Electroencephalography (EEG) Questions With Solutions
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Course
Electroencephalography
Institution
Electroencephalography
Electroencephalography (EEG) Questions
With Solutions
Who initially invented EEGs? Hans Berger detected the first EEG signal in 1924 with
electrodes attached to the scalp of a human and reported the results in 1929.
Berger initially studied medicine because he was convinced that there is "ps...
Electroencephalography (EEG) Questions
With Solutions
Who initially invented EEGs? Hans Berger detected the first EEG signal in 1924 with
electrodes attached to the scalp of a human and reported the results in 1929.
Berger initially studied medicine because he was convinced that there is "psychic energy", which
might allow for telepathy.
Berger also first described the alpha rhythm - when people closed their eyes, the electrical signal
was not constant, but it varied with a characteristic frequency of 8-13 Hz.
Initially, he used two electrodes, one attached to the front of the head and one to the rear and
recorded the potential (i.e. voltage) difference between them.
Describe the neurophysiology of an EEG. The EEG activity does not reflect action
potentials but originates mostly from post-synaptic potentials - voltages that arise when
neurotransmitters bind to receptors on the membrane of the post-synaptic cell
This causes ion channels to open or close, leading to graded changes in the potential across the
membrane
This can be understood as a small "dipole"
Signals from single cells are not strong enough to be recorded outside of the head, but if many
neurons spatially align, then their summed potentials add up and create the signals we can record
This pooled activity from groups of similarly oriented neurons mostly comes from large cortical
pyramid cells
, Electroencephalography (EEG) Questions
With Solutions
What are some limitations of EEGs? EEG is biased to signals generated in superficial
layers of cerebral cortex on the gyri (ridges) directly bordering the skull.
Signals in the sulci are harder to detect than from gyri, and may additionally be masked by the
signals from the gyri.
The meninges, cerebrospinal fluid (CSF) and skull "smear" the EEG signal, making it difficult to
localise the source.
What is the inverse problem in relation to EEG signals? Mathematically, if the sources are
known, the resulting scalp configuration of signals can be reconstructed; however, the reverse is
not true - one given scalp configuration of signals can have multiple dipole solutions!
What are the four steps in analysing EEG data? 1. The signal
2. Processing of the data
3. Artefacts
4. Measurements
Describe the first step of analysing EEG data (the signal). EEG signals measured from the
scalp in relation to a reference electrode.
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