EEG Flashcards
Hans Berger - German psychiatrist
1929- Possible to record the brain’s electrical activity
Discoverer of alpha wave, known as the “Berger wave”
What is the alpha wave?
8-12 Hz activity
State of relaxed wakefulness
The target wave for meditation
What are neural generators of the EEG?
What does summated mean?
Summated current flow of synchronously activated EPSP and IPSP of pyramidal cells in the cerebral cortex
Average- events time locked to a stimulus
What does EPSP mean?
Excitatory post synaptic potentials
What does IPSP mean?
Inhibitory post synaptic potentials
EPSP and IPSP are…
What does that mean?
Ex?
Graded potentials
Response dependent on intensity of the stimulus
(Not the same size across the board)
touch gently vs. prick intensity
Pyramidal cell
Oriented perpendicular to the cortex
Pyramidal cells in the cortex have the right properties:
For brain activity to be detected through skull, must be strong signal summed over many neurons:
All behaving similarly at same time
All oriented in same way
So negative and positive don’t cancel each other out when summed
Single pyramidal cell in cortex:
Diagram (top to bottom)
Axons from presynaptic cells
Apical dendrite
Cell body
Basal dendrites
Postsynaptic cell axon
Equivalent current dipole-
Equivalent to the sum of individual dipoles
Microvolt
Millionth of a volt
EEG ratio
low signal to noise ratio (lots of noise)
Why is it important for pyramidal cell to be oriented perpendicular to the cortex?
If parallel to the surface of the brain, signal will be flat
(Positive and negative will cancel each other out, won’t pick up a signal)
Pyramidal cells:
Not all electrical fields generated by the brain are…
Strong enough to be spread all the way the scalp surface
What can be measured from the outside?
Primarily the synchronized activity of pyramidal neurons in cortical brain regions
Where can pyramidal cells be found?
In all cortical areas (occipital, temporal, parietal, frontal cortices)
How are pyramidal cells oriented?
Perpendicular to the cortical surface
What does orientation of the cells generate?
Cells in deeper brain structures…
An electrical field
Don’t have this specific orientation
These electrical field are more likely to…
Spread into various directions and cancel out instead of projecting in a stable way towards the scalp surface
What are pyramidal cells ideal to do?
Read brain’ electrical activity- recorded at scalp
Synchrony
High voltage, low frequency
Characteristic of slow wave sleep or coma
Neurons fire slowly
Desynchrony
Low voltage, high frequency EEG activity
Characteristic of arousal
Neurons fire rapidly, not together
