Shakespeare knew nothing of REM (rapid eye movement) associated with dreaming but was certainly interested in sleep and dreams. There is much in his work that concerns sleep disorders and acts of automatism during sleep, the most striking example being the sleep-walking of Lady Macbeth. Other 'parasomnias' are sleep-talking, bed-rocking and night terrors, and these conditions have in common a link to deep sleep and rapid transition to wakefulness, and a tendency to fade out after adolescence.
At one time the parasomnias were thought to coincide with the third or fourth stages of REM sleep, but Broughton, after studying the activation of motor events, judged that they occured not in 'dreaming sleep' but in the confused state of arousal. This seems to be the prevaling view at present. In Macbeth, Shakespeare used the words 'sleep' or 'sleeping' more times than in any other of his plays - twenty-eight, in fact, and many more times than 'dreams' and 'dreaming'.
What had Shakespeare noted, long before studies of sleep and brain function? First, night-walking does occur in adults, although much less than in children (perhaps in about 15% of children, and 0,7% of adults). The Doctor of Physic in Macbeth has been watching for several nights before he observes Lady Macbeth's sleep-walking, although the waiting gentlewoman has seen it more frequently (and also noted her sleep-talking). Further, when the Doctor emphasizes 'You see her eyes are open' she replies 'Ay, but their sense is shut'. This inability to see has been reported in animals: arousal from slow-wave sleep produces long periods of inhibition of the primary visual cortex, confirming Broughton's hypothesis of 'changes in later visual-evoked potential components suggesting inhibitions or occlusions of visual pathways'.
Many of the motor acts that sleep-walkers perform are based on recently performed activities. According to the gentlewoman, 'Since his Majesty went into the field, I have seen her rise from bed, throw her nightgown upon her, unlock the closet, take forth paper, fold it, write upon it, read it, afterwards seal it, and again return to ber, yet all the while in a most fast sleep'. We are reminded what Lady Macbeth and her husband corresponded with each other when he was away from home in battle. Indeed, in her very first appearance in the play, she is shown reading the letter from Macbeth that contains the prophesy of the Weird Sisters.
Moving and vivid are the hand-washing gestures of Lady Macbeth during her sleep-walking, in her last appearance of the play, with the words 'Yet who whould have thought the old man had so much blood in him' - a reliving of her observation of the King's bloody corpse when she returned to Duncan's chamber to leave the daggers Macbeth had used for the murder and to 'smear the sleepy grooms with blood'. She then incorporates the knocking at the gate, which occured at the same time. Ordinarily in sleep-walking dreams, events of the day come into the following night's deep sleep, but Lady Macbeth incorporates events that occured weeks, if not months, before. Those who have been interested in the sleep-walking of Lady Macbeth and its underlying mental activity have always focused on the hand-wringing automatism. Freud had difficulty in classifying this behaviour, stating at a meeting of the Psychoanalysis Society in Vienna, after J. Sanger's case presentation, 'The case of Lady Macbeth is not one of ordinary somnolence, but something more like a nocturnal delirium', elsewhere classing Lady Macbeth's behaviour as mysophobia.
The 'Good Doctor', who confesses that Lady Macbeth's illness is beyond his practice is well aware that sleep walking seldom leads to accidental death ('I have known those which walked in their sleep who have died holily in their beds') - but as a careful clinician he sees that Lady Macbeth is deeple depressed and fears for her suicide: 'look after her, / Remove from her the means of all anoyances / And still keep eyes upon her'. This anxiety is borne out as the play out as the play ends, when Malcolm refers to this 'fiend-like queen / Who (as is thought) by self and violent hands / Took off her life'.
Shakespeare's interest in dreaming and sleeping should be looked at from the point of view of the early modern times (as the Renaissance is now labelled). Wittern, ih his fascinating summary of sleep theories of antiquity and the Renaissance, suggests that the basic concept was derived from Aristotle, along with some presocratic thinkers, and codified by Galen in the second century AD. According to this theory, when food is being digested and transformed inot blood, vapours develop which become warm and rise to the head. Gathered there, they condense in the cold brain and flow downward, driving warmth in front of them. Because of the rising vapours the head becomes thick and the eyes close; sleep occurs when the condensed vapours flow downward again and push warmth into the lower part of the body. A similar physiological process was believed to result from use of sleping potions or wine, or from physical exhaustion. Scholars still cannot decide whether Aristotle regarded the cooling of the brain as the deciding factor producing sleep or whether he believed sleep to be caused by the concentration of warmth in the heart.
For Galen, the direct cause of sleep was the lack of animal spirits in the somatic and kinetic organs. During the digestion of food or physical exhaustion a kind of misty diathesis rises from the inner part of the body to the brain, and entails the quiteude of most of the body. The noteworthy point here is that Shakespeare does not rely on this kind of explanation of sleep, but rather on metaphor:
'Sleep that knits up the raveled sleave of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great nature's second cause,
Chief nourisher in life's feast'
The keen Doctor rejects Macbeth's request that he find some herb or medicine to purge his wife's disorders to a 'sound and pristine health', raising the question of using 'rhubarb cymed [senna], or what purgative drug' in keeping with Galen's hypothesis, a trace of which I find in Macbeth's discovery of the image of the dagger he sees before him as 'a dagger of the mind, a false creation / Proceeding from the heat oppressed brain' (my emphasis) which is usually glossed as 'feverish.' In Macbeth, parasomnias run parallel with the fortunes of the two leading characters. As Lady Macbeth declines into guilt-ridden sickness, she acts out her distress in automatic letter-writing, hand-wringing, sleep-walking and sleep-talking. Her husband, just after the murder of King Duncan and his grooms, hears a voice cry out, 'Glamis hath murdered sleep and therefore Cawdor / Shall sleep no more! - Macbeth shall sleep no more!' Macbeth comes to envy Duncan, for in his grave the King sleep well while he himself is afraid to go to bed without the expectation of 'terrible dreams'. Even Lady Macbeth, after the appearance of the ghost of Banquo to Macbeth, cannot help pointing out to her husband, 'You lack the season of all natures, sleep'.
Psychologists, physiologists and sleep researchers cannot tell us which psychic forces lead to the differing disorders of sleep. Nor did Shakespeare in Macbeth, but he did not need to; he needed only to show the dramatic rightness of their differences.
