Brain and Cognition Module 3 Chapter 8 Sleep, Dreaming, and Circadian Rhythms

electroencephalogram (EEG)

An amplified recording of the waves of electrical activity that sweep across the brain's surface. These waves are measured by electrodes placed on the scalp.

electrooculogram (EOG)

Recording of eye movements.

electromyogram (EMG)

Record of the (intrinsic) electrical activity in a (skeletal) muscle.

alpha waves

- The relatively slow brain waves of a relaxed, awake state; - Waxing and waning bursts of 8- to 10-Hz EEG waves.

delta waves

- The large, slow brain waves associated with deep sleep; - The largest and slowest EEG waves, with a frequency of 1 to 2 Hz.

initial stage 1 EEG

- The period of the stage 1 EEG that occurs at the onset of sleep; it is not associated with REM; - Not marked by any striking electromyographic or electrooculographic changes.

emergent stage 1 EEG

Subsequent (following) periods of stage 1 sleep EEG, accompanied by REMs and by a loss of tone in the muscles of the body core

REM sleep

The sleep associated with emergent stage 1 EEG.

- NREM sleep (non-REM sleep) -

All other sleep stages 1-3 without rapid eye movements.

slow-wave sleep (SWS)

NREM 3 is often referred to as ... After the delta waves that characterize it; this in particular, rather than sleep in general, appears to play the major restorative role.

activation-synthesis hypothesis

The hypothesis that information supplied to the cortex by many brain-stem circuits during REM sleep is largely random and the resulting dream is the cortex's effort to make sense of these random signals.

recuperation theories of sleep

Theories based on the premise that being awake disturbs the body's homeostasis (internal physiological stability) and the function of sleep is to restore it.

adaption theories of sleep

Theories based on the premise that sleep is not a reaction to the disruptive effects of being awake but the result of an internal 24-hour timing mechanism.

executive function

Cognitive abilities that appear to depend on the prefrontal cortex; proved to be more susceptible to disruption by sleep loss; includes innovative thinking, lateral thinking, insightful thinking, and assimilating new information to update plans and strategies.

microsleeps

Brief periods of sleep, typically about 2 or 3 seconds long, during which the eyelids droop and the volunteers become less responsive to external stimuli, even though they remain sitting or standing.

carousal apparatus

An apparatus used to study the effects of sleep deprivation in laboratory rats; Critique: It may be that repeatedly being awakened by this apparatus kills the experimental rats not because it keeps them from sleeping but because it is stressful.

- the default theory of REM sleep -

The theory that suggests that it is difficult to stay in NREM sleep for long periods of times so the brain switches to one of two other states: If there are any immediate bodily needs to be taken care of, the brain switches to wakefulness; if there are no immediate needs, it switches to REM sleep.

circadian rhythms (circadian means ''lasting about a day'')

The 24-hour biological cycles found in humans and many other species.

zeitgebers (german for ''time givers'')

Environmental cues, such as the light-dark cycle, that entrain (control the timing of) circadian rhythms.

free-running rhythms

Circadian rhythm's in constant environments; their duration is called the free running period.

free-running period

The natural period of the rhythm if there are no external cues.

internal desynchronization

A state in which biological rhythms are not in phase (synchronized) with one another.

jet lag

Occurs when the zeitgebers that control the phases of various ciradian rhythms are accelerated during east-bound flights (phase advances) or decelerated during west-bound flights (phase delays).

- shift work -

Occurs when the zeitgebers stay the same, but workers are forced to adjust their natural sleep-wake cycles in order to meet the demands of changing work schedules.

circadian clock

An internal mechanism that maintains a 24-hour activity rhythm or cycle.

suprachiasmatic nuclei (SCN)

Nuclei of the medial hypothalamus that control the circadian cycles of various body functions.

melanopsin

A photopigment present in ganglion cells in the retina whose axons transmit information to the SCN and the the thalamus.

tau

The first mammilian circadian (mutated) gene to be identified.

- clock -

The first mammalian circadian gene to have its structure characterized.

The anterior hypothalamus and adjacent basal forebrain are thought to promote ...

sleep

The posterior hypothalamus and adjecent midbrain are thought to promote ...

wakefulness

cerveau isolé preparation (literally means ''isolated forebrain'')

Bremmer severed the brainstem of cats between their inferior colliculli and superior colliculi in order to disconnect their forebrains from ascending sensory input.

desynchronized EEG

A low amplitude, high-frequency EEG.

encéphale isolé preparation

An experimental preparation in which the brain is separated from the rest of the nervous system by a transection of the caudal brain stem; it did not disrupt the normal cycle of sleep EEG and wakefulness EEG.

reticular activating system (Moruzzi and Magoun)

Referring to the reticular formation because of the proposition that low levels of activity in the reticular formation produce sleep and that high levels produce wakefulness.

hypnotic drugs

Drugs that increase sleep.

antihypnotic drugs

Drugs that reduce sleep.

melatonin

Main drug that influences circadian rhythmicity.

benzodiazepines

Drugs developed and tested for the treatment of anxiety, but most commonly prescribed as hypnotic medications; in the short term, they increase drowsiness, decrease the time it takes to fall asleep, reduce the number of awakenings during a night's sleep, and increase total sleep time. Thus thay can be effective in the treatment of occasional difficulties in sleeping.

imidazopyridines

A class of GABAA agonists that were marketed for the treatment of insomnia.

5-hydroxytryptophan (5-HTP)

The precursor of serotonin that can readily pass through the blood-brain barrier; they do reverse insomnia produced in both cats and rats, but appear to have no terapeutic benefit in the treatment of human insomnia.

pineal gland

Brain structure located on the midline of the brain just ventral to the rear portion of the corpus callosum; The function in birds, reptiles, amphibians, and fish is the inherent timing properties and regulation of circadian rhythms and seasonal changes in reproductive behaviour through its release of melatonin; It plays a role in the development of mammilian sexual maturity, but its functions after puberty are not at all obvious.

chronobiotic

A substance that influences the timing of internal biological rhythms.

insomnia

Sleep disorder that includes all disorders of initiating and maintaining sleep.

hypersonmia

Sleep disorder that includes disorders of excessive sleep or sleepiness.

iatrogenic

Produced by a physician (the unexpected results from a treatment prescribed by a physician); In large part because sleeping pills (e.g., benzodiazepines), which are usually prescribed by physicians, are major because of insomnia.

sleep apnea

A disorder in which the person stops breathing for brief periods while asleep; It usually leads to a sense of having slept poorly and is thus often diagnosed as insomnia.

periodic limb movement disorder

A disorder characterized by periodic, involuntary movements of the limbs, often involving twitches of the legs during sleep.

restless legs syndrome

A neurological disorder characterized by uncomfortable feelings in the legs, producing a strong urge to move them; It keeps them from falling asleep.

narcolepsy

The most widely studied disorder of hypersomnia; Persons with this disorder experience severe daytime sleepiness and repeated, brief daytime sleep episodes, even during conversations, eating, while scuba diving, or while making love; Cataplexy, sleep paralysis, and hypnagogic hallucinations are other symptoms.

cataplexy

Symptom of narcolepsy; Characterized by recurring losses of muscle tone during wakefulness, often triggered by an emotional experience.

sleep paralysis

The inability to move just as one is falling asleep or waking up.

hypnagogic hallucinations

Dreamlike experiences during wakefulness.

orexin

A neuropeptide associated with narcolepsy; Several studies have documented reduced levels of orexin in the cerebrospinal fluid of individuals living with naroclepsy and in the brains of deceased individuals who had narcolepsy; The number of orexin-releasing neurons has been found to be reduced in the brains of persons with narcolepsy.

REM-sleep behaviour disorder

A neurological disorder in which the person does not become paralyzed during REM sleep and thus acts out dreams; Common in individuals with Parkinson's disease.

nucleus magnocellularis

Structure of the caudal reticular formation that evolved to control muscle relaxation during REM sleep; REM sleep without atonia is caused by damage to this structure or to an interruption of its output.

polyphasic sleep cycles

Sleep cycles that regularly involve more than one period of sleep per day; Displayed in most mammals and human infants.

monophasic sleep cycles

Sleep cycles that regularly involve only one period of sleep per day, typically at night; Displayed in most adult humans.

sleep inertia

Significant grogginess and impaired alertness after sleeping or napping.