Neuro Ch 10 Sleep

• electroencephalography (EEG)
• records the summed activity of thousands of neurons, aka field potential 

can also use recording of eye movement via electrooculography or skeletal movement via electromyography

• (cycles per second)
• delta <4
• theta 4-8
• alpha 8-12
• beta 12-30
• gamma 20-100+

• REM = rapid eye movement sleep
• NREM = non rapid eye movement sleep (stages 1-3)

• heart rate and breathing are fast, small muscles can twitch
• major muscle groups are paralysed 
• brain's activity oscillates at a high frequency, similar to moments of concentration and complex cognitive function
• typically dreams

• 80% of sleep (stages 1-3)
• heart rate and breathing are slow
• in slow wave sleep (stage 3), brain's activity oscillates at a low frequency with high amplitude

• inability to move, speak, or react
• often accompanied by terrifying hallucinations

• promotes sleep when active
• damage here produces insomnia
• VLPO neurons release inhibitory NT to several areas of the brain, especially to the arousal network in the brainstem and forebrain

• regions that promote wakefulness and alertness
• locus coeruleus (nonrepinephrine) raphe nucleus (serotonin), tuberomammillary nucleus (histamine), cholinergic regions in pons and basal forebrain

• both engage in mutual inhibition
• when one is active, it uses inhibitory NT to suppress the other
• a bistable system, in which either sleep or wakefulness occur, but not both simultaneously

• brain looks like it does during wakefulness: presence of gamma oscillations
• before REM, cholinergic neurons in the pons become active: triggers atonia (paralysis) and results in pontogeniculo-occipital waves (originates in pons, move to LGN, then to occipital cortex)
• the cholinergic neurons that trigger REM are also involved in the arousal network

natural internal rhythm that runs on a 24 hour cycle and controls our sleep-wake cycles and other biological processes

• results from programmed mechanisms in our brains, and persists even in the absence of external cues
• primary pacemaker in mammals is the suprachiasmatic nucleus (SCN)

• cells in the SCN maintain their own rhythm (of gene expression) when cultured in a dish
• damage to the SCN obliterates a regular sleep-wake cycle

• entrainment: sync of ineternal rhythm to external rhythm
• zeitgebers: external environment cues help align circadian rhythm w/ light 
• circadian rhythm entrained by light-dark cycles (light goes from light-sensitive retinal ganglion cells containing melanopsin directly to the suprachiasmatic nucleus)

SCN sends signal to the pineal gland which produces and releases melatonin

• mismatch of circadian rhythm with the local day/light period
• long term disturbances can lead to stress hormone levels and reduced volume of the temporal lobes with accompanying deficits in spatial learning and memory

decrease in arousal because of endogenous melatonin interacting with its receptors in the SCN causes dip in energy

• monophasic (most common but no universal)
• biphasic
• everyman
• dymaxion
• uberman

• theories:
• for restoration,
• survival advantage,
• simulate rare situations,
• to process info

• saves energy and helps body recover 
• we have more SWS at night when we exercise more during the day
• serotonergic and noradrenergic neurons shut down during REM 
• caveats: REM-associated with high neural activity, some high active animals sleep little and low active sleep a lot

• sleep keeps us out of trouble dark hours
• advantageous for organisms who can't see well in the dark to avoid getting eaten or injured

caveats: darkness is a survival threat, why not develop night vision? what about dolphins?

• sleep (especially REM) provides us with a way of practising actions before we enact them in the real world 
• may be especially useful for maintaining circuits vital for survival, particularly if we may need to use them in a threatening environment 

caveats: no direct evidence, high crime areas don't have more threat dreams than low threat

• sleep plays important role in learning and memory 
• helps us consolidate important memories and forget less important ones

• linked to stabilisation or imporvment of motor procedural memories
• sleep has also been linked to stabilisation of declarative memories

many studies employ study test design with a 12 hr delay that either includes sleep or just wakefulness

• memory involves initial encoding then consolidation, which allows memories to be stabilised and maintained in the long term 
• consolidation seems to require sleep
• memories may be reactivated or replayed, enabling patterns to be strengthened and maintained

• helps to understand what we learn by restructuring info that we've learned to enable insight into underlying rules or commonalities 
• can help gain insight to problems
• help the discovery of hidden rules

• mild sleep deprivation associated with irritability, muscle aches, difficulty maintaining attention
• 1-1.5 hours of sleep = 32% decrease in alertness 
• more severe sleep deprivation is associated with microsleeps

• brief sleep periods in the seconds or subsecond range
• those who experience them are often unaware that they had a microsleep

• cognitive impairment
• memory lapses
• hallucinations
• ADHD like symptoms 
• impaired moral judgment
• decreased reaction time
• tremors
• muscles
• type 2 diabetes risk 
• compromised immune system
• increased risk of heart disease

long shifts mean sleep deprivation, which means poor decision making, more errors, less vigilance, and more accidents of death

difficulty falling asleep or maintaining sleep

• genetic disorder in which individuals lose the ability to sleep and progressively develop anxiety, hallucinations, and dementia; usually fatal within 1-3 years
• the envephalopathies are caused by abnormal proteins called prions

• excessive chronic sleepiness 
• interferes with normal functioning at work and with family individuals might map at inappropriate times 
• can occur as a result of medication for depression, as a result of excess body weight, or from brain damage

• characterised by hypersomnia and cataplexy (transient and sudden muscle weakening, often leading to collapse)
• often fall into REM from waking state

actions performed during sleep that are not under voluntary control

• when brain tries to move directly from SWS to wake but gets caught in between 
• somnambulism: sleepwalking

• REM sleep behaviour disorder: muscle atonia that usually accompanies REM sleep is absent
• sleep paralysis: brain exit REM to waking state but muscle paralysis persists