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The EEG(Electroencephalogram)

Jason Konold and Gero Kassing

One of the older methods of brain scanning

1875, Richard Caton presented findings of electrical phenomena in the brains of rabbits and monkeys

1912, Vladimir Vladimirovich Pravdich-Neminsky created the first animal electroencephalogram

1924 First human electroencephalogram recorded by Hans Berger (he also named it)

A Short History

Hans Berger

{How It Works

Neurons (brain cells) become charged when active The electrodes are sensors that detect changes in

electrical charge A single neuron becoming charged cannot be detected

by an EEG, so the EEG measures large groups of neurons acting simultaneously

Large-Scale Neuron Action

Neurons

Usually last 20-30 minutes Electrodes placed on the scalp

The standard placement is in the “10-20 System” or “International 10-20 System”

Patient conducts activities to generate responses Hyperventilating Photic stimulation (a fancy way of saying “shine a light

in their face”) Sleep (or sleep deprivation) Mental exercises

A Typical Clinical Session

10-20 System (of electrode placement)

In the 10-20 System, electrodes are given a letter corresponding to which lobe they are placed on…

P- Parietal T- Temporal O- Occipital F- Frontal

…or a letter based on general positioning Fp- Frontopolar C- Central A- Auricular (over the ear)

Then they receive a number based on lateral position: an odd number if on the left hemisphere and an even number if on the right

Naming the Electrodes

For ExampleRight hemisphere, first electrode in auricular area, therefore it receives the name A2

Electrodes may be inserted into the skull Also known as subdural or intracranial EEG (SD-EEG or

I-EEG) Sometimes used in the case of patients with epilepsy

Electrocorticography (ECoG)

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Advantages &

Disadvantages

EEG costs significantly

less Is much more portable no exposure to

magnetic fields or x-rays Is silent – this is

important when studying reactions to audio

Advantages

No claustrophobia No needles

Sticky electrodes Poor resolution Most sensitive to post-

synaptic potentials – cortex

Disadvantages

Large areas of the cortex have to be

activated for the electrodes to register anything on the skull

Uncountable number of activity of neurons tells us what parts of the brain are active, but not enough to make an exact conclusion to the localization

Alivanit. (1998, November 27). Advantages of EEG in Comparison to High Technology Brain Imaging Methods. EEG Manual. Retrieved October 31, 2013, from http://www.aha.ru/~geivanit/EEGmanual/Advantages.htmBrain neuron forest. (n.d.). Alzheimer's association. Retrieved October 30, 2013, from http://www.alz.org/braintour/neuron_forest.aspElectroencephalography. (2013, October 29). Wikipedia. Retrieved October 31, 2013, from http://en.wikipedia.org/wiki/ElectroencephalographyLaw, A., & Halkiopoulos, C. (2010). The biological level of analysis. Psychology: developed specifically for the IB diploma (pp. 40 - 41). Oxford, U.K.: Pearson Education.Lemke, S. (1999, November 1). History. Department of psychiatry and psychotherapy. Retrieved October 30, 2013, from http://www.psychiatrie.uk-j.de/ Geschichte.htmlMathias, R. (1996, December 1). The basics of brain imaging. NIDA notes. Retrieved October 30, 2013, from http://archives.drugabuse.gov/NIDA_Notes/NNVol11N5/Basics.htmlSchachter, S. (2006, December 15). How to read an EEG. Epilepsy. Retrieved October 31, 2013, from http://www.epilepsy.com/epilepsy/eeg_read

Smith, S. (n.d.). EEG in the diagnosis, classification, and management of patients with epilepsy. -- Smith 76 (suppl 2): ii2. Retrieved October 31, 2013, from http://jnnp.bmj.com/content/76/suppl_2/ii2.fullWhat is Electroencephalography (EEG). (2013, February 1). Mega Electronics Ltd RSS. Retrieved October 31, 2013, from http://www.megaemg.com/knowledge/electroencephalography-eeg/

References