Neuroscience and Karma ► 10. Perceptive - Touching - Pain, Seeing and Hearing

Posted: 06.07.2015

0. Jain Epistemology II

Sense-organs (Indriya)

In the preceding chapter, we had seen that perceptive cognition (mati-jnana), which is one of the five types of knowledge, is born with the help of sense-organs. In other words, sense-organs are essential instruments of perception. One way of classification of living organisms, according to Jain philosophy, is based on the number of sense-organs possessed by the organism. Thus, there are five classes: One-sensed organism, two-sensed organisms and so on. Now the worldly existence of any organism in a particular class is the precise result of the combination of fruitions of various sub-species of karman but they belong mainly to two species - body-making (nāma) karman and life-span-deter-mining (āyuṣya) karman. The entire vegetable kingdom belongs to the class of one-sensed organisms i.e. they possess only one sense-organ - that of touch.

Jains divide each sense-organ (indriya) into

  1. (bhāvendriya) sense-organ qua psychical i.e. the ablity of the soul to have various sensuous experiences
    and
  2. sense-organ qua physical (dravyendriya), i.e. the physical sense-organ.

Thus, when it is said that a one-sensed organism possesses only the sense of touch, it is meant that the body of these organises are equipped only with the instrument of touch perception (one dravendriya). On the other hand, pancendriya i.e. five-sensed organisms would have all the five physical sense-organs. It should be remembered that;he capabilities of the soul (bhāvenriya) is empirically useful only when its counterpart dravyendriya is available.

We have also seen in the preceding chapter that all the five classes. Even the one-sensed organisms are not bereft of mati-jnana. This means that one-sensed organisms (e.g. plants) have the sense-organ of touch and so are possessed of mati-jnana - perceptual cognition - through this. Since the sense-organ of touch is also the instrument of experiencing/ pain, all one-sensed organisms must experience pain also. Pain and pleasure are the results of the vedniya or feeling-producing karman which has two sub-species (a) pleasure-producing and (b) pain or suffering-producing. These feelings are experienced by all organisms from one-sensed to five-sensed. We shall discuss the mechanism and programs of touching, seeing, hearing as well as experiencing pain in this chapter.

1. Programs for Perceiving

Without a continual flow of information from specialized sense receptors, the brain would be cut off, not only from the external environment but also from an awareness of the body's internal states. Out of the traditional 'five senses', sense of touch, which includes pain, is a 'near sense' while seeing and hearing are 'distance senses' equipped with distance receptors. Though thousands of sensory messages are received by the brain every second, only those which are important are 'perceived' while the rest are ignored. Thus, there is a remarkable distinction between sensation and perception. The messages or signals may come from events far away as in seeing, or at the surface of the body as by touching, or actually within it as when feeling pain.

2. The Cerebral Cortex and Perception

The cerebral cortex is an immense folded sheet of layers of nerve-cells arranged in columns. The nerve-fibres bringing signals from the sense-organs, via the thalamus, enter the sheet from the inside. They are arranged in a regular pattern or map, which exactly reproduces every point of the receptive surface of the body, in the correct relations with its neighbors. Thus there are cortical maps for vision, for hearing, and for touch. It is interesting that there are no such detailed maps for smell or taste, which do not have the same power to detect 'shape', at least in man. It is the cortex that asks meaningful questions and so dictates the whole perceptual process through its connections with the mid-brain. But more interesting problem is to find out how the cortex uses the messages it gets from the sense-organs to answer its questions and ask more questions. This is the serial process that we call perception.

3. Touching and Pain

A. The Skin

The skin contains several different sense-organs, which between them serve the various senses that we call touch, pressure, temperature, and pain. Some of these sensory cells are large and conduct signals rapidly. Others are smaller and slower and still others are free nerve-endings, very thin nerve-fibres not attached to any definite receptor-structure in the skin. Each different sort of nerve-ending provides signals for a different sensation. During ordinary life, sense-organs are part of the system of exploratory programs which an animal or man continually employs to satisfy its needs. The senses of touch, and of pressure, mostly come into action when we do things with our hands and feet. Each of these types of receptor is activated by a somewhat different sort of pressure or deformation of the skin. The various types of sense-organ in the skin do not work independently, and the sensations we feel there, such as degrees of smoothness or roughness, pressure, tingling, tickling, or movement are the result of collaboration at both the spinal and cortical levels between the various signals.

B. Cortical Areas for Touch

There are three well-known tracts leading from the skin to the brain. A large area of the cerebral cortex receives the signals from these pathways, all laid out in a regular map, corresponding to the topography of the body surface, but with greater areas for the more functionally important parts. These 'somatotopic' maps are a fundamental feature of the cerebral computer, as they are also for vision. A difference between touch and pain, is that there are active programs for gaining information by touch. We learn to recognize the feel and shape of things, whereas pain is basically inflicted upon us and is formless. Correspondingly, pain has no cortical representation. The symbolic significance of signals of touch are determined by much more complicated systems of reference, after they have passed through thalamus to the cerebral cortex.

C. Programs for Avoiding Damage

Every animal must have programs to ensure withdrawal from harmful situation and no viable organism can be without it. Such programs have obvious advantages for survival. Pain is a warning to avoid further damage. The complex pains that we suffer, are devices necessary for survival. Even the highest organisms have some simple withdrawal response. A child does not have to learn to draw away its hand from a hot object. The flex or reflex ensures that it pulls it away even before it feels the pain and howls. But the child soon learns not to do it again.

All sensations are subjective. What is so special about pain and pleasure? Experiences of pain are sensations, like the associated experiences of the material events that accompany them. The difference is that pains and pleasures are intimate and personal to oneself. They cannot strictly be shared because they are signals that carry warning or reward to that particular individual alone.

D. Pain and Suffering

Suffering of pain varies a great deal between individuals. The same sensation signals from a toothache, for example, affects each person differently. The process by which the brain converts raw sensations, into suffering is complicated. While the sensation is equal to the power of stimuli, suffering varies by many factors, some within the body and the others without, some examples show that the expression of pain depends upon past experience and culture which means that past experience has a great influence on what we feel and suffer, as it obviously does upon what we know.

Many investigators have sought for a special set of nerve-fibres carry ing signals of pain, but no one has ever been able to prove that there is any particular type of nerve-ending in the skin that generates 'pain', as the rods and cones generate 'vision1, the organs of the ear 'hearing', or those of the nose 'smell',. Those are all 'distance receptors', and the signaIs that they send serve to symbolize events faraway. Pain, however, is essentially in or on the body, and it indicates that there is derangement of some sort in the bodily activities. In order to find the nature of this derangement, what we should look for is not specific pain-sense-organs, but the disordered activity of other sense-organs. To a large extent this is what in fact has been found by recent studies of the physiology of pain.

E. Interna! Pains

Though there is no known cortical centre for pain, it must, in some way, become connected with the cortical analysers, otherwise we should never be able to learn to avoid external events that are likely to be painful. What is the physiological basis of pain? Pain, probably, results from disordered nerve discharges, especially if they involve impulses in certain of the thin nerve-fibres called free nerve-endings. These are the simplest of all sensory nerve-terminals and they occur not only in the skin but also in some internal organs, especially in the walls of arteries and in the heart. This raises the question of how we feel internal pains. The answer is paradoxically that to a large extent we don't. For instance, cutting or pricking the stomach or intestine does not give pain. What does hurt is dragging or pressing them. The pains that we feel as headaches are probably in the blood vessels of the brain.

F. Regulation of Pain - Reticular Formation

If pain is not felt in the cortex, is there any other part of the brain in which it can be said to be located? From the spinal cord, three main pathways lead upwards to the brain. One of these three pathways consists not of long straight-through fibres but of a series of little neurons with axons that are small and short and therefore called 'reticular' or 'net-like'. This reticular system is a very complicated set of cells. These can send signals to many different areas. The reticular system is thus not only central in position but also in the fact that it communicates information very widely. It is also central in its functions in the sense that it regulates the whole state of activity of the brain, for example, in sleeping and waking.[1] The nerve-cells of the reticular formation can produce the substance enkephalin, injection of which kills pain in the same way as does morphia. Enkephalin is probably the neurotransmitter involved in synaptic transmission in these reticular brain centres. Morphine thus acts by imitating the action of enkephalin in stimulating the nerve-cells that switch off the responses to traumatic stimuli, including the subjective phenomena of pain. This is the brain's program for reducing pain. However, in extreme cases, where the brain is not able to reduce or regulate pain, it just gives up and resorts to withdraw itself, resulting in "unconsciousness" or fainting. Once again we see how actively the brain regulates everything that is allowed to enter it, even pain.

G. Pleasure and Pain

Some of these central regions art not concerned with pain but are pleasure centres. We do not yet know enough to be able to say whether the pain-inhibiting sets of cells are identical with these that produce pleasure. Is pleasure to be regarded as the absence of pain, or possibly vice versa? Do our programs seek to maximize pleasure or minimize pain, or both? The important point is that there are here what we might call the reference systems that set the course of the whole living control system. Their operation largely determines the ends or aims of the animal or man. These brain regions and the programs they produce are determined by vedniya karman, heredity, and, no doubt, modified by ex-periei.ee. These controls are there to provide the objectives that we seek for in life. It is not too much to say that these systems largely determine what human beings do. But human life is not simple. Other types of program intervene, as it were, on top of these fundamental ones of pleasure and pain that are produced by the actions of the reticular and reward centres. So evidently there are activities in this part of the brain that regulate what we commonly call emotional feelings.

H. Surgical Relief of Pain

Discoveries about the central grey matter have been used in the relief of human pain. Intractable pains are said to be relieved by lesions in the medial part of the thalamus, or by cutting the cingulum bundle, which connects the frontal cortex to the hippocampus. It is clear in any case that there is no one single 'centre for pain' in the brain. The cerebral system does have distinct parts, but many of them interact for the performance of each program of action. Pain is the result of a disordered operation of a program for exploring the world in the immediate neighborhood of the skin, or of the operations of some internal organ(s) of the body. The disordered signals serve to symbolize that something is wrong and this sets off the programs that may put it right, which in man may be very complex. Pain may initiate the brushing away of a wasp, or be the stimulus for the foundation of a research institute for the treatment of cancer.

4. Seeing

A. Structure of the EYE

Although seeing is not like photography, we shall begin by saying that the eye is, in some ways, very much like a camera. It has a lens and a diaphragm (the iris) and a focusing device. What is more, the first step in the process of vision is a photochemical change somewhat like that in a photographic plate. The retina contains a mosaic of more than or hundred million separate receiving elements of two sorts, the rods ant cones, each of which detects a tiny part of the image that is thrown on it by the lens, producing a minute electrical or chemical change. Only the cones arc sensitive to colors and most of them are concentrated near the centre of the eye. Here there is a small area, the fovea, containing only about 30,000 receptive cones. These perform nearly all the detailed work of seeing, except in dim light. In order to see things, we have, therefore, continually to explore them by minute movements of the eyes around them, examining the part we want to see by the fovea. This is of fundamental importance for our system for think in gab out vision because the program that control these eye-movements, largely determines what we see.

B. VISION

Vision is not like taking a series of photos but is part of a whole life-system. Thus vision is a dynamic process, using a series of scans, but these are not rigidly determined as in a television raster. They are varied according to the nature of the scene itself and the previous experience of the individual. Moreover the scanning does not work by converting the information in the spatial scene into a single channel, but puts it into many parallel channels, which maintain the spatial relations, so in a sense the original picture is reproduced on the cortex, but modified and much expanded. We can regard all vision as a continual search for the answers to questions posed by the brain. The signals sent from the retina constitute 'messages' conveying these answers.[2] The brain then uses this information to construct a suitable hypothesis about what is there and a program of action to meet the situation. The sequence of processes involved in the act of seeing do not therefore really begin in the retina, but involve the brain. Nevertheless it is convenient to ask just how the retina composes its messages. The rods and cones are the light-sensitive elements. They contain special pigments, which change when the intensity of light failing on them varies. This change alters the electrical potentials of the cells, so that the pattern of light thrown by the lens produces a corresponding pattern of electrical and chemical change in the various neurons which make up the retina. These impulses in the optic nerve-fibres at each moment of scanning a scene are the answers, in code, to the 'questions' that had been asked at the previous moment. Of course, if something quite unexpected happens, it is seen even though it had not been anticipated. The point is that what goes on in the retina is not merely the recording of a 'picture', but the detection of a series of items, which are reported to the brain. If the eyes are prevented from moving, the signals fade within a second and no picture can be seen.

C. Physiology of Vision

Human photoreception is a complicated process. We are able to encode all sorts of aspects of the world and to decode the signals and act accordingly. Our eyes have lenses and we examine the pictures or patterns thrown upon the retina. The task therefore is to understand how the brain is able to decide appropriate responses to many different patterns. Perception is an active search for meaningful cause and the brain builds program, that guide the search. These programs may possibly be something like those that artificial intelligence workers devise for pattern recognition with computers. Perception involves making structural descriptions from the data and testing interferences as to what these data mean for us. The brain presumably has programs for examining features such as brightness, corners, edges and so on, in order to find, fire, points, then lines, regions, surfaces, bodies, and eventually objects that have meaning or use. The brain reads the letters, words, sentences, and paragraphs of the visual code. The optic nerves carry the information to at least three parts of the brain, the midbrain, cerebellum, and through the thalamus to the cortex. All these parts are interconnected and concerned in any act of vision, but the first two deal mainly with detailed control of the eye movements. Deeper in the centre of the midbrain are motor nerve-cells, each of which has its own 'movement area' so that it sends signals when there is movement in a particular part of the visual field. So, in a general way, we can say that the projection from the eye to the mid-brain is concerned with 'where' to look, while the cerebral cortex determines 'what' to look at.

The primary visual cortex is in the occipital region at the back of the head. Here the pattern of the retina is enormously enlarged, with 5000 cortical cells for each cell of the thalamus.

As signals from the retina pass through the various visual areas they are recombined in different ways. This is the process by which the words of the brain are joined in 'grammatical' ways to give meanings. No doubt, there are hereditary and karmic elements in the development of the grammar and it is also greatly influenced by experience.

In the later stages of decoding, each part of the system—retina, cells of the thalamus, the primary visual cortex - progressively extracts more and more abstract or general features of the visual information. The process does not continue uninterruptedly for vision, or any other sense. The whole set of brain actions goes on in discrete packages, each of perhaps one-fifth of a second. Our own awareness of the stream of consciousness suggests that there is some central processor receiving information at about this rate, which is also the order of frequency of the electroencephalogram.

At present, there is no adequate theory as to how the information from all sense-organs collected in the various cortical areas interacts to produce actions by us. It is likely that the 'putting together' of all the information is a property of groups of neurons. Anyhow it is a mistake to try to discover some 'final' stage of synthesis. Each part of the brain continually moves on from one action to another, just as the whole person does in real life.

D. Development of the Programs of Seeing

A three year old child shows few eye movements. There is very marked improvement upto 11 years as the scanning procedure becomes more systematic. As the speed and efficiency improves, movements are enough to allow the appropriate response. One can see this very well in the process of learning to read. At first, each letter must be examined separately, then words, phrases, sentences, whole paragraphs or perhaps pages or even whole books, can be in a sense 'comprehended' at a glance by a reader. The program for seeing probably consists of a routine that dictates a series of operations, guided by subroutines as expectations are examined.

E. Recovery of Sight

The most instructive of all the clinical studies of vision are those of patients who are born blind but have later recovered their sight after surgical operation. On recovery of vision, such patients are able to recognize only some of the objects that they already know by touch. They have, no program for seeing. With patience and time, they may learn to see, but it is a slow and painful process, unlike the normal acquisition of programs for seeing at the appropriate time of the developmental sequence of a child. This is an excellent example of one of the sensitive critical periods, when the brain is especially ready to develop some particular capacity. We have therefore a moderately clear idea of what we mean by programs for seeing. We shall discuss the programs of hearing in the next chapter together with those of speaking and writing.

Footnotes:
[1]
[2]
Share this page on:

Authors

Source/Info

Title: Neuroscience and Karma
Publisher:
Jain Vishwa Bharati, Ladnun, India
Editor: Muni Mahendra Kumar
Edition: Second Edition, 1994

Get this book at shop.herenow4u.net