Lecture notes
EEG brain imaging
- Institution
- University Of Portsmouth (UoP)
Document looking at EEG, the uses, how to set it up and analyse data, benefits and disadvantages.
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EEGKey Studies:
Hansberger (1920s): he was trying to prove that telepathy exists and first tried
recording the swelling in the brain with tools and so went into operating theatres to
access open skulls. He eventually wen on to using electrodes.
Gray Walter (1957): made the movement to the modern EEG and made it non-
invasive.
Notes:
The EEG aims to record the electrical activity of the brain from electrodes placed on the
scalp. It has faster temporal resolution than fMRI, PET and CAT and is non-invasive. But it
suffers in terms of spatial resolution.
History:
The first applications were used in medicine to detect brain tumours, brain
abnormalities, sleep spindles or burst suppression (linked to brain swelling, helps
decide whether an operation is needed or to provide medication. Other imaging
techniques are also common now in medicine e.g., fMRI or CT.
EEG is still used in medicine for epilepsy and psychological issues.
Setting up an EEG:
Will need: electrodes, electrode cap (10-20) system, tape measure, electrode gel
and an amplifier (to actually see the activity as when the information comes through
the scalp it is tiny).
Think about noise and access points to the scalp.
Dome electrodes go onto the face to remove that activity from the EEG e.g., facial
muscle movements, talking, blinking – this data is useful for explaining brain data
because blinking can change brain activity.
Where does the data come from?
Skull = biggest barrier
For a signal to be useful it needs to be an electrical oscillation cycle (line going up
and down) and needs to oscillate at a certain frequency (lower frequencies get
through the skull easier).
Glial cells (support and clean up): generate electrical fields that are quite stable but
don’t oscillate enough to get any data.
Neurone action potentials: shift from positive to negative (they oscillate) but at a
very high frequency so the activity is absorbed/filtered out.
Post synaptic potentials: they oscillate which can be picked up by an EEG. Made up
of inhibitory post synaptic potentials (IPSPs) and excitatory post synaptic potentials
(EPSPs) which contribute to the EEG. IPSPs and EPSPs from pyramidal cells make up
the majority of EEG signals because they all fire at the same time.
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