Bodily responses

The peripheral nervous system

The peripheral nervous system is composed of two sub-systems: the autonomic system and the somatic system. The somatic system carries messages to and from the sense receptors, muscles and the surface of the body. It is this system that makes us aware of pain, pressure and temperature changes. The nerves of the somatic system also carry all involuntary movements of muscles that deal with balance and posture. In other words, the somatic system relays information to the brain about the body in relation to the environment in which if finds itself.

The second main element of the peripheral nervous system is the autonomic nervous system. However, this acts together with the neuroendocrine system. The autonomic nervous system, it should be appreciated, is called this for historical reasons. In the history of anatomy, the autonomic nervous system was so called because it was considered to be automatic – and as such outside conscious control. However, because it is part of the nervous system that establishes a unity, then it can be brought under conscious control to some degree by the central nervous system. The autonomic nervous system consists of the nerves that connect internal organs to the central nervous system and regulate especially glands, respiration, heart rate and digestion. Furthermore, the autonomic nervous system plays a major role in emotion.

Although the autonomic nervous system is not essential for life, in the sense that large portions can be removed with only little functional impairment, when an organism is exposed to stressful situations then any absences can lead to mal-adaptive behaviour. The reason for this is not hard to see. The essential function of the autonomic nervous system is to modulate the activity of its target organs so that they respond appropriately to changing external environmental conditions. If this modulation either cannot be performed, or can only be partially performed, then the response does not occur or only partially occurs or is not a suitable response.

The autonomic nervous system is divided into two parts: the sympathetic and the parasympathetic nervous systems. The system as a whole controls the glands and the smooth muscles that is to say the muscles of the heart, blood vessels and the stomach (as distinct from those muscles connected to the skeleton). The sympathetic nervous system is composed of two main chains of nerves on either side of the spinal column from which connections are made to various organs in the chest, stomach, and lower abdomen. The parasympathetic nervous system is composed largely of two parts. One part has nerve fibres arising from the upper part of the brain stem and a second part has nerves emanating from the lower region of the brain stem. About eighty percent or more of the parasympathetic nerve fibres are in the upper portion that passes to the chest and stomach.

In appreciating the different roles of the sympathetic and parasympathetic nervous systems it is important to realise that the sympathetic nervous system is initiated by changes which are detected as going on in the external environment. On the other hand, the parasympathetic nervous system is activated by changes that are detected as going on in the internal environment, a distinction of importance for hypnosis.

There are some significant morphological differences between the sympathetic and the parasympathetic nervous systems, but from our point of view one of the major differences is the fact that the ganglia of the sympathetic nervous system are located away from their target receptors and, on the contrary, are often located parallel to the spinal cord, as indicated above. The result is that the postganglionic axons of the sympathetic nervous system are quite long. Furthermore, because of the long postganglionic axon, cells of the sympathetic nervous stem tend to receive information from several different layers of the spinal cord. The importance of this is that the activity of the sympathetic nervous system will not be confined to a single organ but, on the contrary, will have widespread effects. It produces high levels of arousal and prepares the organism for ‘fight-or-flight’ (see BOX 1). In particular, high stress situations require the simultaneous and coordinated responses of many different visceral muscles and glands.

BOX 1 Fight-or-flight response and relaxation response

The ‘fight-or-flight’ response is well known and well documented but its opposite, the ‘relaxation response’ appears far less well known and less well understood. In this box we shall consider both responses together, concentrating particularly on the physiological aspects, and referring to them as the ‘stress response’ and the ‘relaxation response’ respectively.

Under the stress response there is typically an increase in blood pressure, heart rate and breathing; an increased blood flow to the muscles; and an increase in body metabolism. All these reactions prepare us to either fight or escape. Today, however, the stress response is not just brought on by imminent danger but most commonly by a need for some sudden behavioural adjustment. This has two important implications. First, it is brought on under many and varied circumstances. Second, the physiological changes that are associated with it tend not to be neutralized, and so the cumulated stresses can lead to extreme problems of heart attacks and strokes.

Benson (The Relaxation Response, 1975) argues just as there is a stress response that switches on appropriate bodily responses, so there is a relaxation response that switches off these same bodily responses. It is typically opposite that of the stress response and reduces blood pressure, heart rate and breathing; reduces blood flow to the muscles; and decreases body metabolism. Although the stress response is readily switched on (being instinctive) by everyday needs of behaviour adjustment, the same is not true of the relaxation response. It appears that we need to learn the relaxation response and apply it consciously.

Benson argues that the relaxation response has always existed and is well known in Eastern cultures, and in some Western religious practices. A main part of the work undertaken by Benson and his team has been to develop techniques for eliciting the relaxation response. He summarizes them as follows:

Place yourself in a quiet environment
Repeat a word or phrase over and over again
Adopt a passive attitude
Adopt a comfortable position

Of these, he rates the third as the most important. However, these same conditions are required for hypnotic induction.

But what initiates the stress response? It is the hypothalamus, which lies at the centre of the brain. If the hypothalamus is repeatedly activating the stress response, then a higher blood pressure becomes the norm and the individual develops permanent hypertension.

When the stress response is turned on the sympathetic nervous system is activated. As part of this reaction there is an increased secretion of specific hormones - namely, adrenalin (epinephrine) and noradrenaline (norepinephrine). It is the secretion of epinephrine that leads to increased blood pressure, heart rate and body metabolism. More important is that all body responses occur in a coordinated fashion and simultaneously, being orchestrated by the hypothalamus. The relaxation response quietens the sympathetic nervous system according to Benson. It signals a reduction in the production of epinephrine and norepinephrine and so reduces blood pressure. What is not mentioned by Benson, which is somewhat surprising, is any effect the relaxation response has on the parasympathetic nervous system.

The work on biofeedback convincingly demonstrates that man can control his autonomic nervous system: that he can control his involuntary responses. But such control over the autonomic nervous system had been recognised, accepted and utilized by Eastern meditation techniques for centuries. Biofeedback experiments only provided scientific evidence of such control to the satisfaction of Western scientists. It was in investigating the responses of Transcendental Meditation (TM) that researches realized that the responses they were observing were part of an integrated response that was opposite to that of the stress response. They also realized that this response was not unique to TM. Certainly what the responses were showing was a decrease in the activity of the sympathetic nervous system.

The coordinated responses of the relaxation response had been demonstrated to be a result of the hypothalamus, where a different part is active from that which elicits the stress response. This was demonstrated by Walter Hess and his work on the brain of cats, in which he stimulated different parts of the hypothalamus. It appears reasonable that both the stress response and the relaxation response should be under the control of the same organ. But a number of techniques appear to elicit the same physiological changes as the relaxation response, of which hypnosis is just one.

On the other hand, the parasympathetic ganglia are located close to the peripheral parasympathetic receptors, and as such they have short postganglionic axons that spread into the particular organ. Neural connections, therefore, within the parasympathetic nervous system are quite specific. This means that parasympathetic activity tends to be specific – although this should not be taken too far. There is some association between various parasympathetic responses. For example, salivary, gastric and pancreatic secretions often occur together. However, these are limited in comparison with the sympathetic nervous system.

Although something of an over-exaggeration, it is possible to think of the two systems as influencing the body in opposite ways. When each system is stimulated the result is to excite some organs and to have inhibitory effects on others. More significantly, when sympathetic stimulation tends to excite a particular organ, parasympathetic stimulation tends to inhibit it. It is the case, however, that most organs are largely controlled by one or other of the two systems and so, in general, the two systems do not oppose each other. But even this is too simplistic. In a number of cases the two systems act together, and in still other cases they act in sequence. The interrelationship between the sympathetic and the parasympathetic nervous system is not yet fully understood. What have been established are the effects on various organs of excitation of each of the systems.

The sympathetic nervous system will, when a person is emotionally excited, bring about an increase in heart rate, dilation of the arteries of the muscles of the heart, constriction of the arteries of the skin and digestive organs, so leading to perspiration and the increase in emotional arousal. On the other hand, when the parasympathetic nervous system is aroused the pupils contract, the heart rate slows down, breathing slows down (as constriction of the bronchi takes place) and the skin dilates.

The sympathetic and parasympathetic nervous systems and hypnosis

So far we have been fairly factual in our account and have made little reference to hypnosis. Now let me turn to some conjectures in the light of the discussion so far. It must be emphasized, however, that these are conjectures on the part of the author.

In the history of hypnosis we noted the difference of opinion between the Salpêtrière and the Nancy School . The work at the Salpêtrière was on schizophrenics. Such subjects are usually emotionally aroused, can create catatonic states, and show general hysterical symptoms associated with a highly activated sympathetic nervous system. When the sympathetic nervous system is very aroused the body takes on a ‘fight-or-flight’ condition (see BOX 1). Action is almost reflexive and spontaneous. This is not surprising from the remarks we have made above. The postganglionic axon run parallel and close to the spinal cord, and it is within the spinal cord that the reflex arc is formed, bypassing the brain and giving rise to immediate action. In other words, when the sympathetic nervous system is highly aroused, conscious thought processes are largely bypassed. But this is one of the main requirements for inducing hypnosis, although by no means the only one.

The induction of hypnosis by Mesmer under the name of animal magnetism had all the same features. His dramatic entry, his arrangement of individuals in a circle with men and women alternating, his requirement of their thighs touching to increase the flow of magnetism, etc, all lead to an aroused sympathetic nervous system. On top of this was an expectation that things would happen. This expectation was based partly on what Mesmer himself expected and partly on what the patients expected they should do (no doubt having heard what others had done).

It should be recalled from our earlier discussion that the sympathetic nervous system is initiated by changes which are going on in the external environment. The induction of hypnosis at the Salpêtrière and by Mesmer was clearly part of the external environment and as such the patient was responding to this.

On the other hand, the Nancy School followed the procedures laid down by Braid. His method involved quiet repose and slow breathing, amongst other things. But it should be clear from our discussions that what Braid’s method is doing is to activate the parasympathetic nervous system. It is an activation of the ‘relaxation response’ outlined in BOX 1 . Although the Nancy School involved suggestion, what the suggestion was doing was getting the individual to relax and to direct the patient’s attention to the internal workings of their body. Their breathing, their heart beat, and so on. But again it is important to note that the parasympathetic nervous system is activated by changes that are detected as going on in the internal environment. But getting the patient to concentrate on their breathing or their heartbeat is important from another point of view in terms of the way the parasympathetic nervous system works. We made the point that the parasympathetic nervous system acts far more specifically than the sympathetic nervous system (with its much smaller postganglionic axons). We also made the point that it mainly affects the chest and stomach. Concentration on slow rhythmic breathing or on the heartbeat will, therefore, activate the parasympathetic nervous system.

Activation of the sympathetic nervous system means that the reflex arc comes into action, which is why the brain is bypassed, and why suggestions made in this state are often not consciously processed. But what is the equivalent within the parasympathetic nervous system? There is no equivalent to the reflex arc in the spinal cord! There is no point because the nerves of the parasympathetic nervous system operate more specifically. However, as more areas of the parasympathetic nervous system become active and the body relaxes and the brain begins to monitor more explicitly the body’s internal state, so it pays less attention to suggestions made to it. As we shall note shortly, what happens is that as the parasympathetic nervous system becomes more activated so there is less need for the brain to bring the cortex into action – and it is the active cortex that inhibits hypnotic induction. What seems to be happening, therefore, is that when the parasympathetic nervous system is activated then it also appears to be the case that the conscious mind is bypassed. Once the conscious mind is bypassed, suggestions will be responded to more directly.

What is clear from our discussion so far, however, is that the induction of hypnosis undertaken by activating the parasympathetic nervous system is likely to be much slower than activating the sympathetic nervous system. This should not be surprising from our analysis. The sympathetic nervous system works on many parts of the body simultaneously while the parasympathetic nervous system is much more selective. The sympathetic nervous system utilizes the body’s natural reflex while there is no equivalent for the parasympathetic nervous system.

Negative and positive hypnosis

Here we shall define negative hypnosis as suggestions made in the context in which the sympathetic nervous system is very active; and define positive hypnosis as suggestions made in the context in which the parasympathetic nervous system is very active. This distinction illustrates that what matters in hypnotic induction is not the suggestions per se, but rather the context in which the suggestions are made. More specifically, whether the suggestions are made while the sympathetic nervous system is aroused (negative hypnosis) or whether the suggestions are made when the parasympathetic nervous system is aroused (positive hypnosis). It should be noted here that it does not matter what the suggestion is, it can have the same effect regardless of which nervous system is activated. What may differ, however, is how long lasting the effect of the suggestion is. But we shall return to this later.

The divided brain

The cerebral cortex is divided into two halves, called the left and right hemispheres. Although they appear as symmetrical structures modern research has shown that there is a difference in function. This asymmetrical nature of the brain is referred to as cerebral dominance. The functional differences between the two halves have a great deal to do with a person’s psychological functions, although not only these.

The left hemisphere of the brain controls the right side of the body, while the right hemisphere controls the left side of the body. More important from our present point of view is the type of function for which each hemisphere is responsible. Although there are no hard and fast rules, in general, there is a pattern of specialization that is fairly common. This is indicated in figure1.

Figure 1

It is clear from figure 1 that what we commonly think of as ‘conscious thought’ takes place largely (although not wholly) in the left hemisphere; while many functions we commonly think of as ‘unconscious thought’ take place largely (although not wholly) in the right hemisphere.

The simplest way of thinking about the specialization of the brain is to consider the brain’s process while you are talking to someone. Your left brain is picking up what they are saying and processing the information and then activating your speech centres for your reply. At the same time, your right brain is considering the other person’s facial expressions, their mannerisms, the intonation in their voice, etc. In other words, the left brain is processing verbal cues while the right brain is processing nonverbal cues. Now if the two halves could not communicate with one another this would not be a sensible procedure. But information taken in by one hemisphere is passed to the other by means of the corpus callosum. It is this sharing of information that gives us a sense of unity: of oneness. The verbal and nonverbal incoming information can either be in agreement or can be conflicting.

But what has just been said indicates that one hemisphere dominates for a particular function. But it is not as simple as this. If you wish to pick up a cup you can do it with either hand. You do not find yourself in conflict or indecision. The fact that you pick up the cup without hesitation means that one hemisphere of the brain has taken a dominant role for this act. It would appear that this is a function of the corpus callosum. For any act only one hemisphere is dominant. It would also appear that hemispherical dominance switches throughout the day. To observe this, try exercise #1.

Exercise #1 Nostril test

Throughout a particular day or half-day, notice which nostril you breathe through the most. Although you can take in air through both nostrils, one will be the dominant one. To check this, press your finger on the side of the nose to block one nostril. Then do the same with the other. Which is easier to breathe through? Check this out at different times and note which nostril is easier to breathe through. When it is easier to breathe out of the right nostril, the left hemisphere is dominant; when easier to breathe out of the left nostril, then the right hemisphere is dominant.

What this present research indicates is that the function of the right hemisphere is very under-rated. Part of the reason for this view was that if the right hemisphere became damaged it did not appear to impair the individual as much as when the left hemisphere became damaged. However, we now know that the right hemisphere has its functions spread over a greater area of the brain tissue than does the functions in the left hemisphere.

For the hypnotist and self-hypnotist, knowledge of the hemispherical specialization of the brain gives him or her insight into the hypnotic state itself. The induction procedure, whether self-induced or induced by someone else, activates the parasympathetic nervous system. Since conscious control appears to be given only to one hemisphere at a time, then it could be argued that the induction procedure is a method of giving the dominance to the right hemisphere of the brain. By closing the eyes and reducing sensory input, and also by means of suggestion, the ‘alert’ mechanism is not activating the left hemisphere of the brain. The left hemisphere of the brain is being used less because the induction procedure does not require logical thinking. A number of the suggestions involve imagery, such as being warm and comfortable while lying on a beach. Such images are specifically directed at activating the right hemisphere of the brain where such imagery is largely (although not wholly) processed. It would appear, although this is only conjecture, that less information traverses the corpus callosum. When this is achieved, as it is in hypnosis and other altered states of consciousness, the nervous system responds to the suggestions as if they were true. If the induction procedure of hypnosis is successful then the left hemisphere will not check incoming suggestions against reality – that is, reality testing will not take place – as this is a left brain function. If no reality testing takes place, then as far as the nervous system is concerned the information contained in the suggestions is correct and the body will respond to it accordingly. The ‘closing down’ of the left hemisphere is also shown by the subject’s change of speech. This becomes slow and difficult during the induction phase. This is consistent with a reduction of cortical activity in the left hemisphere of the brain.

The process just described is not simply a question of hemispherical specialization. We have made the point that the brain is composed of three interrelated structures. All three structures are probably involved in this procedure. For instance, the repetitive phrases of the induction procedure lead to habituation, which is part of the limbic system. The conjecture being advanced here is that hypnosis involves the establishment of a particular relationship between the different parts of the brain, and it is sufficiently distinct from other configurations, such as being awake or being asleep. To highlight this point in relation to hypnosis we present in BOX 2 an experiment undertaken by Dr John Gruzelier at London ’s Charing Cross Hospital Medical School . This study, besides shedding some interesting light on the hypnotic process, suggests that hypnosis should not be taken to be a feature only of the right hemisphere, but is to do with a particular configuration of right and left hemispheres.

BOX 2 An experiment on hypnosis and hemispherical specialization
From the New Scientist ‘Hypnosis relies on left brain dominance’, 2 August, 1984.

Interest in the connection between hemispherical specialization of the brain and hypnosis has led to some interesting studies. One is that undertaken at London 's Charing Cross Hospital Medical School under Dr John Gruzelier of the psychiatry department. In this research they were studying people's electrical skin conductance during hypnotic induction. Electrodermal response is generally considered an indication of how much attention a person is paying to a particular stimulus or stimuli. The experiment involved running a hypnotic induction tape for seven minutes during which time subjects were also played a number of one-second seventy-decibel tonnes at regular intervals. Dr Gruzelier explains the basis of his approach as follows:

... to achieve effective induction, one has to narrow one's attention to what the hypnotist is saying and a susceptible subject will be the person who can best focus his attention initially.

The aim of the tones, therefore, is to distract the individual from concentrating on the hypnotic induction tape. The article continues,

Before induction, the people who subsequently proved susceptible to hypnosis had greater electrodermal responses in their left than in their right hand. The opposite was true of unsusceptible individuals. As the induction tape was played, this asymmetry was reversed in susceptible people, the right hand responses becoming the larger. But no such effect was seen when unsusceptible subjects were played the same induction tape.

Because of the know association between electrodermal activity and brain hemispheres, it seems that susceptible individuals start off with the left side of their brain holding sway and then, under induction, switch over to the right side. The susceptible people also habituate faster to the intrusive tones - they showed fewer electrodermal responses - suggesting they were able to ignore them.

The hypnotic state seems to be associated with the right hemisphere of the brain [according to Dr Gruzelier and his team]; its dream-like quality, altered time sense, attitude of passive acceptance and several other characteristics all suggest this. And under hypnosis this was confirmed in that the susceptible subjects did switch into a right hemisphere 'mode'.

Dr Gruzelier points out that what matters is the left brain dominance of those who are susceptible but who can switch to right brain dominance during the hypnosis. The left brain dominance during induction is important in order for the individual to ‘focus their attention’. Unsusceptible subjects, however, start with right brain dominance, with its associated ‘broadened attention’ such that they cannot concentrate sufficiently on the induction even to begin to be hypnotized.

Studies such as this shed considerable light on the hypnotic process. It also suggests that a simple statement that hypnosis is all to do with the right brain is probably incorrect.