SLEEP. — From a biological standpoint, sleep reveals itself as an aspect of a phenomenon common to all living beings, in the animal and plant kingdoms, which alternate between 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 especially of muscle tone, without any significant lowering of basal metabolism or noticeable slowing of vegetative functions.
I. PHYSIO-PATHOLOGY OF SLEEP
The transition from the waking state to that of sleep is normally progressive and is heralded by a sense of fatigue, heaviness, lassitude, disinterest in what is happening around us, and difficulty in keeping the eyes open; it follows an alternation of phases of attention and inattention during which hypnagogic hallucinations occur, represented by disconnected, fleeting images that undergo rapid metamorphoses and vanish when the eyes are opened or moved.In sleep, there is a predominance of relaxation in all the musculature, except for the masseters, the orbicularis oculi, the sphincters, and the fists in children. The pupils are constricted and the eyeballs are rotated upward and outward. The number of heartbeats decreases by 10–30 per minute, and blood pressure by 10–20 mm Hg. The number of respiratory excursions also decreases, with a long, noisy inspiratory phase and a rapid expiratory phase. Basal metabolism drops by 10–15% in deep sleep, and body temperature falls by a few tenths of a degree. Sweat secretion increases in deep sleep, and urine is less abundant but denser, more acidic, and richer in phosphates. Gastric function does not undergo significant changes. Cerebral activity is diminished but not abolished. In the electroencephalogram, all rapid waves disappear in deep sleep, and only very slow waves persist. The average duration of physiological sleep varies according to age, constitution, occupation, and season; in general, newborns sleep 20 hours a day, children from one to seven years old sleep 10 to 14 hours, adults sleep 7 to 9 hours, and the elderly sleep 5 to 6 hours. Sleep is an indispensable need of the organism. Some researchers, including Kleitman, have observed that after 80–115 hours of sleeplessness, the individuals they studied exhibited mild psychological disturbances; however, it has been found that prolonged insomnia of ten days can lead to death in humans if other sufferings coexist. Sleep is facilitated by all those causes that reduce sensory excitations, such as darkness, silence, the supine position, and fatigue; conversely, it can be hindered by movement, discontinuous noises, emotions, physical pain, worries, etc.
Among the disorders of sleep, the following may be noted:
1. Simple constitutional hypersomnia: characterized by a particular tendency to fall asleep even during the day under partially favorable conditions such as warmth, silence, or boredom.
2. True hypersomnia: consists of a marked tendency to fall into deep sleep even when environmental conditions are not conducive.
3. Narcolepsy: a paroxysmal sleep crisis in which the patient feels an 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 wakes up refreshed and ready to resume his activities. One or several attacks may occur in a day. The attacks begin suddenly and rapidly, but not brutally, so that the patient often has time to choose where 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 or epileptic attack; he remains fully conscious but unable to speak. This crisis lasts a few seconds or minutes, or even half an hour; then the patient gets up and immediately resumes his interrupted activities. The association of narcolepsy with cataplexy constitutes Gelineau’s syndrome; both are related to emotional factors.
4. Lethargic encephalitis: caused by a filterable virus believed to have a marked affinity for the nervous system, especially the gray matter of the third ventricle. It manifests with more or less pronounced drowsiness and deficits in the cranial nerves, especially those innervating the external ocular muscles.
5. Sleeping sickness or African trypanosomiasis: caused by *Trypanosoma gambiense*, transmitted by *Glossina palpalis*, and *Trypanosoma rhodesiense*, transmitted by *Glossina morsitans*, tsetse flies. It is characterized by fever, enlargement of certain glands, drowsiness, and then prolonged sleep leading to terminal coma.
6. Hypnosis (v.): sleep artificially induced by means of suggestion.
7. Insomnia: consists of difficulty in falling asleep or in resuming sleep after waking. Insomnia of the first period is found in excitable subjects, in people with poor digestion, and in many children who are disturbed by dreams; sometimes it depends on the patient’s position, as in cardiac patients who wake easily when lying on their backs. Insomnia of the second period is found in chronic alcohol intoxication, excessive coffee consumption, active digestion, and sexual excesses. It also occurs in painful conditions, after fatiguing work, and in anxious states.
Among the substances capable of inducing sleep, opiates and barbiturates, administered orally or by injection, should be mentioned, as well as ether, chloroform, nitrous oxide, and ethyl chloride, used by inhalation. Other substances such as simpanine, pervitin, etc., are used to combat drowsiness.
II. VARIOUS THEORIES ON THE INTERPRETATION OF THE ORIGIN OF SLEEP
Numerous theories attempt to explain the origin of sleep. In 1875, Blumenthal suggested that sleep is due to cerebral ischemia, but Czerny in 1891 and Brodmann in 1902 demonstrated that in sleep there is instead a dilation of the cerebral vessels. W. Preyer in 1875 argued that sleep is produced by the accumulation in the organism of hypogenic substances generated by fatigue. Two facts contradict this theory: first, there is no correspondence between the degree of fatigue and the depth of sleep; second, it fails to explain sleep induced by monotonous noises, darkness, or silence. In 1895, Épin claimed that sleep results from the retraction of the cerebral ramifications of the central sensory neuron, similar to the movement of pseudopodia; upon waking, these ramifications would lengthen. However, Ramón y Cajal and others denied the existence of such amoeboid movements. In 1905, Claparède proposed the psychological theory of sleep: primitive man defended himself from the discomforts of night by sleeping, and this need to sleep at night was inherited from ancestors. Sleep would thus be a reaction of disengagement.
In 1913, after observing that the injection of cerebrospinal fluid from a dog in a state of insomnia into an awake dog induced deep sleep in the latter, Piéron concluded that sleep is caused by a hypnotoxin produced by the brain during wakefulness. However, it has been shown that similar effects can be produced by injections of normal cerebrospinal fluid. Zondek and Bier hypothesized that the pituitary gland produces a brominated hormone with hypnotic action. Pavlov in 1927 advanced a theory according to which sleep would be the effect of an internal inhibition process spreading through the brain. Yet this theory is at least incomplete, as it does not explain, for example, sleep in newborns, who sleep before acquiring conditioned reflexes. In 1929, Kleitman explained sleep as a reduction of afferent stimuli continuously reaching the cortex, particularly proprioceptive stimuli originating from muscles under the influence of muscle tone. This decrease in stimulation, due to fatigue or muscular relaxation, would be the most important factor in the onset of sleep.
In all the above theories, the cortical substrate of the brain has been given primary consideration. Yet observers who have studied animals, especially dogs and cats, have noted that after decortication, these animals still exhibit states of drowsiness indistinguishable from those observed in normal animals. The only effect of decortication, as Spadolini observes, is to convert the periodicity of sleep and wakefulness from a monophasic pattern (long sleep at night and brief drowsiness during the day) to a polyphasic pattern characteristic of suckling animals, which display several periods of drowsiness within 24 hours.
Recent studies, which began with the epidemic of encephalitis lethargica in 1917, have established that, without disregarding the importance of the cerebral cortex, subcortical centers play a major role in the production of sleep. Among the authors who have addressed this issue is Demole, who in 1921 observed in cats that the injection of infinitesimal doses of Ringer’s solution with calcium chloride into the infundibular region induced sleep in the animal. Hess achieved the same results through mechanical and electrical stimulation. Similarly, Foerster and Gagel on one hand and C. Vincent on the other, during surgical procedures in humans, observed that mechanical stimulation in the floor of the third ventricle, in the perinfundibular region, provoked irresistible drowsiness in the patient. The localization of this center was later refined by Etors, Bailey, and Harrison, who placed it in the region of the posterior nuclei and the mammillary bodies. It is likely that there exists a sleep center and a wakefulness center. According to A. Salmon, the posterior pituitary also plays a significant role in the regulation of sleep.
II. ETHICAL AND LEGAL NOTES
During sleep, there is no responsibility *per se*, since the basis for any imputability—the use of reason—is lacking. Responsibility may arise only in cases where the causes of certain phenomena occurring during sleep were consciously set beforehand, for example, in erotic dreams (v. dream) and seminal emissions during sleep, or in cases of artificially induced sleep (v. HYPNOTISM). Regarding seminal emissions during sleep, preceded by erotic dreams, it should be noted that these are purely physiological and natural phenomena and therefore not imputable. The state of *dormitio*, which precedes or follows deep sleep, is a state in which full use of reason is not present, and thus imputability and responsibility are diminished.
Sleep is also considered by law insofar as it deprives the person of the capacity to understand and to will; by removing from the subject of the legal order the knowledge and awareness of their own actions, it renders the person incapable of forming a legally effective will, of being held accountable for illicit or criminal behavior. Natural sleep, of course, is the most normal and complete case of a person’s incapacity, depriving them of all autonomous power; it is generally accompanied by an almost absolute inertia and immobility of the body (CIC, can. 2201 § 1; Italian Penal Code, art. 42).
Different is the case of artificial sleep, for which various forms can be distinguished, including hypnosis, narcosis, narcoanalysis (v.), and somnambulism. All of these are of legal interest depending on the degree of lack of free determination of one’s actions that they produce in the subject. Since these involve a restriction of freedom imposed by third parties, the first three forms are directly sanctioned by the Italian Constitution itself, in Article 13. As for the situation in which a person is made to act like an automaton, controlled by others—the law considers them not imputable under criminal law and incapable of acting under civil law, if the conditioning is genuine and complete. However, the person who induced the conditioning or the subject who submitted to such suggestion in order to commit a crime without punishment will be punishable (Penal Code, arts. 86, 87, 613; Civil Code, arts. 591, 1425, 2046). Conditioning for necessary medical treatment is, however, permitted (Penal Code, art. 728).
As for narcosis, which is accompanied by physiological immobility, the person who takes advantage of this artificial sleep for illicit purposes against another person may be punished (Penal Code, arts. 519 n. 3, 521–579 n. 2). Narcoanalysis, moreover, cannot be admitted in criminal law either as an investigative tool or as a means of expert examination (Code of Criminal Procedure, arts. 314, 365), nor can it be considered a judicial experiment (Code of Criminal Procedure, art. 312); it should be noted that narcoanalysis employs the so-called “truth serum” and other drugs.
The same things can be said of the state of the sleepwalker, in which a morbid condition allows him to perform various acts, but without any will, and therefore irrelevant to the law: there may be a case for responsibility only in the person who is bound to supervise the sleepwalker’s conduct.