Sleep psychologically considered : with reference to sensation and memory

Front matter

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W

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CHAPTER I. Sensation and Perception, 25

Phantasm, - - - - ■ 27

Reflex Action, - - - - - - - -31

Consensual or Associate Action, ----- 32

Mental Action, 34

Deranged Mental Action, ------ 37

Rapidity of Mental Action, 41

CHAPTER H.

Torpor, - - - 91

Introduction

The phenomena of sleep have engaged the speculative and philosophic consideration of psychologists from the earliest periods. And although deep-searching investigation has made no approximation toward the fundamental fact of what sleep is, still a vast store of knowledge has been accumulated, from which material may be drawn to define its operations, and determine the laws by which this condition of our being is governed.

The ultimate principles — or what sleep is, and what may be its cause — being, through Infinite wisdom, involved in obscurity so profound, that it can only be dissipated by disclosing the mysterious fountains of life, we pass to the consideration of its existence as a component of our mental and physical being. The phenomena of memory, as presented in connexion with sensation during sleep, will also engage our especial attention.

IS SLEEP PSYCHOLOGICALLY CONSIDERED.

We shall, in this Essay, endeavor to show, That during sleep, the mental faculties are as active as

during wakefulness ; That memory is no criterion by which to judge the

mind in sleep ; and That the mind is dependent upon the integrity of the

organs of external sensation for a remembrance of

what transpires during this state.

To establish these propositions, it becomes necessary to examine such of the pathological and normal phenomena of our compound being as bear relation to the subject. The mysterious as well as the more evident, the complex and the comparatively simple states in which our existence is involved, are made in some degree the subjects of our inquiry.

The doctrine, that the mind is as active during our sleep as when we are awake, has long been maintained by some physiologists. A writer upon dreams in the London Penny Cyclopaedia says, " It is a question, whether sleep operates on the mind as well as on the body ; whether while it suspends the action of the body, it also, either through the body or otherwise, suspends the action of the mind. This is a question on which we cannot speak positively, and on which our opinion can be determined" only by the greater probability of the one side or the other." That the greater proba-

INTRODUCTION. 19

bility is on the side of mental activity, we hope, in the course of our remarks, most fully.to establish.

Whether memory is dependent on the integrity of the organs of external relation, in the waking as well as in the sleeping state, may be questionable ; but many circumstances give plausibility to the suggestion that it may be. Do we remember anything not transmitted to the sensorium through the senses ? If not, any mental operation, independent of sensational organs for its primary stimulus, cannot be retained. When the mind is so riveted upon an idea, that these organs do not convey to the centre of perception external stimuli, there will be no recollection of things felt or seen, although they may have been-even powerfully impressed. The fact that memory is a faculty of the mind not fully comprehended, renders it a fit subject of speculation, and thus it may be as Dr. Reed says, " when philosophers have piled one supposition on another, as the giants piled the mountains in order to scale the heavens, it is all to no purpose — memory remains unaccountable ; and we know as little how we remember things past, as how we are conscious of the present."

In examining the phenomena of mind, with a view to establish the proposition, ' that the mind is dependent upon the integrity of the organs of external sensation, for a remembrance of what transpires during sleep/ it becomes necessary to present the psychological foundation upon which this conclusion is based. We should remark, however, that with the doctrine of essences, or ontology, we have little to do ; but that in the science of mind, in its more limited acceptation as regards its psycho-physiological phenomena, is to be found the sphere of our observations.

The mind, then, in the field of our labors, we regard as a unit, and as acting and being acted upon in one direction, through sensation, by external influences ; and in the other, by the innate powers of the organ of its own manifestation. The brain, notwithstanding the unity and immateriality of the mind, is so organized that particular parts are designed as fit instruments to reveal the properties of mind separately considered. The faculty of perception, the flow of feeling, and the power of thought, are elementary modes of organic activity by and through whose agency we know our position, exert our energy, and comprehend our relations. By a combination of these elements we are enabled to realize the outward world, and to grasp the results which arise from a contemplation of its phenomena. It is to this intermediate, this connecting link between the world of mind and the world of matter, that our philosophy is confined. How matter is so sublimated that the spirit principle is enabled to realize it, or how mind is so 'conjoined to matter as to be cog-

INTRODUCTION. 21

nisant of the operations connected with our material being, are problems to be solved, if ever solved, in the higher walks of metaphysical research.

External and internal sensations, and the powers of reflection, are the stimuli to these elementary principles or their special organs. Of these several sources of knowledge, we hold external sensation alone, as contributing to the permanency of our mental acquirements. It is at least doubtful whether the understanding or reason contributes any knowledge whatever. The facts acquired through sensation, are only combined and arranged by reason, and the results are brought into practical existence by the power of the will.

In the process of recollecting, the reflective faculty casts its stimulating influence through the mass of ideas already accumulated by observation, until it falls upon some one bearing relation to the subject in question, when, by association, that particular catenation is aroused, and in this manner the idea sought is quickly brought to view. This rationale having relation to ideas of outward existence alone, it may be asked, whether the mind has no power of recalling into mental being the memory of previous impressions from the vast field of the emotions ? We answer, it has not. It may create a new emotion, but cannot recall one which has passed. When by the power of recollection we bring to view pictures of material objects not then present to the senses, we merely bring up what was previously deposited in the mind ; the idea of the impression — not the impression itself; it is a re-presentation — not a creation. This is a memory of the fact : but through the reappearing of the idea, the feelings may be stimulated in their activity, and an emotion produced identical with the one caused by the impression on which the idea was originally formed, and which may again be incorporated in the mental process. This is not the memory of an idea, but the creation of an emotion. An organ of feeling has but one definite action ; and whenever excited, it is the creation of a new emotion, not the memory of one gone by. Its action can neither be induced nor varied by any direct intellectual effort, but may be indirectly stimulated through association with the perceptions, as it requires a repetition of the same stimulus to excite the emotion which originally induced it. In the re-excitement of an organ of internal sensation, we have its mode of action, which presents to the mind an actual existence — the thing itself. Memory is only a recall of ideas already formed — not a creation of them. On the contrary, when recollecting, the mind can re-assemble the ideas that originated in perception of material impressions, in proportion to the perfection of the ideas, and within the range of each

INTRODUCTION. 23

individual capacity. In this recall of ideas without reference to their origin, we recognise a distinct power of the mind, operating through the organs of perception, which we consider to be memory.

Memory, as before stated, is a mode of activity of the organs of perception stimulated by external sensation ; but recollection or voluntary memory, i. e. the power of recalling into thought the memory of past perceptions and their associate ideas, is an attribute distinct from what may be termed passive memory, or the mere remembrance of things unconnected with collateral circumstances. That volition may again and again bring up all these associations by an act of recollection, is undoubtedly true, for they have become the property of the mind, to be used as occasion may demand.

To distinguish consciousness from memory, we would say that the former does not depend upon the latter for existence, because consciousness is ever present, ever living. The consciousness of one period, and the consciousness of another, are connected by a variety of circumstances ; and it is an attribute of memory, through these circumstances, to combine these different periods of existence, making our lives one harmonious whole. When by disease the memory becomes impaired, it does not affect the consciousness. In such instances, the sources of memory, not consciousness, are involved. In many cases of insanity, the individual imagines himself to be another person ; and through impairment of memory, it is probable that identity, not consciousness, is lost : identity being the result of memory and consciousness combined. We are acquainted with a lunatic irrecoverably deranged, who believes himself to be the Lord Mayor of London, being originally from that city. But notwithstanding his imaginary social elevation, he knows himself; he answers to his name ; and in some particulars is aware of his actual condition. The chain of his identity is deranged and broken, but his consciousness is perfect, because it is a resistless, ever-present fact, like a full gushing fountain, springing unceasingly into existence.

Chapter I. Nervous And Mental Action

To sustain the views proposed in our introduction it becomes necessary briefly to treat of nervous and mental action, of association, and in some measure of deranged mental manifestation. It will be remembered, however, that only a cursory examination of these subjects will be made, and without special regard to systematic arrangement, because the subjects are treated of collaterally to the objects proposed.

Sensation and Perception.

For the mind to take cognisance of a fact or circumstance external to the body, an impression must first be made upon the nerve which produces a sensation ; the perception is then awakened, and consciousness is the result. Should attention be directed to the perception, it then becomes the subject of intellectual operation, ideas are formed, and memory records the fact or circumstance.

Every perception of external relation creates an idea in the mind which becomes memory, and under 2 proper circumstances can be recalled and compared with other perceptions present* Muller says, " we know that every idea is a permanent, immutable impression in the brain, which may at any moment present itself anew if the mind be directed to it — if the '■ attention' be turned to it, and that it is merely the impossibility of the attention being occupied by many objects simultaneously that causes each to be forgotten. All these latent ideas must be regarded as impressions on the brain which cannot be effaced. Lesions of the brain may annul a part or all of these ideas."

Impressions upon the sensitive nerves are transmitted in either a peripheral or centripetal direction, according to the part impressed. If upon the root or trunk, it is perceived at its extremity ; if upon the fibrils, the impression is transmitted to the nervous centre. An injury to the body of the ulnar nerve at the elbow is referred to the extremity or the nervous fibrils of the little finger, and is a familiar instance in point. It is a well known fact, that persons having lost their limbs, dream of sensations in the excised parts as vividly as though the members were in situ. The cause is either from an internal mental impression, or from an external mechanical irritation, as by pressure upon the nervous trunk.

AND MENTAL ACTION. 27

Phantasm.

The reception of sensational impressions is, according to Muller, a mode of action of the sensational nerve. This corresponds with Combe's idea of certain properties of mental organs being a mode of activity with them.

When a sensational organ is excited, either byinternal or external influences, the effect on the mind will be identical. The nerves of sensation stand, as it were, between the external impression and the internal idea. The retina, for instance, can be, in very many cases, excited as vividly by the inward influence as by the outward producing phantasm. To the mind, in such cases, facts only are presented, and to the organs of sense, ideas.

There appears to be a nervous mode of action existing between the external impression and internal perception, having relation, on one hand, to the mind, and on the other, to the sensitive nervous extremities. When this mode is excited by an internal idea with sufficient intensity, the organ, as of vision, is thrown into its mode of action ; it actually sees the idea, returning it as a simple impression to the mind, and if this condition is not corrected by other mental powers, there is partial alienation. Should the action occur in sleep, a dream of the most vivid character will be induced. The idea is, as it were, reflected upon the sensational apparatus, exciting in it actual impressions, as observed by Spinosa, and attested by Muller, that images seen in dreams are sometimes still visible, and can be observed to disappear gradually to the waking eyes. Dreams that present us with the most vivid conceptions are those in which phantasms are produced. The internal excitement having operated upon the organs of sense, to produce the same result that corresponding external stimulus would have done, the memorial power is aroused the same as though we had actually seen, or heard, or felt the impression.

Muller, in reviewing the phenomena of phantasm, says, " The facts already mentioned prove that the images seen in dreams, not the mere ideas of things conceived in dreams, are phenomena of the same kind as the phantasms. For the images which remain before the eyes when we awake are identical with the objects perceived in our dreams."

In the latter part of the eighteenth century, a Prussian bookseller named Nicolai, gave the most remarkable account of phantasm, which occurred in his own case, to be found on record. He says, " I saw, in a state of mind completely sound, and — after the first terror was over — with perfect calmness, for nearly two months, almost constantly and involuntarily, a vast number of human and other forms, and even heard their voices, though all this was merely the consequence of a diseased state of the nerves, and an irregular circulation of the blood. When I shut my eyes these phantasms would sometimes vanish entirely, though there were instances when I beheld them with my eyes closed ; yet, when they disappeared on such occasions, they generally returned when I opened my eyes. I conversed sometimes with my physician and my wife on the phantasms which at the moment surrounded me ; they appeared more frequently walking than at rest ; nor were they constantly present. They frequently did not come for some time, but always reappeared for a longer or shorter period, either singly or in company ; the latter, however, being most frequently the case. I generally saw human forms of both sexes, but they usually seemed not to take the smallest notice of each other, moving as in a marketplace, where all are eager to press through the crowd ; at times, however, they seemed to be transacting business with each other. I also saw, several times, people on horseback, dogs, and birds. All these phantasms appeared to me in their natural size, and as distinct as if alive, exhibiting different shades of carnation in their uncovered parts, as well as in different colors and fashions in their dresses, though the colors seemed somewhat paler than in real nature ; none of the figures appeared particularly terrible, comical, or disgusting, most of them being of an indifferent shape, and some presenting a pleasing aspect."

Goethe, the celebrated German poet, possessed the rare faculty of producing phantasms at will. < He says, " When I close my eyes and depress my head, I could cause the image of a flower to appear in the middle of the field of vision ; this flower did not for a moment retain its first form, but unfolded itself, and developed from its interior new flowers, formed of colored or sometimes green leaves. These were not natural flowers, but of fantastic forms, although symmetrical as the rosettes of sculptors. I was unable to fix any one form, but the development of new flowers continued as long as I desired it, without any variation in the rapidity of the changes. The same thing occurred when I figured to myself a variegated disk. The colored figures upon it underwent constant changes, which extended progressively from the centre towards the periphery, exactly like the changes in the modern kaleidoscope."

In both these cases the objects were as actually seen by the visual apparatus as though they had been externally presented to the organ of vision. Through the central excitement the retina was thrown into its mode of action by the idea, and returned to the brain the phantasm as a simple fact.

Reflex Action.

Another mode of nervous action, but having less dependence on the brain than those just considered, is termed reflex. This action is a peculiar function of the spinal cord, and prolongs the natural movements of muscles associated for certain definite purposes, as of locomotion ; and when they are once set in operation, do, by so slight a degree of sensation that it makes no impression on the sensorium commune, continue to operate in the direction of the impulse, until changed by a mandate of the will, or arrested by physical obstruction.

A good example of reflex and associate action occurs in the act of swallowing. When a morsel of food is carried so far back in the mouth as to impress the sensitive nerves of the fauces, the muscles of deglutition are immediately aroused, and not only act independently of the will, but they require its strongest effort to resist their movement if desired.

Now, such action being independent of volition, it may, when once called into play, be continued by causes that do not affect the brain ; and, consequently, when a consecutive train of action is started, it may be prolonged independently of the will. This state may occur as well during sleep as in vigilance, for we know that the action of the muscles of organic life is maintained in sleep by this process ; the blood is propelled by the heart, and respiration by the associate action of the muscles of the chest.

The medulla oblongata is the seat of sensation and reflex action. Without the cerebrum animals will fly and walk, and yet appear as though asleep. Among the experiments of M. Flourens, we find that " an animal, in which the cerebral hemispheres have been removed, is in a state of stupor, but presents, nevertheless, manifest signs of sensibility, and not merely of the reflection of impressions. It no longer performs any voluntary movements, but, when struck, it has all the manner of an animal waking from sleep. In whatever position it be placed it resumes the equilibrium. If laid upon the back, it rises again ; if pushed, it walks. If it be a bird, and we throw it up into the air, it flies ; if it be a frog, it leaps when touched. The animal has, doubtless, lost its memory, it no longer reasons ; but, nevertheless, it feels, and the sensations excite in it movements which are different from the phenomena of mere nervous reflection. Cuvier very aptly compares animals in this condition to a sleeping man ; he also seeks an easy position — he feels."

Consensual or Associate Action.

Consensual or associate muscular action consists in the contraction of a single muscle of a particular set being followed by a determinate movement of the others, independent of, and oftentimes contrary to the will : one eye, for instance, cannot be changed in its axis without being followed in the same direction by the other. The following experiments illustrate this mode of action. The first movement of the series is perforce produced, and the associate movements follow in consequence. " In a pigeon," M. Flourens " removed both cerebral hemispheres ; loss of vision immediately ensued, with general loss of power, which, however, was neither considerable nor persistent. The pigeon flew when it was thrown into the air ; walked when it was pushed. The iris had its power of motion in both eyes ; the animal was deaf, and it did not move spontaneously, but had constantly the manner of a sleeping animal, and, when irritated, it resembled in its motions an animal just awaking. In whatever position it was placed, it resumed its equilibrium ; if laid upon the back, it got upon its feet again ; water being put into its beak, it swallowed it ; and it resisted attempts to open its beak." " He likens the pigeon in this condition to an animal condemned to perpetual sleep, but without the faculty of dreaming."* " M. Hertwig removed the upper part of the hemispheres in a pigeon ; sight and hearing were

* Mullens Physiology. 2* abolished, and the animal sat in one spot as if asleep. He fed it : peas, if placed merely within the beak, were not swallowed ; but if laid upon the tongue, they were (owing to reflex action) ; the muscles were but slightly enfeebled ; the bird stood firmly, and flew when thrown into the air. This state endured for a fortnight, when the hearing and sensibility in a great measure returned ; this pigeon lived three months." " A hen, in which he had cut off both hemispheres nearly to the base of the brain, was found to be deprived of sight, hearing, taste, and smell ; it sat constantly in one spot, and was as if dead until strongly roused, when it moved a few steps. The animal lived in this state of stupor, without its senses being restored, for three months."*

Mental Action.

Mental action does not consist of light, or sound, or touch ; for none of these existences reach the brain : but of ideas originating from the stimulus of perception acting upon the mental organ. Out of ideas thus created, the mind forms its images of fancy in harmony with the leading or originating idea, modified by individual temperament. Thus the idea excited by music may associate in the mental process, the sombre

* Muller's Physiology.

light of a cathedral, the brilliant dazzle of the assembly, or the red volcanic fires of the battle-field — not merely as the strain may vary, but in harmony with the individual mental character.

We seldom enjoy the delights arising from the gratification of one sense, without ideas peculiar to others being excited in the mind. This excitement is awakened by arousing the memory, which at once combines and associates the whole to produce the mental result.

Ideas depend in a great degree for their perfection upon the integrity of the senses, because the mind can have no conception of light, for example, unless memory can recall its influence ; and where the organ of vision never existed, there is nothing of this influence to be associated in the mental operations, and so it is with all the other special sensations.

The deaf do not dream of sounds, nor the blind of sights, when deafness and blindness are congenital. Where a sense has never existed there can be no idea of its phenomena in the mind, and of consequence there can be no memory regarding it. The most lucid mental perceptions we experience, and those the longest retained, arise from direct impressions upon the organs of sense. To illustrate — we might have the colors and form of the rainbow described by the most profound philosopher that ever existed, and couched in

3b SLEEP PSYCHOLOGICALLY CONSIDERED.

the language of an exuberant imagination ; and we might have often seen its primary colors, and be perfectly familiar with the form of the arch ; yet its gorgeous glow and sublime proportions as it appears in the heavens, would be faintly portrayed to the mind ; the whole conception would arise from an intellectual operation, without the foundation upon which an idea can permanently rest, and there would be very little to place in the storehouse of memory : but let the organ of vision once take an impression of the bow of promise, and the idea springs from a source that will last as long as the integrity of the mind endures.

When intellectual operations depend upon internal impressions for their stimulus, as during sound sleep, they are deprived of the imperishable quality imparted by external sense ; but when they occur during the stages of slumber or dreaming, they are remembered just in proportion to the susceptibility of the senses providing stimulus of action.

Dr. George Moore says : " The action and reaction between mind and body are incessant, since there is not a moment, either in our waking or sleeping experience, when the nerves are not agitated by ideas." And Dr. Dendy says, that " mind is not the product of organization, but it works by and through it ; and therefore for its earthly uses, cannot be independent of the qualities of matter." Although matter has its influence upon mind, still the mental reaction is such as to control its special organ, the brain, and even to exert an extraordinary influence upon the whole animal economy. If the mind is immaterial, it is necessarily divested of inertness, the distinguishing quality of matter, and must therefore be altogether absent from the body during sleep, or its organ must be in ceaseless activity. The mind being immaterial, both it and its immediate organ are absolutely sleepless.

This idea is beautifully expressed in the following stanza. Poetry has its philosophy, and we often find the imagery of the poet imbued with the severest reason :

" Though thy slumber may be deep, Yet thy spirit shall not sleep ; There are shades which will not vanish, There are thoughts thou canst not banish."

Deranged Mental Operation.

Deranged mental operations depend more upon an exalted condition of the propensities and sentiments, than upon external appliances. When the mind is thus excited, impressions received through the external senses seem to impair the perception so much, that it conveys to the reflective powers so little of objective reality, that they are left to regulate their own operations by the internal workings of diseased organs.

Actions flowing from such a state of mind, stamp upon the individual the character of insanity.

Now in what does such a state of mind differ from that of sound sleep? It differs in the circumstance, that external relation is by sleep withheld from the reflective faculties merely, while sleep continues, and the organs of feeling are in a healthy condition, but for a limited period permitted, as it were, to run at will, free from the restraints of rigid reason.

Insane persons appear to be only momentarily influenced in their mental manifestations by physical pain ; but in sleep, it is a common cause of a connected train of thought during a long dream. Dr. Gregory, having applied a bottle of hot water to his feet, dreamed that he made the ascent of Mount vEtna; and a blister applied to the nape of the neck caused the patient to dream of being scalped by Indians. From the circumstance that the thoughts of the insane are excited more by internal than external sensations, we should conclude that the memory of a diseased is less active than of a healthy brain.

Between dreaming and insanity, there is a singular resemblance. The brain, when diseased, does, through its exalted internal sensations, excite in the waking mind the same irregularity of ideas which arise in dreams when the regulating power — the external senses — is withheld. In hallucination the external is overpowered by the internal stimulus, but not obliterated.

The hallucination of Tasso, as related by Manso, Marquis of Villa, will illustrate this position : " Tasso in his delirium believed that he conversed with familiar spirits. One day, when the Marquis endeavored to drive these ideas from his mind, Tasso said to him, ' Since I cannot convince you by reason, I shall do so by experience ; I shall cause the spirit, in which you refuse to believe, to appear to your own eyes.' I accepted the offer, says the Marquis, and next day, when we sat by the fire conversing, he turned his eyes towards the window, and looking with steadfast attention, appeared so completely absorbed, that when I called to him, he did not answer. ' See !' said he, at length, ' See ! my familiar spirit comes to converse with me.' I looked with the greatest earnestness, but could see nothing enter the apartment. In the meantime, Tasso began to converse with this mysterious being. I saw and heard himself alone. Sometimes he questioned, and sometimes answered ; and from his answers, I gathered the sense of what he had heard. The subject of his discourse was so elevated, and the expressions so sublime, that I felt myself in a kind of ecstasy. I did not venture to interrupt him, nor to trouble him with questions, and a considerable time elapsed before the spirit disappeared. I was informed of its departure by Tasso, who, turning towards me, said, * In future you will cease to doubt.' ' Rather,' said I, 'I shall be more sceptical, for although I have heard astonishing words, I have seen nothing.' Smiling, he replied, ' You have perhaps heard or seen more than .' He stopped short ; and, fearing to importune him by my questions, I dropped the conversation." Tasso was awake ; but having a diseased mental organ, he was insane ; his external senses were intact, but the intellectual being received impressions from disordered organs of internal sensations ; and the objects presented to his mind were paramount to the words of Manso. He did not acknowledge external stimuli, because his mind was too much absorbed with the delusion. Here, also, a dissimilarity, as well as resemblance between dreaming and insanity, is clearly observable. In sound sleep, when the sensational organs are inactive, mental occurrences are not remembered. In this case, though Tasso did not acknowledge a perception of realities, and was occupied entirely by creations of his own fancy, still, the nerves of sense were perfect, and had an influence ; a remembrance of what passed in his mind was retained from one paroxysm to another. " The subject of the discourse," said Manso, " was so elevated, and the expressions so sublime, that I felt myself in a kind of ecstasy." Such elevation and sublimity are to be obtained under circumstances of mental abstraction to a degree only found in dreaming, or in the operations of a diseased brain.