Sleep, dreams and consciousness Flashcards
How does an EEG machine work
Electrodes are placed on the scalp and pick up the electric fields generated by neurons
Small voltage fluctuations are measured between selected pairs of electrodes
EEG activity when awake and attentive
Desynchronised, low-voltage high-frequency activity
Gamma and beta rhythms
EEG activity when drowsy or eyes closed
Slowed activity, alpha waves appears at 8-12Hz
EEG activity during stage 1 sleep
Theta waves (4-8Hz) and amplitude increases slightly
EEG activity during stage 2 sleep
Very sharp high-amplitude waves called K complexes, spindles (8-14Hz) in brief epochs involving synchronised thalamocortical activity
Definition of sleep
A condition that typically occurs for several hours every day, characterised by immobility, reduced response to sensory stimuli, rapidly reversible
EEG activity during stage 3 and 4 (deep sleep)
Continuous delta waves (<4Hz)
EEG activity during REM sleep
Similar to awake stage- low voltage, high frequency
Beta and gamma waves
How many times do we cycle through all the sleep stages per night
6 times a night
How do we cycle through the different stages of sleep in a night
Awake -> NREM stages 1-4->NREM stages 4-1 -> REM sleep ->NREM stages 1-4
Each cycle, deep stage sleep is reduced and REM sleep is prolonged
EOG (electrooculogram) recordings at different sleep stages
Awake- rapid eye movement
NREM- slow random eye movements
REM- rapid eye movements
EMG (electromyography) recordings at different sleep stages
Awake- continuous, voluntary
NREM- some episodic involuntary movement
REM- motor output commanded but inhibited (due to atonia)
What happens to a mouse if you keep it in complete darkness
Circadian rhythm maintained but the mice gradually wake up earlier and earlier, because the mouse’s internal clock is slightly shorter than 24 hours
What is the master pacemaker of circadian rhythms
Suprachiasmatic nucleus
What is the result if the suprachiasmiatic nucleus is removed
Circadian rhythms break down, animals show random bouts of activity and sleeping
What happens if an SCN neuron is removed and cultured so they have no input
The neuron’s gene expression patterns continue to oscillate with the circadian rhythm, but this gradually disappears
What is it called the SCN uses retinal input to synchronise the internal circadian rhythm with light-dark rhythms
Photopic entrainment of circadian rhythms
What retinal cells supply the SCN with light-dark info
RGCs
Photosensitive RGCs with melanopsin, project directly to the SCN
What determines phase phenomenon in SCN transplants
The donor animal’s circadian rhythms
eg transplanting a mouse SCN into a human would shift the human’s circadian rhythm to below 24 hours
Match height of brainstem lesions to their effect
Lesions below the pons- normal sleep/wake pattern
Mid-pons lesions- continuously awake
Lesions above the pons- permanently asleep
Why does lesioning different heights of the brainstem cause different wake/sleep disruptions
Different brainstem nuclei act as diffuse modulatory systems, regulating global activity
How does the activity of neurotransmitter released by brainstem nuclei differ across wake/sleep
ACh, serotonin, DA and NA are all most active during wake and less active during NREM sleep
ACh and DA are active during REM sleep
What is sleep homeostasis
If we don’t sleep for a while, sleep pressure builds up
If we don’t sleep for a LONG time, additional sleep pressure builds, and we sleep longer to compensate
Effects of sleep deprivation in humans- all nighter
Fatigue, irritability, impaired memory