Sleep

SONNO. — Sleep, from a biological point of view, appears as an aspect of a phenomenon common to all living beings, in both the animal and plant kingdoms, which undergo alternations of activity and rest. Houssay defines it as a necessary, restorative, normally periodic and reversible physiological state, characterized by a depression of sensitivity, consciousness, and spontaneous motility, and above all of muscle tone, without any significant decrease in basal metabolism or appreciable slowing of vegetative functions.

I. PHYSIOPATHOLOGY OF SLEEP

The transition from wakefulness to sleep is normally progressive and is announced by a feeling of fatigue, heaviness, and lassitude, by a lack of interest in what is happening around us, and by difficulty in keeping the eyes open; it occurs after an alternation of phases of attention and inattention, during which hypnagogic hallucinations take place, represented by disconnected, momentary images that undergo rapid metamorphoses and disappear when the eyes are opened or moved.

During sleep, relaxation of the entire musculature predominates, except for the masseters, the orbicularis muscles of the eyelids, the sphincters, and the clenched fist in the child. The pupils are constricted and the eyeballs are rotated upward and outward. The number of heartbeats decreases by 10–30 per minute and arterial pressure by 10–20 millimetres of mercury. The number of respiratory excursions also decreases, with a long and noisy inspiratory phase and a rapid expiratory phase. Basal metabolism falls by 10–15% during deep sleep, and body temperature drops by a few tenths of a degree. Sweat secretion increases during deep sleep, and the urine is less abundant but dense, acid, and richer in phosphates. Gastric function undergoes no notable changes. Cerebral activity is reduced but not abolished. In the electroencephalogram, all rapid waves disappear during deep sleep, and only very slow waves persist. The average duration of physiological sleep varies according to age, constitution, occupations, and season; in general, a newborn sleeps 20 hours a day, and a child from one to seven years old sleeps from 10 to 14 hours; an adult sleeps from 7 to 9 hours, and an elderly person from 5 to 6 hours. Sleep is an indispensable need of the organism. Some experimenters, including Kleitman, have observed that after 80–115 hours of insomnia the persons they studied presented mild psychic disturbances; it has nevertheless been found that prolonged insomnia lasting ten days causes death in humans when other kinds of suffering coexist. Sleep is encouraged by all those causes that reduce sensory excitations, namely darkness, silence, the recumbent position, and fatigue; conversely, it may be hindered by movements, intermittent noises, emotions, physical pain, worries, etc.

The following are included among sleep disorders: 1. Simple constitutional hypersomnia: this is characterized by a particular tendency to fall asleep even during the day when conditions are partly favourable, such as warmth, silence, or boredom. 2. True hypersomnia: this consists in a marked disposition to fall into a deep sleep even when environmental conditions are unsuitable. 3. Narcolepsy: a paroxysmal attack of sleep in which the patient experiences irresistible drowsiness: his eyelids close, he falls asleep, and this sleep lasts from a quarter of an hour to one or even two hours; he then awakens refreshed and ready to resume his occupations. There may be one or several attacks a day. The attacks begin suddenly and rapidly, but not violently, so that the patient often has time to choose a place to sleep. It may be associated with cataplexy: the patient falls to the ground for a few moments, but his fall is not as abrupt as in an apoplectic event or an epileptic seizure; he remains fully conscious during the attack but cannot utter a word. This attack lasts a few seconds or minutes, and sometimes even half an hour; the patient then gets up and immediately resumes the interrupted occupations. The association of narcolepsy with cataplexy constitutes Gélineau’s syndrome; both the former and the latter are related to emotional events. 4. Lethargic encephalitis: it is caused by a filterable virus believed to possess a marked nervous affinity, especially for the grey matter of the third ventricle. It manifests itself through more or less pronounced drowsiness and phenomena of deficit of the cranial nerves, especially those innervating the external musculature of the eye. 5. Sleep disease or African trypanosomiasis: it is caused by trypanosoma gambiense, transmitted by glossina palpalis, and by trypanosoma rhodense, transmitted by glossina morsitans, flies of the tsetse type. It is characterized by fever, enlargement of certain glands, drowsiness, followed by prolonged sleep and terminal coma. 6. Hypnotism (v.): this is sleep artificially induced through suggestion. 7. Insomnia: this consists in difficulty falling asleep or in difficulty resuming sleep after awakening. Insomnia of the first period is found in erethistic subjects, in persons who digest poorly, and in many children who have dreams that make an impression on them; it sometimes depends on the patient’s position, as in cardiac patients who awaken easily when lying on their backs. Insomnia of the second period is found in chronic alcohol intoxication, the abuse of coffee, poor digestion, sexual excesses, painful conditions, after exhausting work, and in anxious states.

Among the substances capable of inducing sleep, the opiates and barbiturates should be mentioned; they are administered orally or by injection. Ether, chloroform, nitrous oxide, and ethyl chloride are used by inhalation. Other substances, such as Simpanina, Pervitin, etc., serve to combat drowsiness.

II. VARIOUS THEORIES OF THE INTERPRETATION OF THE GENESIS OF S

Numerous theories seek to explain the genesis of s. In 1875 Blumenthal maintained that s. was due to cerebral ischemia, but Czerny in 1891 and Brodmann in 1902 demonstrated that in s. there is instead dilation of the cerebral vessels. W. Preyer in 1875 held that s. is produced by the accumulation in the organism of hypnogenic substances produced by fatigue. Two facts stand against this theory: first of all, there is no correspondence between the degree of fatigue and the depth of s.; secondly, s. produced by monotonous noises, darkness, and silence remains unexplained. In 1895 Lépine attributed s. to the retraction of the cerebral branches of the central sensory neuron, similar to that of pseudopodia; upon awakening, these branches would lengthen; however, Ramon y Cajal and others denied the existence of these amoeboid movements. In 1905 Claparède put forward the psychological theory of s.: primitive man defended himself through s. against the discomforts of the night, hence the need to sleep at night, hereditarily transmitted by his ancestors. S. would be a reaction of disinterest. In 1913 Piéron, after finding that the injection of cerebrospinal fluid from a dog in a state of insomnia into an awakened dog induces profound s. in the latter, held that this was caused by a very powerful hypnotic substance produced by the brain in the waking state. It has, however, been demonstrated that analogous effects are produced by injections of normal cerebrospinal fluid. Zondek and Bier advanced the hypothesis that the pituitary gland produces a brominated hormone with hypnotic action. In 1927 Pavlov put forward a theory according to which s. would be the effect of a process of irradiated internal inhibition. But the theory is at least incomplete, because it does not explain, for example, the s. of newborns, who sleep before they have acquired conditioned reflexes. In 1929 Kleitman explained s. by the reduction of the afferent stimuli that continuously reach the cortex, and more particularly by that of the proprioceptive excitations originating in the muscles under the influence of muscular tone. This decrease in excitations, caused by fatigue or muscular relaxation, would be the most important factor in the onset of s.

In all the theories cited above, primary consideration has been given to the cortical substrate of the brain. The fact remains, however, that observers who have carried out studies on animals, especially dogs and cats, have noted that following decortication, states of drowsiness appear in them just the same, at least apparently, no different from those observed in normal animals. The sole effect produced by decortication, Spadolini observes, is to convert the periodicity of s. and wakefulness from a diurnal monophasic type (long s. during the night and brief states of drowsiness during the day) to a polyphasic type characteristic of the suckling animal, which has several periods of drowsiness during its hours.

Recent studies, which began with the epidemic of lethargic encephalitis in 1917, have established that, without denying the importance of the cerebral cortex, the subcortical centers are of great significance in producing the phenomenon of s. Among the authors who have dealt with the question, Demole may be recalled, as in 1921 he observed in the cat that injection into the infundibular region of infinitesimal doses of a Ringer solution, with calcium chloride added, caused the animal to fall asleep. Hesa obtained the same results through mechanical and electrical stimulation. Similarly, Foerster and Gagel on the one hand, and C. Vincent on the other, during surgical procedures observed in man that mechanical stimuli applied to the floor of the third ventricle, in the perinfundibular region, produced irresistible drowsiness in the patient. The localization of this center was subsequently specified by Etors, Bayley, and Harrison, who placed it in the region of the posterior nuclei and the mammillary bodies. It is probable that there is one center for s. and another for awakening. According to A. Salmon, the posterior pituitary would also have considerable importance in the regulation of s.

Sleep is also taken into consideration by law, insofar as it deprives a person of the capacity to understand and to will; by depriving the subject of the legal order of knowledge and awareness of his own acts, it thus renders him incapable of expressing a legally effective will, of being held imputable for unlawful or criminal conduct. Natural sleep, as is readily understood, is the most normal and complete case of incapacity of the person, depriving him of all power of self-determination; generally, indeed, it is accompanied by an almost absolute inertia and immobility of the body (CIC, can. 2201 § 1; Cod. pen. ital., art. 42).

The case of artificial sleep is different, for which various forms are usually distinguished, among them hypnosis, narcosis, narcoanalysis (v.), and somnambulism. All of these concern the law according to the degree of deprivation of free determination of one’s acts that they produce in the subject. And since this involves a restriction of liberty to which the subject is subjected by third parties, the first three forms are unquestionably sanctioned by the Constitution of the Italian Republic itself, in art. 13. As for the hypnotized person—who acts like an automaton, commanded by others—the law considers him not imputable for the purposes of criminal law and incapable of acting for the purposes of civil law, if the hypnosis is genuine and complete. Punishable, however, will be the person who instigated the hypnotization, or the hypnotized person himself who submitted to such suggestion in order to commit an offense with impunity (Cod. pen., artt. 86, 87, 613; Cod. civ., artt. 591, 1425, 2046). Hypnotization for therapeutic purposes is nevertheless permitted (Cod. pen., art. 728).

As for narcosis, which is accompanied by absolute physical immobility, anyone who has taken advantage of this artificial sleep for illicit purposes against a person may be punished (Cod. pen., artt. 519 n. 3, 521-579 n. 2). Narcoanalysis, moreover, cannot be admitted in criminal law either as an investigative means or as an expert examination (Cod. proc. penale, artt. 314, 365), nor can it be considered a judicial experiment (Cod. proc. pen., art. 312): it should be remembered that narcoanalysis employs the so-called “truth serum” and other drugs.

The same things may be said of the sleep of the somnambulist, whose pathological condition enables him to perform various acts, but without any will, and therefore irrelevant in law: at most, responsibility may be attributed to whoever is obliged to supervise the somnambulist’s conduct.