Dreams

notes from "Dreaming: A Very Short Introduction"

What is dreaming?

These are the cardinal cognitive features of dreaming:

• Loss of awareness of self (self-reflective awareness)
• Loss of directed thought
• Reduction in logical reasoning
• Poor memory both within and after the dream

And so:

• It never occurs to me that I am dreaming
• There is a flagrant disregard for the constancies of time, place, and person
• There is a processing of extreme associations - a hyperassociative processing

There is mental activity during sleep. Some mental function are enhanced, while others are diminished. In dreaming there is both:

• Selective activation of brain circuits underlying emotion and related percepts in REM sleep, and
• Selective inactivation of circuits and chemicals underlying memory, direct thought, self-reflective awareness, and logical reasoning

A typical REM sleep report includes:

• Rich and varied internal percepts, especially sensorimotor, audiory, and anti-gravitational hallucinations
• Delusional acceptance of the wild events as real despite their extreme improbability
• Bizarreness deriving from the discontinuity and character incongruity - settings are indefinite, characters are vaguely defined, changing
• Emotional intensity and variety (fear, elation, and exuberance)
• Poor reasoning

If dreaming is not interrupted by awakening, it is rare to have recall. Poor or no dream recall by many people is a function of the abolition of memory during these brain activated phases of sleep. As the chemical systems that are responsible for recent memory are completely turned off when the brain is activated during sleep, it is difficult to have recall unless an awakening occurs to restore the availability of these chemicals to the brain.

Phases:

• Sleep onset
• Non-REM sleep
• REM sleep - dreaming doesn't just happen here, it is just the most ideal condition for it. Every 90 minutes and occupying 1.5 to 2hrs per night
• Waking
• Awake - dreaming is essentially impossible

Associationism:

• asserts that memory is organized according to categorical similarities among objects, people, ideas, and so on, to every category of content.
• David Hartley thought that dreams were bizarre because there were too many associations. For him, dreaming served to loosen associations that were otherwise inclined to become obsessively fixed. 'And that would be madness'.
• Associations are not associations unless they have meaningful connections.

The brain is activated during sleep:

• The reflex brain is not completely dependent on external stimuli - it is capable of spontaneous activity
• Neuronal activation is continuous during sleep
• Dreaming has no particular function in and of itself. it is nothing but our occasional awareness of brain activation in sleep. It is this activation that:
  • establishes psychic equilibrium,
  • integrates recent and past learning,
  • casts our inventory of personal information in emotionally salient terms

Cells and molecules of the dreaming brain

The neurotransmitters that are directly responsible for neuronal excitability include glutamate (excitatory) and gamma-aminobutyric acid or GABA (inhibitory).

• REM sleep helps body temperature regulation, perhaps the most basic of all mammalian housekeeping functions
• REM sleep facilitates the consolidation and advancement of procedural learning, which is an acquired ability to do things when consciousness may not be involved
• REM sleep blocks the motor system at the level of the spinal cord, to make real movement impossible even if the upper brain elaborated and commanded the rich behaviors that we perceive in our dream scenarios.
• The visual brain stimulates itself in REM sleep via a mechanism reflected in EEG recordings as PGO waves. Originating in the pons from the neurons that move the eyes, these signals are conducted both to the lateral geniculate body in the thalamus and to the occipital cortex.

Brain state is set by the mode of information processing:

• when the brain switches from a "store and remember" to a "don't store and forget" mode
• when it switches from linear logical to a parallel associative mode
• All of these mode switches can go on in small but significant ways in waking, but they become obligatory, pronounced, and fixed when the brain enters REM sleep.
• The seratonin and noradrenaline cells that modulate the brain during waking reduce their output by half during non-REM sleep but are shut off completely during REM sleep. This means that the electrically reactivated brain is working without the participation of two of its chemical systems that mediate the waking state, and that are implicated in attention, memory and reflective thought, which are lost in dreaming.
• These changes are controlled by neuromodularity neurons that are few, small, and localized to a few brain stem nuclei, but which project their fine, multiply-branching processes all over the brain and spinal cord.
• These neurons are a sort of brain-within-the-brain which can automatically and forcibly change the microclimate of the rest of the brain, like a central thermostat. They are in the pons, project up to the thalamus and cortex and down to the spinal cord.
• We can trigger REM sleep by injecting very small amounts of a cholinergic drug into the pons. REM sleep dreaming is mediated by acetycholine when noradrenaline and serotonin are at very low levels.
• The brain functions well only if the cholinergic system is operating within certain limits.

Why Activate the Brain During Sleep?

Dreaming starts early:

• At 30 weeks in the womb, the fetus spends almost 24h a day in a brain-activated state like a first level of REM sleep
• At birth at least 8hrs of full REM sleep a day. To:
  • Build the brain stem, which controls the most primordial, first-line regulatory systems - temperature, cardiovascular, respiratory, and other
  • Then the cholinergic system, which mediates internal bodily activation, including the shifts from sleeping to waking.
  • Then the aminergic system, including histamine and dopamine
• Only mammals have thermoregulation and only mammals have REM sleep, and it is only in REM sleep that mammals cannot thermoregulate.

Dreaming helps us:

• Reorder the information inside our heads, to get rid of certain obsolete memories, to update memories, and to incorporate new experiences into our memory systems
• As REM sleep is far more prevalent in newborn infants than in adults, it seems likely that it constructs the brain itself
• Resting and restoring the aminergic systems at night lets us strengthen our capacity for thermoregulation and acquisition of information. These systems also support alertness, attention, and even analytical intellect
• Our dreams are emotional and hyperassociative because our brains are activated by cholinergic rather than aminergic chemicals. Emotional salience or relevance is a general mnemonic rule. Our level of emotional competence has a high survival value and underlies the more precise information needed to function socially, to allow us to know when to approach, when to mate, when to be afraid or to run for cover

Disorders of dreaming / dreaming and mental illness

• Dreams from which we spontaneously awaken are often dominated by anxiety, fear, and anger
• To fall asleep we have to assume postures that are immobile, ie to disable the motor system

• formally speaking, dreaming and severe mental illness are identical
• Mental state is a constantly negotiated compromise between the poles of waking sanity and dreaming madness
• Depression leads to more REM sleep. It could be that to be prone to depression is to be prone to REM sleep and vice versa
• The most effective antidepressant medications suppress REM sleep (by beefing up the depressed aminergic system and toning down the hyperactive cholinergic system), though sleep is affected before mood

Neuropsychology of dreaming

Studies show in REM sleep:

• an increase in activation of the cortical areas of the parietal lobe that are associated with hallucinatory perception
• a decrease in activation of the dorsolateral prefrontal cortex, associated with working memory, self-reflection, and directed thought
• Dreams are perceptually intense, instinctive, emotional, and hyperassociative because the brain regions supporting these functions are more active
• We can't decide properly what state we are in, can't keep track of time, place, or person, and can't think critically or actively because these brain regions are less active
• REM sleep has a lack of noradrenaline and serotonin, which are necessary for attention, learning, memory, orientation, and active reasoning
• It has an uninhibited cholinergic system associated with hallucinosis, hyperassociation, and hyperemotionality

• A complete loss of dreaming can occur when there is damage to the multimodal sensory cortex (in the parietal cortex) or to the deep frontal white matter of the brain.
• Epilepsy is a condition in which brain regions may be enhanced as well as impaired and is the opposite of stroke.