The Very, Very Strange Properties of REM Sleep
Most cognitive products of the Mind are produced by relatively straightforward activation/de-activation patterns in widely distributed neural networks of the brain. When for example, a highly complex cognitive product like a sentence or a story is produced by your mind, it generally is associated with those particular brain activation/de-activation patterns as well as mild emotional changes in your psyche and mild arousal levels in your body. Not so with dreams.
Dreams are highly complex cognitive products that are produced, as far as we can tell, by Rapid eye movement (REM) sleep. While REM sleep is also composed of a series of particular brain activation/de-activation patterns, bodily and emotional arousal patterns are anything but mild.
Relative to the waking state, sympathetic nervous system activity rises dramatically during phasic portions of REM. As the average duration of REM episodes increase over the course of the night, so do the durations of sympathetic discharges giving rise to periodic REM-related sympathetic discharges or “storms.”
These autonomic nervous system (ANS) storms, in turn, may be linked to a host of negative cardiopulmonary changes that occur during REM. During all REM periods, an acceleration of heart rate occurs at least 10 beats before EEG signs of phasic arousal, and then fluctuates dramatically during phasic REM. Systemic arterial blood pressure (BP), pulmonary BP, and intracranial arterial BP all exhibit increased variability relative to NREM and waking levels. Because of the hemodynamic, ANS, and sympathetic alterations of REM, plaque rupture and coronary arterial spasm become more likely. Persons with cardiopulmonary disease are indeed more likely to die during this REM period than at any other time of the 24-hour day.
In addition, during REM oxygen desaturation levels are maximal and Cheyne-Stokes-like breathing patterns predominate. As a result of the fall in alveolar ventilation, there are changes in blood gas levels, with rises in CO2 and decreases in oxygen saturation. The natural response to lowered O2 levels is to increase inspiratory breathing, but this response (the hypoxic ventilatory response) is decreased by over 50% of normal capacity during REM. The REM-related hypoxemia and abnormal breathing patterns may cause life-threatening complications in vulnerable persons, including infants with immature lung capacity thus increasing the chance for sudden infant death syndrome.
REM also appears to involve a loss of thermo-regulatory reflexes so that it is harder for the individual to stop heat loss during REM sleep. Although brain temperature rises during REM, thermoregulatory responses such as sweating and panting do not occur in REM.
Yet another bizarre feature of REM is that phasic eye movements and muscle twitches occur upon a background of paralysis in the antigravity musculature, including the jaw, neck, and limbs. This paralysis however does not extend to the sexual organs! In males every REM period is associated with prolonged penile erections. These REM-related erections apparently even occur in infants. They persist throughout the lifespan but are not reliably associated with erotic desire. Women sometimes undergo uterine contractions and pelvic thrusting during REM, but too few studies have been done on this topic to draw any firm conclusions.
In short whenever we go into REM sleep we experience intense ANS storms, cardiovascular instabilities, respiratory impairment, thermoregulatory lapses, muscle twitching, muscle paralysis and penile erections. Now recall that the cognitive products associated with this strange set of physiologic aberrations are what we call dreams. Is it any wonder that theorists of REM sleep have despaired of ever identifying the evolutionary or physiologic functions of REM sleep?
One note I would make is that the Gestalt Bubble reality neuro-simulator hardware we call a brain appears to run on photons, so the main function of REM itself might just be bringing light in to jump-start the holographic game engine.