EEG And Sleep Flashcards
What does EEG stand for?
Electroencephalogram
What does EEG measure
Electrical activity of the brain, more specifically the synchronicity of firing of the pyramidal neurones in the brain - does not measure one neurone but a collection of neurones which all do the same thing.
Amplitude of the waves measured depends on how synchronised the activity is - the more synchronised the activity the larger the waves
Measuring through the scalp and bone and meninges
What do EEG readings mean
Electrical activity in different areas of the brain
Can show different areas of activation at different times
Function of different areas depending on the activity in that area depending on what you are doing.
What makes the neurones fire synchronously
Pace maker - thought to be the thalamus. As they have an intrinsic rhythm
Also coordinated networks. Lots of sensory input into the thalamus leads to collective interaction
Thought the thalamic pacemakers and coordinated networks work together to cause synchronous activity
Normal synchronous activity
Learning- binding phenomena whereby brain sees something that was not previously there and now cannot be unseen due to the connections in the brain
Fastest oscillations are seen in learning - as we attach meaning to our world
Sleep - synchronous firing deep sleep larger peak larger synchronicity
Pathological synchronicity
Epilepsy
What is sleep?
Become insensible
Decreased mobility
Decreased responsiveness to sensory inputs
Decreased cortical excitability in EEG
Readily reversible state unlike a coma or under GA
Necessity of sleep
All mammals and birds - evolutionarily important,
Spend 1/3 of your life sleep
Motivated behaviour not a stereotyped reflex response.
Not always the same depends on the external and internal stimuli cause sleep to happen
Functions of sleep
Recuperation and energy conservation
Cognitive functions
Important in mood
Altered physical health - immune suppression and metabolic pathways
Stages of sleep
Beta - rem Alpha - relaxed reflecting Theta - drowsy idealing Delta - deep dreaming Delta - deep dreamless
What happens in R.E.M sleep beta
Desynchronised EEG activity - similar recording to being awake but loss of muscle tone
Rapid eye darting
Easily aroused by meaningful stimuli
Awakened are alert
Dreaming - dreams can be other stages too but they are different
Loss of muscle tone
Is there a sleep wake centre
Reticular activating system in midbrain and thalamus
Current view is that there are 2 major groups of neurones
Ach
Monoamine
When active they activate thalamic relay neurones resulting in cortical activation
When Ach and monoamine active you are awake
When only Ach active you are R.E.M. Thought monoamine important in loss of muscle tone.
Is sleep the absence of wakefulness
NO
Non-R.E.M. Sleep nuclei in the brainstem are less active but the VLPO - ventrolateral preoptic area in the hypothalamus is more active when asleep than when awake so this area makes you actively sleep.
What is the flip flop theory
States that there is no in between when it comes to sleep you are ever asleep or awake.
What induces sleep?
Waking time - adenosine accumulation over the day
Evidence caffeine - an adenosine receptor antagonist so adenosine cannot have its effect therefore cannot induce sleep
Also exercise makes you sleep earlier not longer - this means that the more accumulation of adenosine due to the exercise makes you tired faster
Circadian rhythm - suprachiasmatic nucleus in the hypothalamus- Zietgeber time giver - detect the light at the retina and a decrease in light = sleep so you can see how long is left in the day - sleep
Neurones -‘tick’ relates to protein synthesis/ degradation pattern in a 24hr cycle - this is jet lag body telling you it’s night but your suprachiasmatic nucleus tells you is is day so there is a conflict
