Consciousness and the Brain
- The Reticular Activating System (RAS) controls consciousness. When stimulated, the brain wakes up. When inhibited, you sleep.
- Biological Rhythms: period fluctuations in a biological system.
- Affect urine volume, blood pressure, etc.
- Can be affected by time, daylight, temperature, etc.
- Circadian Rhythms: rhythms that happen every 24 hours.
- Example: sleep/wake cycle.
- Suprachiasmatic nucleus (SCN): biological clock, located in hypothalamus
- Sensitive to change in light
- Jet lag is when sleep/wake patterns are out of sync with temperature and hormone cycles.
- Women retroactively assign more mood swings to their menstrual cycle than in-the-moment journals they write actually attest to
Stages of Sleep
As you fall asleep:
- Beta waves (awake)
- Alpha waves (relaxed, eyes closed)
This sequence takes 30-45 minutes:
- Stage 1: small and irregular brain waves, you drift into light sleep.
- Stage 2: the brain emits occasional short bursts of rapid high-peaking waves called sleep spindles, and other waves called K-complexes.
- Sleep spindles are related to memory and learning.
- K-complexes respond to sound but let you keep sleeping if the sound isn’t a threat.
- Stage 3/4: brain emits delta waves (very slow waves with very high peaks). Muscles are relaxed. Deep sleep.
Then you go from Stage 3/4 to 2 to 1. Then you enter REM sleep: the brain is extremely active but the body is not.
- REM = fast, low-amplitude, high-frequency waves.
- During REM, muscles are paralyzed so you don’t act out your dreams.
REM/non-REM cycles go back and forth for the night, with REM periods getting longer and closer together.
Why We Sleep
- Sleep conserves energy.
- Sleep restores the body.
- The brain washes itself with cerebrespinal fluid (CSF).
- Amyloid lata, a protein that builds up in the hippocampus and thalmus, is removed
- Helps with learning and memory.
- Sleep apnea: breathing ceases for a moment while the person is sleeping.
- Can cause high blood pressure and irregular heartbeat.
- Narcolepsy: person lapses into 5-30 mins of REM sleep during the day.
Benefits of sleep
- Sleep is crucial for consolidation, where synaptic changes associated with recently stored memories become durable and stable.
- One theory is that the neurons activated during the original experience are re-activated, consolidating the memory and moving it from the hippocampus to long-term storage in the cortex.
- Dreams can reflect ongoing problems in life.
- Dreams can be modifications of thinking activity that happens during the day.
- Activation-synthesis theory: dreams can the result of neurons firing in the lower part of the brain (pons) during REM sleep, and then they are interpreted despite having no meaning.
- The brain creates meaning where there is none.
Why we forget dreams
The cortical neurons that control the initial storage of new memories are turned off during sleep, so we often can’t remember dreams for very long.
Hypnosis is in the expectations: if you tell them that pedaling on a bike will hypnotize them, it may work.
- Some people are more responsive / accepting of hypnosis than others, and it works better on them.
- Hypnosis can boost the amount of memories recalled, but also increases errors.
- Hypnosis has been used to treat pain, anxiety, obesity, asthma, etc.
Modern theory of hypnosia: the system in the brain that interprets information hands over its function to the hypnotist, and takes its instructions on how it should interpret the world and act in it.
- A lot of forms of meditation want to get you to “restful alertness”.
- Mindfulness-Based Stress Reduction (a popular type of meditation that’s often studied) has been shown to lower stress.
- Meditation increases gray matter in the brain, and decreases amygdala activation.
- ikely a lot of benefits associated with meditation result from the lowered stress.
- Stimulants speed up activity in the central nervous system.
- Depressants slow down the central nervous system, and make someone calm or drowsy.
- Alcohol suppresses parts of the brain that normally inhibit behavior.
- Opiates relieve pain, and have the same effect on the brain that endorphins do.
- Psychadelics disrupt normal thought processes, such as the perception of time and space.
The effects of a drug can also depend on:
- Past experiences with the drug (and whether they were positive/negative).
- Circadian rhythms / time of day when drug is taken.
- Emotional setting (at home vs. at a party).
- Motives for taking a drug.