Lecture 17 EEG Flashcards
(24 cards)
What is Electroencephalography (EEG)?
A method of detecting neural activity by placing electrodes on the scalp
What do the electrodes in EEG detect?
Small fluctuations of electrical signals, originating from activity of mostly cortical neurons
How is the EEG signal related to cognitive processes?
The raw signals are systematically related to cognitive processes, allowing us to learn about cognition during tasks
What is the principle of EEG measurement?
Electrical currents flow from high to low voltage, measuring current flow from the scalp to the ground
Is EEG recording invasive or non-invasive?
Non-invasive
Who first detected the EEG signal and when?
Hans Berger in 1924
What technique did Hans Berger initially use to record EEG signals?
Two electrodes – silver wires placed under the scalp
What is the characteristic frequency of the alpha rhythm described by Berger?
8-13 Hz
What happens in EEG when eyes are closed?
Increased amplitude but decreased frequency
What is applied to decrease impedance between the scalp and electrode?
Electrode gel/paste
What is the typical amplitude range of EEG signals?
10 μV to 100 μV
By what factor are EEG signals typically amplified?
1,000 to 100,000
What types of frequencies are removed from the EEG signal during processing?
- Low frequencies (<0.5-1 Hz)
- High frequencies (>35-70 Hz)
What is the purpose of notch-filtering in EEG?
To remove line noise, typically at 50 Hz or 60 Hz
What strong artifacts can contaminate EEG signals?
Eye movements & Eye blinks
What causes the EEG activity?
Post-synaptic potentials arising from neurotransmitter binding to receptors
What determines the sign of the recorded potentials in EEG?
The orientation of the neurons
What is the functional unit of EEG activity?
> 10,000 simultaneously activated neurons
What is the main source of EEG signals?
Large cortical pyramid cells
Why are signals in the sulci harder to detect?
They are masked by signals from the gyri
What is a mathematical challenge in locating EEG signal sources?
It is an inverse problem with multiple dipole solutions possible
What does the EEG signal we measure consist of?
A mixture of many frequencies plus noise from different brain locations
What method allows us to measure amplitude changes in EEG during cognitive tasks?
Event-related potential (ERP) method
What is the purpose of a spectrogram in EEG analysis?
**To identify dominant frequencies and their timing in the EEG signal
