing collection of brain processes.

There is a fault in the logic of some who try to explain consciousness, and I only discovered this recently while listening to a brain surgeon talking on the subject. He was talking about the great mysteries of the brain, but then he added that "We do not understand how our thoughts and feelings, our conscious self arises."

That is true but the statement reveals an error. Our thoughts and feelings are not our consciousness. Thoughts (and feelings, even though they also have a hormonal dimension, not just neural) are specific events in time. Consciousness is very different. It emerges and develops slowly over the entirety of a lifetime.

As we grow neural connections from the day we are born, these become more and more organised. We then add a growing perception that our mental processes are different from those of others, so from simple consciousness we go to higher levels of self-consciousness. We have already said, there is nothing outside involved in generating consciousness, no soul, for example, and it is no specific brain cells that generate consciousness - it could be called a by-product of what they all do collectively. The point here is that it is not even a specific function of the brain. There could be highly intelligent individuals in a hypothetical culture different to ours who are highly conscious of their thoughts and feelings but not at all conscious of their consciousness, and they would have difficulty understanding what we are talking about, not because consciousness does not really exist, but because it is something we have chosen to define as such, whereas they have not yet considered it.

Is the mind a separate entity from the physical reality of brain matter? This is a totally different question. The mind can only exist and be stored in brain matter just like software can only be stored in hardware but, again, 'mind' is what we have chosen to call the collective information stored in, or currently being registered and its method of being processed. So it is possible to say that the mind is something separate without implying it exists outside of, or independently of brain matter.

None of this is to diminish the wonder of consciousness, not any more than understanding how the stomach and the liver work reduces the body to a machine, or an understanding of hormones reduces our feelings to organic chemistry. Quite the reverse, it highlights the marvel of a lump of matter generating a whole non-material world, the world of complex sensations and abstract ideas. It points to levels of design and organisation in that lump of matter beyond human comprehension.

EDITOR: Consciousness is subject to continuing research, so we list notable links below. This article is intended as a headline and an invitation to contributions.

LINKS:

A letter from John K. Smyrniotis to professor Jim Al-Khalili, Dept. of Nuclear Physics, University of Surrey, on the paradox of the quantum world.

A brief summary by Professor Susan Greenfield