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Electroencephalography (EEG) Exam
Questions and Answers 100% Pass
What is an EEG (electroencephalograph)? - ✔✔Electroencephalography (EEG) is a method of detecting
neural activity by placing electrodes on the scalp.
EEG recorded at the scalp is non-invasive - however, it is also possible to record intra-cranial EEG by
measuring activity directly at the exposed cortex.
EEG is cheap and (relatively) easy to conduct.
The temporal resolution of an EEG is great, but the spatial resolution is poor.
What is the EEG used for? - ✔✔We can use the signals from EEGs to learn something about cognition
when people perform tasks.
How does an EEG work? - ✔✔The electrodes placed on the scalp pick up small fluctuations of electrical
signals, originating from activity of (mostly cortical) neurons.
While the raw signals recorded are very noisy and might not look like much, they are systematically
related to cognitive processes.
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.
Author. Emily Charlene, ©2025 All Rights Reserved.
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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
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!
Author. Emily Charlene, ©2025 All Rights Reserved.
Electroencephalography (EEG) Exam
Questions and Answers 100% Pass
What is an EEG (electroencephalograph)? - ✔✔Electroencephalography (EEG) is a method of detecting
neural activity by placing electrodes on the scalp.
EEG recorded at the scalp is non-invasive - however, it is also possible to record intra-cranial EEG by
measuring activity directly at the exposed cortex.
EEG is cheap and (relatively) easy to conduct.
The temporal resolution of an EEG is great, but the spatial resolution is poor.
What is the EEG used for? - ✔✔We can use the signals from EEGs to learn something about cognition
when people perform tasks.
How does an EEG work? - ✔✔The electrodes placed on the scalp pick up small fluctuations of electrical
signals, originating from activity of (mostly cortical) neurons.
While the raw signals recorded are very noisy and might not look like much, they are systematically
related to cognitive processes.
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.
Author. Emily Charlene, ©2025 All Rights Reserved.
, 2|Page
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
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!
Author. Emily Charlene, ©2025 All Rights Reserved.
