The EEG(Electroencephalogram)

Jason Konold and Gero Kassing

A Short History• 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)

Hans Berger

How It Works

Large-Scale Neuron Action

• Neurons (brain cells) become charged when

active.

• The electrodes are simply 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

Neurons

A Typical Clinical Session• They usually last 20-30 minutes.

• Electrodes are placed on the scalp

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

• Patient conducts activities to generate responseso Hyperventilating

o Photic stimulation (this is simply a fancy way of saying “shine a light in their

face”

o Sleep (or sleep deprivation)

o Mental excercises

10-20 System

Naming the Electrodes• In the 10-20 System, electrodes are given a letter

corresponding to which lobe they are placed on… o P- Parietal

o T- Temporal

o O- Occipital

o F- Frontal

• …or a letter based on general positioning o Fp- Frontopolar

o C- Central

o 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

For ExampleRight hemisphere,

first electrode in

auricular area,

therefore it receives

the name A2

Electrocorticography(ECoG)

• In some cases, electrodes may be inserted into the

skull

• Also known as subdural or intracranial EEG (SD-EEG

or I-EEG)

• This procedure is sometimes used in the case of

patients with epilepsy

Advantages &Disadvantages

Advantages• EEG costs significantly less

• Is much more portable

• Does not expose patients to magnetic fields or x-rays

• Is silent – this is important when studying reactions to audio

• You don’t have to go into a tube which may get uncomfortable to some people

• Not stuck by a needle which may also be uncomfortable to some people

• Sticky electrodes are plastered all over your head

• Poor resolution

• Most sensitive to post-synaptic potentials – cortex

• Large areas of the cortex have to be activated for the electrodes to register anything on the skull

• The 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

Disadvantages

References

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.htm

Brain neuron forest. (n.d.). Alzheimer's association. Retrieved October 30, 2013, from http://www.alz.org/braintour/neuron_forest.asp

Electroencephalography. (2013, October 29). Wikipedia. Retrieved October 31, 2013, from http://en.wikipedia.org/wiki/Electroencephalography

Law, 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.html

Mathias, R. (1996, December 1). The basics of brain imaging. NIDA notes. Retrieved October 30, 2013, from http://archives.drugabuse.gov/NIDA_Notes/NNVol11N5/Basics.html

Schachter, 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.full

What is Electroencephalography (EEG). (2013, February 1). Mega Electronics Ltd RSS. Retrieved October 31, 2013, from http://www.megaemg.com/knowledge/electroencephalography-eeg/