The mind is adaptive II
• What is sleep?
Many brain regions are more active during sleep than during wakefulness.
During sleep, the brain is still active. Sufficient sleep is important for the
• Sleep is an Altered State of consciousness.
When you sleep, you are not conscious, but your brain still processes
information and, to some extent, remains aware of your environment. When
people are awake, their brains neurons are extremely active, as evidenced
by short, frequent, desynchronized brain signals known as beta waves.
When people close their eyes and relax, brain activity slows and becomes
more synchronized a pattern that produces alpha waves. Essentially:
Awake beta waves.
Right before you sleep alpha waves.
Sleep occurs in stages, as evidenced by changes in EEG readings:
Alert wakefulness Beta waves
Just before sleep Alpha waves
Stage 1 Theta waves
Stage 2 Sleep spindles & K-complex( L.
Stage 3 Delta waves
Stage 4 Delta waves
In stage one you can be aroused easily. In stage two your breathing slows
and you are less affected by external stimulations. Abrupt noises can
trigger k-complexes. As people age and sleep lighter, their EEGs show
fewer sleep spindles. People still process information in stage 4, as the
mind continues to evaluate the environment for potential danger.
After about 90 minutes of sleep, a peculiar thing happens. The sleep cycle
reverses, returning to stage 3 and then to stage 2. At this point, the EEG
suddenly shows a flurry of beta wave activity that usually indicates an
awake, alert mind. Rapid eye movements happen in this stage called REM
sleep (or paradoxical sleep: stage marked by rapid eye movements,
dreaming and paralysis of motor systems.).Some neurons in the brain, especially in the occipital cortex and brain stem regions, are more active
during REM sleep than during waking hours. During REM episodes, most
of the body’s muscles are paralyzed and the body shows signs of genital
arousal. The cycle repeats over the course of the night.
Insomnia is a disorder characterised by an inability to sleep. Mental
health and ability to function are compromised. Chronic insomnia is
associated with diminished psychological well-being, including feelings of
depression. Some people experience pseudo insomnia, in which they
basically dream they are not sleeping. The preferred treatment for insomnia
is cognitive-behavioural therapy, which helps people overcome their
worries about sleep. Other factors that contribute to insomnia include poor
Sleep apnea is a disorder in which a person stops breathing while asleep.
Chronic apnea causes people to have poor sleep, which is associated with
daytime fatigue and even problems such as inability to concentrate while
Narcolepsy is a sleep disorder in which people fall asleep during waking
hours. A person may experience the muscle paralysis that accompanies
REM sleep. Evidence suggests that narcolepsy is a genetic condition that
affects the neural transmission of a specific neurotransmitter in the
hypothalamus. The most widely used treatments are stimulants like
modafinil although some researchers suggest that narcolepsy is an
The opposite of narcolepsy is REM behaviour disorder, in which the
normal paralysis that accompanies REM sleep is disabled so that people
act out their dreams while they’re sleeping.
Unlike Rem behaviour disorder, sleepwalking is a relatively common
behaviour that occurs during stage 4 sleep. Technically called
somnambulism, it typically occurs within the first hour or two after falling
How to develop good sleeping habits:
- Establish a routine.
- Never consume alcohol or caffeine just before going to bed.
- Regular exercise will help maintain your sleep cycle.
- Do not spend time in your bed reading, eating, or watching television.
- Relax, do not worry.
- When you cannot fall asleep, get up and do something else. - Do not try to make up for lost sleep by sleeping late the next morning
or napping during the day.
• Sleep is an adaptive behaviour.
Some dolphin species have unihemispherical sleep. In which the cerebral
hemisphere take turns sleeping. It used to be assumed that all animals
sleep, evidence indicates that some animals never exhibit a state that can
be considered sleep. Three general explanations for sleep’s adaptiveness:
restoration, circadian cycles, and facilitation of learning.
Restoration and sleep deprivation:
The restorative theory states that sleep allows the brain and body to rest
and to repair themselves. Sleep apparently allows the brain to replenish
glycogen stores and strengthen the immune system.
In a brain imaging study, sleep-deprived people showed increased
activation of the prefrontal cortex, which suggests that some bra