Lecture 9 - Sleep 2: Sleep, dreaming and memory Flashcards
EEG stands for
Electroencephalogram
EOG stands for
Electrooculogram
EMG stands for
Electromyogram
Electroencephalogram
gross brain electrical activity, generated by neurons that create synaptic potentials
Electrooculogram
eye movements, sits on muscles next to eyes and detect the activation of these muscles
Electromyogram
muscle activity, other muscles that aren’t captured on the EOG
EEG patterns as you sleep
Theta waves are at a lower frequency, change from random activity when someone is awake
As the sleeper progresses from stage 1 to stage 4 sleep the EEG becomes more synchronised and of higher amplitude
Then after a period of about 60 minutes the EEG begins to resemble the stage 1 or awake state, muscle tone decreases and the eyes start moving rapidly
Muscle tone decreasing means that you become very relaxed
Synchrony suggests that neurons are all firing together which means that there is the potential for larger potentials when all the neurons are firing at the same time (summate)
Yellow graph shows that there are small REM periods initially and then throughout the night the length of the REM periods increases
Awake
low voltage, high-frequency beta waves
Drowsy
Alpha waves prominent
Stage 1 sleep
Theta waves prominent
Stage 2 sleep
Sleep spindles and mixed EEG activity
Slow wave sleep (stage 3 and stage 4 sleep)
Progressively more delta waves (stage 4 shown)
REM sleep graph
Low voltage, high-frequency waves
EOG detects rapid eye movements
EMG shows loss of muscle tone
REM sleep
Rapid eye movement sleep is a unique phase of sleep, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.
Also known as paradoxical sleep
High correlation with dreaming
80% report dreaming during REM, 7% report dreaming during slow wave sleep
Dream = a holistic mental experience (some would say hallucination) while asleep consisting of characters interacting over a period of time in a succession of several organised and apparently real, although bizarre, vivid images or scenes
Lower chance of vivid dreams when waking someone from slow wave sleep
Slow wave sleep
Slow-wave sleep (SWS) refers to phase 3 sleep, which is the deepest phase of non-rapid eye movement (NREM) sleep, and is characterized by delta waves (measured by EEG). Dreaming and sleepwalking can occur during SWS. SWS is thought to be important for memory consolidation.
Common beliefs about dreams - External stimuli can be incorporated into dreams
Plenty of information to back this statement up therefore it is true
Such as parents being able to hear their young children crying when they are seemingly in a deep sleep
Common beliefs about dreams - dreams last only an instant
Usually people guess their dream duration is similar to the amount of time they were in REM sleep, usually consistent with external time therefore this statement is false
Common beliefs about dreams - Some people do not dream
Some do not dream due to pathology but most of the time it is because people do not remember their dreams, therefore this statement is false
Common beliefs about dreams - Penile and clitorial erections indicate dreams with sexual content
Does not seem to have any relation to the dream content, it is just a physiological response
In males, erections occur 3-5 times a night roughly lasting 30 mins even if they do not have a sexual dream
Therefore this statement is not necessarily true
Common beliefs about dreams - People only dream in black and white
Can test by waking people up during REM sleep
Some dreams do not have colour but by large many of them do
Common beliefs about dreams - Eye movements in REM sleep relate to dream content
REM sleep behaviour disorder is where people go into REM sleep and usually you have a decreased muscle tone but for people with this disorder this does not occur so people start acting out their dreams and the eye movements in these cases corresponds to what is occurring in these people’s dreams
This statement is therefore possibly correct
Common beliefs about dreams - If you fall in your dream and hit the ground, you will really die
Only people that would know if this statement is true are dead people….
Plihal and Born (1977)
Paired associate word list (explicit memory) and Mirror drawing (procedural memory) tested after REM and SWS. Explicit tasks improved by SWS
Procedural memory enhanced by REM
Learn at 11pm and test after 3 hours sleep (get early sleep) OR sleep 3 hours, learn at 2 am, sleep and test at 5am (get late sleep) OR control participants stay awake during the interval
Percent improvement = performance improvement, higher up you are the better you perform
These studies suggests that: declarative memory is enhanced by early (slow wave sleep?) sleep and that procedural memory is enhanced by late (REM?) sleep
Wagner et al. 2004
The scientists provided the subjects with two rules by which to generate a second string of numerals. In addition, a shortcut, which the researchers did not divulge, could be used to arrive at the target answer. After initial training, some participants were allowed to get a good nights sleep while others remained awake. When they returned to the problem eight hours later, those who had slumbered were twice as likely to find the shortcut as were those who hadnt slept. Members of a second group that trained in the morning and attempted the problem again later that day were also slower at finding the shortcut, suggesting that tiredness was not a factor for the poor performances.
Participants presented with a sequence completion task before (training) and after (test) sleep or control condition
On each trial, a different string of eight digits was presented
Each string was composed of the digits 1, 4 and 9 e.g. 1 1 4 4 9 4 9 4
For each string, subjects had to determine what the final digit was
A solution could be arrived at by computation or insight
Computation : two simple rules
The ‘same rule’ - the result of two identical digits is just this digit
The ‘different rule’ - the result of two non-identical digits is the remaining third digit
Insight = the 2nd digit is always the same as the last Blocks = blocks of training
Experiment suggests that whilst you are asleep and not necessarily conscious of what it going on around you, sleep can help you think about problems going on in the world around you whilst asleep (the brain is training to solve them)
