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.