Prof. Muni Mahendra Kumar
0. The Brain and Citta
According to the Jain philosophy, a living organism is an organic composite of two entities - a physical body and a non-physical/non-material soul. The physical body, which includes the physical brain, is an inanimate material thing by itself. Its animation is derived by the virtue of being intimately associated with the soul whose characteristic attribute is consciousness. In the worldly life, the non-physical soul must have a physical body to function and perform in. And a physical body must be activated/animated by the soul. The part of the soul which animates the body and the brain is called citta. Thus citta is integral with soul and is, therefore, non-physical. The threefold activities of life - mental, vocal and bodily - are all activated by citta. It is true that "without a brain there is no thought" but it is equally true that "Only a live brain can think". And a brain is live because it is animated by citta.
1. The Neural Code
All organisms are active systems, choosing to do what may keep them alive. In higher animals and humans, the most significant selections are made by the brain.
Brain regulates the whole life of an individual by selecting the possible course of action every moment of the life. The nervous system (of which brain is a part) is, thus, much more than a system of communication which is, indeed one of its important functions. The brain contains the reference standards and controls our actions in the light of coming information. Thus programes of the brain can be, in a way, considered as a responding device whose work is determined by the past. But the total human behaviour is determined not only by past but also by plans for the future and the brain is the remarkable apparatus which creates models for the future.
A convenient method to understand the working of the nervous system is to study artefacts, such as computers, that imitate us. It is true that the most sophisticated computer provides a very inadequate model of the human brain. But an understanding of the principles - transfer of information' and the 'software' or system of programmes - can give us much insight of the brain's working. The conceptions of code and language are particularly important.
The units of the neural code are: brain, sense-organs, and nerve-cells. The brain is the controller, issuing orders for actions, after it has decoded (understood) the signals it receives from the sense- organ via the nerves. Nerve-cells are units of brain which initiate most of our actions. We sleep or work, go walking or eating or reading because our brains contain active cells that operate when we choose to do these things. Discussion of whether the cells of the brain do these thing? or allow some other agent - the mind - to work through them will come much later. Suffice it to say here that mind always influences not only our reflex actions but also emotional ones. (e.g. tears roll down at a touching scene in a film). The brain is, therefore, subject to information from outside and influences from within.
2. Simplified Version of Brain Action
How is the brain able to produce all the complex actions of a human life? The essence of this power lies in the great number and variety of nerve-cells, their connections and their activities. Each one of the several thousands million nerve-cells in the human cortex corresponds to one of the following:
- A small part of one particular feature of change going on in the environment.
- Some small parts of a memory-record of past external change or
- Some small part of the instruction for an action that can be done by the body.
This is indeed an over-simplification of the action of our cells from moment to moment. Thus nerve-cells are the letters of the cerebral alphabet. Combinations of them compose the words, sentences, paragraphs, chapters and books that constitute the programs that produce our patterns of behaviour. To understand the language of the brain, it is necessary to know how the nerve cells combine, like letters, to produce units that have meaning like words. Just as language, spoken or written, is used to attain a purpose and grammar is the system that regulates the proper use of language, the brain operates a sort of metalanguage with a metagrammar, which regulates the proper conduct of life, (including speech). We shall now explain briefly how the three sorts of nerve-cells mentioned above function.
3. Physiology of Nerve-cells
The miraculous functions that brains perform depend on the power of nerve cells to produce certain electrical and chemical changes. The nerve fibres are very extended strands of protoplasm stretching away from a central nerve - cell - body. This contains the nucleus, whose DNA is reponsible for making it ready to perform its particular function of sending appropriate messages which take the form of signals passing along the nerve-fibres. There is an electrical potential difference of nearly one-tenth of a volt between the inside and outside of the fibre. Similar voltages across the surfaces of all of our millions of nerve-cells provide the means by which messages are sent and decisions made in the nervous system. Each nerve-fibre is a charged system; it has a source of energy available to allow the propagation of messages. If the fibre is suitably stimulated, a sort of electrical explosion spreads all the way along its whole length. This is the nerve-impulse which is the signal that travels along nerve-fibres. After the signal has passed, there is a 'refractory period' before the next impulse can pass. Each action potential is thus complete, and they are all identical. It is as if there was a train of gunpowder, where each explosion sets off the next. The size of the 'impulse' depends upon the charge at each point. The signal comes out as strong at the end as at the beginning.
The nerve-impulses are thus the basic units of the language, comparable to letters. They do not themselves convey meaning. The meaningful units or words of the brain language are the individual nerve-cells. Differences of quality, such as different tones or visual contours, are encoded in the nervous system by having a different nerve-cell and nerve-fibre for each quality. That is why we have such a vast number of nerve-cells. The brain is essentially a multichannel system. Its method of coding is to make up messages by putting each item of information into a separate channel.
4. The Synapses and Neuro-transmitters
Each cell of the brain or spinal cord called neuron has a number of receptive branches, the dendrites, and a single outgoing fibre, the axon. The dendrites are spread through a limited volume around the cell body and they serve to initiate activity in the cell so that it sends signals along its axon, reaching to a greater or lesser distance. Each fibre entering the nervous system from a sense-organ branches many times and makes connections with many cells in the spinal cord or brain. Conversely, each central cell receives the endings of many incoming fibres and of the fibres a rising from cells elsewhere within the brain. The points where the endings of the axon of one cell meet the dendrites of another are known as synapses. At the synapse, the membranes of the two nerve-cells are pressed against each other, but the contents of the fibres are not continuous. There is, therefore, a barrier between the inside of incoming (pre-synaptic) fibre and that of the post-synaptic cells. This barrier makes it impossible (usually) for the electrical nerve-impulse to spread from one to the other. The transmission is effected by the release from the pre-synaptic fibre of a chemical, such as acetylcholine, to which the post-synptic surface is especially sensitive. The response to the chemical serves to amplify the effect of impulses arriving, so that they influence the post-synaptic cell.
These chemical transmitters have become well-known only in recent years. They are found in the knobs (known as boutons) at the ends of the pre-synptic fibres. There may be up to 50,000 of these little knobs attached to the surface of single cell of the cerebral cortex. They will include branches of several different incoming nerve-fibres. The currents produced under the different boutons will summate. If they are sufficiently close together in space and in time, then they will set up an action potential, travelling a way down the axon of the post-synaptic cell to its ending in contact with yet another nerve-cell, or with a muscle or gland. This process of summation of the effects of the boutons is thus the means by which decisions are reached in the nervous system.
5. Decoding
The signals arriving in various combinations along the sensory nerve-fibres will activate particular nerve-cells. The first stage of what may be called the decoding of the signals in a set of nerve-fibres is by the activation of certain particular cells of the brain by the synapses.
The basic outlines of the patterns of connection are laid down by heredity. These are our pre-program, such as that for breathing. Nearly all of our activities include a part that is hereditary and can be referred to as instinctive. Much more interesting is the question of how these basic patterns come to be combined with other patterns of action of the nerve-cells by the process of learning. This is how we acquire language and the socially transmitted programs that dominate so much of our lives. Even more interesting is the question of how new programs can arise within us, as they certainly do, if we are even minimally creative. These are some of the problems that we hope to face later. However, decoding does not mean that there is some final stage where the message is understood. The decoding is completed only by action or preparation for action.
It should not however be concluded that we are activated only by external stimuli. In fact, many of the nerve-cells go through continual cycles of activity or changes in sensitivity. The effect of incoming impulses is then to alter their frequency of discharge. Whole sections of the nervous system never cease their activities. To take the simplest example, the cells of the respiratory centres send out nerve-impulses regularly every few seconds to the muscles of the chest, from our first breath to our last. Some of these rhythms are due to inherent properties of the membranes of the cells. Others are the result of cyclical chains of nerve-cells, so arranged that they continually re-excite each other. Our behaviour, thus, comes from the combined operations of this vast set of internal rhythms with the inflow of information from the sense-organs. Our task would then be to try to understand how all these millions of cells, acting together, produce the programs of human action.
Our endeavour is to see whether by study of the brain we can also connect its functioning with that of the karman and thereby can improve upon it as an environment for philosophical understanding of the doctrine of karman.
