Sleep and Dreaming

The very function of sleep is unclear. Two hypotheses are that it is restorative, or that it serves an adaptive function (mostly related to safety and feeding needs)

Circadian Rhythms are rhythms about a day long

The suprachiasmatic nucleus (SCN) of the hypothalamus is the main (although not the only) “clock” controlling the circadian rhythm

Zeitgebers are environmental stimuli that help regulate the sleep/wake cycle

The SCN triggers a release of melatonin from the pineal gland, which induces sleepiness

Light information reaches the SCN through a direct connection from non-visual receptors in the retinas

Rhythms During Waking and Sleeping include many ultradian rhythms,

cycles that are shorter than a day. Among these is the stages of sleep. A

complete cycle through the various sleep stages takes approximately 90

minutes

The Functions of REM Sleep are viewed differently by different schools of psychology

Dreaming

To psychoanalysts dreams reveal the unconscious

The Activation Synthesis Hypothesis states that during REM sleep the forebrain integrates neural activity generated by the brainstem with information stored in memory

According to another hypothesis, REM sleep promotes neural development during childhood

Another hypothesis states that REM sleep is involved in learning

Some researchers believe REM sleep enhances consolidation

The “reverse learning” hypothesis states that the role of REM sleep is to clean up connections that make learning

more efficient

Comparison of animal and human studies indicates that REM sleep enhances non-declarative learning

The Functions of Slow Wave Sleep

Brain recuperation appears to be a more important function than body rest

There is evidence SWS contributes to consolidation of declarative memories

Brain Structures and Sleep

The basal forebrain contains both sleep-related cells and cells related to waking.

The sleep-related cells inhibit activating systems in the hypothalamus and brainstem

The sleep cells receive their input from the preoptic area and anterior hypothalamus (POAH).

POAH is particularly involved in slow wave sleep

The pons

The pons is the source of P00 waves during REM sleep. They apparently trigger the EEG desynchrony of REM

The pons sends impulses to the magnocellular nucleus to produce the atonia of REM. Disordered atonia is seen in cataplexy, a form of narcolepsy

Sleep as a Form of Consciousness

People can be both mentally and physically active while they dream

The gradations of sleep lead us to confront the question of what defines consciousness

The Neural Bases of Consciousness

The thalamus is probably responsible for awareness

The question of how the brain combines information about an object is referred to as the binding problem

Awareness is not necessary for all the important things the brain does

Attention refers to how the brain allocates its limited resources.

It is a physiological process, and changes in attention are matched with changes in neural activity

The pulvinar, a group of nuclei in the thalamus, appears to shift attention among stimuli

The Sense of Self

Some Origins of the Self

Body Image

Disrupions of t body image diminish the sense of self

Phantom limb studies suggest that this part of the self is a part of the neural structure

Memory

Without long term memory the existence of a self would probably be impossible

Confabulation suggests the importance of memory to the self identity

Disorders of Self

The Split Brain and the Self

Separation of the hemispheres gives us the opportunity to observe different aspects of consciousness

Gazzaniga believes that the left hemisphere contains a brain interpreter, which integrates the cognitive processes going on in other modules of the brain

Dissociative Identity Disorder (DID)

Also known as multiple personality disorder, this condition involves shifts in consciousness and behavior that seem to suggest distinct personalities

Bower attributes DID to state-dependent learning

Researchers have observed several physiological differences between personality states in DID patients