how do we measure brain rhythmicity?
an electroencephalogram (EEG)
what does an electroencephalogram (EEG) involve?
non invasive electrodes placed on standard positions on the head and connected to amplifiers and a recording device
what are electroencephalogram (EEG)’s used for?
diagnose certain neurological disorders
e.g. seizures in epilepsy
what does an electroencephalogram (EEG) measure?
the combined activity of a large number (1000s) of similarly orientated neurons
- summed post-synaptic activity
- requires synchronous activity across groups of cells
what does the amplitude of an EEG signal depend on?
how synchronous the activity of the neurons is
what happens when a group of cells is excited?
the tiny signals sum to generate a large surface signal
-the same amount of excitation can occur, but at irregular intervals, resulting in a small summed signal
what do EEG rhythms correlate with and how are they categorised?
- correlate with states of behaviours
- categorised by their frequency range
alertness and waking has what EEG rhythm?
high-frequency low-amplitude
non-dreaming sleep or coma has what EEG rhythm?
low-frequency high-amplitude
2 ways synchronous brain rhythms are generated?
pacemaker
-synchronous rhythms led by a central clock/pacemaker (e.g. thalamus)
collective behaviour
-synchronous rhythms arise from the collective behaviour of cortical neurons themselves
how can the thalamus act?
as a pacemaker
pacemaker behaviour, how is each individual thalamic neuron forced to conform to the rhythm of the group?
synaptic connections between excitatory and inhibitory thalamic neurons
the thalamus passes coordinated rhythms onto where?
the cortex by thalamocortical axons
a relatively small group of centralised thalamic cells can do what?
can compel a much larger group of cortical cells
with collective behaviour, how does synchronous coordinated activity happen in the neurones?
excitatory and inhibitory interconnections of neurons
-can remain localised or spread to larger regions of the cortex
name the 3 functional states of the brain
- Wakefulness
- non-REM sleep
- REM sleep
describe non-REM sleep
body capable of involuntary movement, rarely accompanied by vivid, detailed dreams
- “Idling brain in a moveable body”
- low frequency high amplitude
- occasional voluntary movement
- logical repetitive thoughts
describe REM sleep
body immobilised, accompanied by vivid, detailed dreams
- “An active, hallucinating brain in a paralysed body”
- Low-amplitude, high frequency - just like when awake
- vivid bizarre thoughts
- muscle paralysis
explain what happens to temperature, heart, rate, breathing during non-REM and REM sleep
temperature, heart rate and breathing all decrease
- temp decreases more in REM sleep
- HR and breathing decrease more in non-REM sleep
brain energy consumption in REM vs non-REM sleep
brain energy consumption decreases in non-REM sleep
INCREASES massively in REM sleep
what does each night begin with and what happens as night progresses?
- each night begins with a period of non-REM sleep
- as night progresses, there is a shift from non-REM to REM sleep
how often are sleep cycles repeated throughout the night?
every 90 minutes
purpose of sleep?
- restoration and adaptation
- sleep means we can rest and recover
- sleep means we can protect ourselves and conserve energy
what happens during wakefulness?
there is an increase in brainstem activity, and several sets of neurones in increase their rate of firing in anticipation of waking to enhance the wake state
-ACh, 5-HT, NA and histamine
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neurons and glia19
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glutamate21
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GABA and glycine27
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Monoamines52
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Neurohormones29
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Vision48
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sleep40
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intro to neuroscience40
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motivation38
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chemical senses45
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learning and memory36
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control of movement25
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auditory and vestibular system39
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structure of CNS minty8
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somatosensation I27
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somatosensation II23
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depression39
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emotion36
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schizophrenia44
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anxiety28
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language27
