Consciousness is awareness of our self and environment – dif levels of awareness can be induced by external factors such as drugs or internal mental efforts. Range from alertness to sleep.
Alertness – you’re awake
Daydreaming– feel more relaxed, not as focussed. Can also be light meditation (self-induced)
Drowsiness – just before falling asleep/after waking up. Can also be self-induced in deep meditation.
Sleep – not aware of world around you.4 main types (Each type oscillates at dif frequency)
Alpha waves (8-13 Hz) – in daydreaming. Disappear in drowsiness but reappear in deep sleep. During relaxation.
Theta waves (7 Hz) – Drowsiness, right after you fall asleep.
Delta waves (0.5-3 Hz) – Deep sleep or coma.
EEGs can measure brainwaves
Sleep Stages and Circadian Rhythms
Your brain goes through distinct brain patterns during sleep. 4 main stages that occur in 90 min cycles
(Order is from N1 -> N2 -> N3 -> N2 -> REM – Order within cycle goes How long each stage lasts depends on how long you’ve been asleep and your age)
First is non-rapid eye movement sleep (non-REM) – N1, N2, N3
N1 (Stage 1)– Dominated by theta waves. Strange sensations – hypnagonic hallucinations, hearing or seeing things that aren’t there.
Seeing flash of light, or someone calling your name, doorbell, etc. Or the Tetris effect – if you play Tetris right before bed, you might see blocks. Also a feeling of falling – hypnic jerks. Theta waves.
N2 (Stage 2)– deeper stage of sleep. People in N2 are harder to awaken. We see more theta waves, as well as sleep spindles andK-complexes.
Sleep spindles help inhibit certain perceptions so we maintain a tranquil state during sleep. Sleep spindles in some parts of brain associated with ability to sleep through loud noises.
K-complexessupress cortical arousal and keep you asleep. Also help sleep-based memory consolidation. Even though they occur naturally, you can also make them occur by touching someone sleeping.
N3 (Stage 3) – slow wave sleep. Characterized by delta waves. Where walking/talking in sleep happens.
REM (rapid-eye movement) stage. Most of your other muscles are paralyzed. Most dreaming occurs during REM sleep, so paralysation inhibits actions. Most important for memory consolidation.
Combination of alpha, beta, and desynchronous waves, similar to beta waves seen when awake.
Sometimes called paradoxical sleep, because brain is active and awake but body prevents it from doing anything.
Waking up during REM sleep prevents memory formation of the dream.
Circadian Rhythms – why you get sleepy in afternoon. They’re our regular body rhythms across 24-hour period. Controlled by melatonin, produced in the pineal gland.
Control our body temperature, sleep cycle, etc.
Daylight is big queue, even artificial light.
Also change as you age – younger people are night owls, but older people go to bed early.
Dreaming
Everybody dreams during REM sleep. Can tell someone is dreaming because eyes are moving rapidly under eyelids, and brainwaves look like they are completely awake.
Activity in prefrontal cortex during REM sleep is decreased – part responsible for logic. Why things in our things that defy logic don’t seem weird.
Sigmund Freud
Dreams are our unconscious thoughts and desires that need to be interpreted. Little scientific support.
Evolutionary biology
Threat simulation, to prepare for real world.
Problem solving
No purpose
Other
Maintain brain flexibility
Consolidate thoughts to long-term memory, and cleaning up thoughts. People who learn + sleep retain more than those who do not sleep. But role of REM is unclear.
Preserve and developing neural pathways. Because infants constantly developing new neural networks spend most of time in REM sleep.
Dream Theories – Freud and Activation Synthesis Hypothesis
Do our dreams have a meaning? Sigmund Freud’s theory of dreams says dreams represent our unconscious feelings/thoughts. Like an iceberg.
What happens? Manifest content (Ex. Monster chasing you)
What is hidden meaning? Latent content (Ex. Job pushing you out)
Can help us resolve and identify hidden conflict.
Activation Synthesis Hypothesis
Brain gets a lot of neural impulses in brainstem, which is sometimes interpreted by the frontal cortex.
Brainstem = activation, and cortex = synthesis.
Our brain is simply trying to find meaning from random brain activity. Therefore might not have meaning.
Sleep Disorders
People with sleep deprivation might be more irritable and have poorer memory. Could be dangerous when it comes to flying airplanes or driving cars.
Also more susceptible to obesity – body makes more cortisol, and the hunger hormone.
Can also increase your risk for depression. REM sleep helps brain process emotional experiences, which can help protect against depression (not certain).
Can get back on track by paying back “sleep debt”
How much is enough sleep? 7-8 hours for adults. Varies with age and individual. Babies need a lot more.
More serious form – insomnia (persistent trouble falling asleep or staying asleep). Various medications but taking them too long leads to dependence and tolerance.
Exercising or relaxing before bed can help
Other end of spectrum is narcolepsy – can’t help themselves from falling asleep. Various fits of sleepiness, going into REM sleep. Can occur any time. 1 in 2000.
Indications it’s genetic, and linked to absence of alertness neurotransmitter.
Sleep apnea – 1 in 20 people. People with it are often unaware. Stop breathing while sleeping – body realizes you’re not getting enough oxygen, wake up just long enough to gasp for air and fall back asleep without realizing. Can happen 100x/night!
Don’t get enough N3 (slow-wave) sleep.
Snoring is an indication, or fatigue in morning.
Sleepwalking/sleep talking – mostly genetic, occur during N3 and are harmless. Occur more often in children (have more N3).
Breathing-Related Sleep Disorders
Sleeping problems can arise from brain, airways, or lungs/chest wall.
Obstruction to airways causes problems breathing at night
Air going into nose/mouth reaches the lungs. Tissues around neck may block this airflow – snoring/gasping/pauses in breathing. Called an apnea (absence of airflow).
Called obstructive sleep apnea, very common and gets worse as people get older.
People are tired/sleepy and unrefreshed when they wake up.
5+ apneas an hour (measured by polysomnography)
In the brain, called central sleep apnea. Presence of apneas without obstruction. Problem with the control system for ventilation.
Cheyne-Stokes breathing (period of oscillations, then flat, etc.) pattern in polysomnography
In lungs or chest wall, hyperventilation can occur (high pCO2, low pO2). Caused by medication/obesity. Chronically elevated pCO2 can lead to right-sided heart failure.
Hypnosis and Meditation
Hypnotism usually involves getting person to relax and focus on breathing, and they become more susceptible to suggestion in this state – but only if they want to. More alpha waves in this stage – an awake but relaxed state.
Some use hypnosis to retrieve memories, very dangerous because memories are malleable. Can create false memories.
2 theories for how it works:
Dissociation Theory – hypnotism is an extreme form of divided consciousness
Social Influence Theory – people do and report what’s expected of them, like actors caught up in their roles
Refocused attention, so sometimes it’s used to treat pain. Reduced activity in areas that process sensory input. Although it doesn’t block it out, it might inhibit attention
Meditation – training people to self-regulate their attention and awareness. Can be guided and focused on something in particular, like breathing, but meditation can also be unfocussed – mind wanders freely.
More alpha waves than normal relaxation in light meditation.
In deep meditation have increased theta waves in brain.
In people who regularly go to deep meditation, increased activity in prefrontal cortex, right hippocampus, and right anterior insula – increased attention control (goal of meditation).
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