9. sleep

sleep

a behavior and an altered state of consciousness

how much of our lives do we spend sleeping?

1/3

3 things which electrophysiological instruments measure during sleep

• muscle tone (EMG)

• respiration, HR, blood pressure

• summated brain wave activity (EEG)

type of brain waves detected by EEG during wakefulness (synchrony, amplitude, frequency)

beta waves (13-30 Hz) (high arousal)

desynchrony, low amplitude, high frequency

type of brain waves detected by EEG when eyes are closed (synchrony, amplitude, frequency)

alpha waves (8-12 Hz)

synchrony, relatively high amplitude, low frequency

brain waves ordered from low to high arousal

delta < theta < alpha < beta

characteristics of low and high arousal waveforms

low - synchronous, high amplitude, low frequency

high - desynchronous, low amplitude, high frequency

6 sleep stages and what wave form activity characterizes each

• wakefulness - alpha and beta activity

• stage 1 - alpha and theta waves

• stage 2 - alpha and theta waves w sleep spindles (bursts of 12-14 Hz activity, aka beta waves) and K-complexes (bursts of delta waves of low frequency and high amplitude)

• stage 3 - 30% delta, 70% theta

• stage 4 - 50% delta, 50% theta

• REM - theta/alpha/beta activity

what are stages 3 and 4 (delta and theta activity) also called?

slow-wave sleep (SWS)

characteristics of non-REM sleep (stages 1-4)

• all EEG waveforms present

• light, even respiration

• muscle control present

characteristics of REM sleep

• presence of beta activity similar to wakefulness

• increased respiration and BP

• rapid eye mvmts (REM)

• loss of muscle tone (paralysis)

• VIVID, emotional dreams

• sexual arousal

length of basic sleep cycle

90 minutes

difference btwn dreams in stages 3-4 and REM

• dreams in stages 3-4 are “cold, rational” dreams that focus on reality

• dreams during REM are vivid, emotional, and irrational

infants sleep …% of the time. adults sleep …% of the time

80%, 30%

2 reasons why older ppl are prone to waking up over the course of the night

• UTIs increase w age

• reduced number of adenosine receptors in the vIPOA

in which 2 kinds of sleep do dreams occur?

SWS and REM sleep

REM sleep is accompanied by high lvls of blood flow in the …

visual association cortex (occipital)

when do nightmares occur?

stage 4 of SWS

2 potential functions of sleep

• may be an adaptive response

• restoration and repair

does exercise increase SWS or REM?

no

2 effects of sleep deprivation

• impaired ability to concentrate

• perceptual distortions/hallucinations

rats that are forced to walk on rotating platform lose sleep. what happens to these sleep deprived rats?

they eventually become ill and DIE

fatal familial insomnia is caused by what? what happens to humans w this?

genetic dmg to the hypothalamus

gradually become unable to sleep → eventually lose SWS → DIE

SWS may reflect…

restoration

REM sleep may reflect 2 things

• vigilance - alertness to the env (keeps brain alert and ready to awake)

• facilitation of brain dev - infants spend more time in REM sleep

SWS improves consolidation of … memories. REM improves consolidation of … memories

declarative/explicit

nondeclarative/implicit

declarative/explicit memories

things that you might need to process to recollect

e.g., test info

nondeclarative/implicit memories

things you don’t need to try to remember

e.g., throwing a ball

sleep rebound + % for stage 1 and 2, REM, and SWS

how much sleep you need to make up

stages 1 and 2 - 10%

REM - 50%

SWS - 70%

2 findings which show that it’s impossible for sleep to only be controlled by hormones

• siamese twins share same circulatory system, but sleep independently

• bottle-nose dolphins: the two hemispheres sleep independently

what does it mean if the “flipflop” is on? off?

on = alert/awake

off = asleep

ventrolateral pre-optic area (vlPOA)

if activated, it drives you toward sleep. if inhibited, you stay awake

basal brainstem and forebrain arousal systems

keeps organism awake thru various diffuse pathways. if these systems are inhibited, you fall asleep

what hormones do the basal brainstem and forebrain arousal systems involve?

ACh, NE, 5-HT, histamine

what are vlPOA and basal/forebrain areas both inhibited by?

2 GABA-ergic pathways

where are ACh neurons activated? what does this produce?

activated within ventral pons and basal forebrain

produces behavioral activation and beta waves

ACh agonists … arousal, ACh antagonists … arousal

increase, decrease

where are NE neurons located? when do they show high and low activity?

locus coeruleus in the dorsal pons

high activity during wakefulness

low activity during sleep (0 during REM sleep)

locus coeruleus neurons may play a role in…

vigilance

what does this graph show?

NE neuron firing rate

where is histamine located? what 4 parts of the brain does it project to? what does it produce?

located in tuberomamillary nucleus of the hypothalamus

project to the cerebral cortex, thalamus, basal forebrain, basal ganglia

cortical and behavioral arousal

5-HT/serotonin (where is it located/stimulated, what does it induce, what do its antagonists do, what 4 parts of the brain does it effect, when is it most released and not released?)

located in the raphe nuclei (medulla and pons)

induces cortical arousal

antagonists reduce cortical arousal

widespread effects to thalamus, hypothalamus, basal ganglia, hippocampus

most released during waking, no release during REM

what does this graph show?

mean firing rate of 5-HT

orexin is located where? what does it do?

neurons located in lateral hypothalamus

activate all arousal systems

what activates orexin? what decreases orexin?

hunger and the day-night cycle

satiety

what does the ventrolateral preoptic area (VLPA) induce? how?

SWS

by secreting GABA, which suppresses alertness and induces SWS

lesions of the vlPOA

produce total insomnia, leading to death

electrical stimulation of the vlPOA

induces signs of drowsiness in cats

what chemical initiates vlPOA activity?

ADENOSINE

what is adenosine produced by and when? what does accumulation of adenosine cause and thus allow?

produced by astrocytes when lacking glycogen — essentially when the brain is running out of energy

accumulation of adenosine causes drowsiness → allows for the restoration of glycogen

what are circadian rhythms moderated by? where is it? what is its role?

moderated by the suprachiasmatic nucleus (SCN) of the hypothalamus

just above optic chiasm

role in sleep, eating, behavioral activity

where does the SCN receive info from?

from retina

does the SCN receive info from rods or cones?

NO

what detects light and dark around ganglion cells? which pathway does this info run thru?

melanopsin

retinohypothalamic pathway

caffeine

an adenosine receptor agonist — decreases need for sleep

jet lag

disconnection btwn your SCN’s cycle and climate/time

2 functions of SCN

• inhibit the vIPOA, thereby increasing arousal (inhibiting sleep)

• excite orexinergic neurons and increase arousal

what brain part is important for the control of REM sleep? where does it sends projections to? what are the first indicators of REM sleep? what kinds of neurons and in where promote REM sleep?

the pons

sends projections to medulla, a pathway which inhibits muscle mvmt

PGO (pons-geniculate-occipital) waves

ACh neurons in the peribrachial pons (dorsal)

what 3 parts of the brain do pontine ACh neurons project to? what do they control? is it excitatory or inhibitory?

thalamus - control of cortical arousal

forebrain - arousal and desynchrony

tectum - rapid eye mvmts

excitatory

when the ventral pons system is activated by ACh, what is affected? what about the dorsal pons (peribrachial area)?

beta arousal and wakefulness

beta arousal and REM

insomnia

refers to a difficulty in getting to sleep or remaining asleep

3 causes of insomnia

• situational causes - some need more sleep than others

• drug-induced causes - use of sleeping pills can lead to insomnia

• sleep apnea

how to solve insomnia

try treating primary causes of it first (stress, etc.)

drug dependency insomnia is caused by

classic rebound effect from using sleeping pills

sleep apnea

person stops breathing and is awakened when blood lvls of carbon dioxide stimulate breathing

narcolepsy + (what chromosome is affected, rate it affects population)

sleeping at odd times

usually genetic on chromosome 6

~1 in 2000 ppl

3 types of narcolepsy

• sleep attack

• cataplexy

• sleep paralysis

sleep attack

urge to sleep during the day (boring times)

narcoleptics have reduced … lvls of the neuropeptide …

CSF, orexin

cataplexy + pathway

REM paralysis occurs, person is still conscious (excitement)

some problem from peribrachial pons → subcoeruleus nucleus → nucleus magnocellularis of the medulla → descending motor neurons

sleep paralysis + what it may sometimes involve

inability to move just prior to sleeping or just after waking

sometimes involve REM-like dreams