EEG Flashcards
What is EEG?
Measurement of electrical activity from the brain using electrodes located on the scalp
What do the electrodes measure?
voltage fluctuations
directly result from flow of ions across cell membranes
What do electrodes look like?
metal contact discs
0.7-1.0cm diameter
They connect to a powerful amplifier
digitizes signals and conveys them to a processing computer
Who created EEG?
Hans Berger
1873-1941
What are post synaptic potentials?
where action potential reaches axon terminal and releases neurotransmitter
this diffuses across synapse
binds to receptor on PSN
becomes depolarised
causes voltage change (PSP)
What does EEG mainly show?
post synaptic potentials of pyramidal neurons
What are Pyramidal neurons?
spatially aligned and perpendicular to the cortical surface
What is ongoing brain activity characterised by?
fluctuating local field potentials
measured as changes in voltage
What does each line on an EEG recording represent?
the oscillating voltage occuring underneath the electrode
What is brain computer interface (BCI)?
direct pathways of communication between the brain and some external device
What are the principles of BCI?
activation of neurons forms a pattern and this can be studied using signal processing methods
brain communication relies on PSPs which cause local field potential - can be detected in real time
What does BCI bypass?
the brains normal pathways
What are output BCIs?
devices that convert human intentions in form of electrophysiological signals to overt device control
What are input BCIs?
devices that translate external stimuli such as light or sound into internally perceived visual or auditory perceptions e.g cochlear implant
What are non-invasive BCIs?
typically include equipment that can sense changes in brain activity in real time
e.g EEG
What are invasive systems? (ECoG)
electrodes that can be implanted on top of relevant cortex such as motor regions to record activity from specific parts of brain
ECoG = Electrocorticography
What is another example of an invasive system?
Microelectrodes
tiny array of needle electrodes inserted into brain tissue to record field potentials directly as they occur
