Electrocorticography (ECoG), also called intracranial EEG (iEEG), is a method for measuring brain activity. This method is only used with people who have had their skull opened for surgical purposes. Electrodes are placed directly on the cortex. ECoG is therefore invasive, but has a better spatial resolution than EEG and MEG.
ECoG originated in the 1950s, and is used in the treatment of epilepsy. In cases of very severe epilepsy it is sometimes decided to perform brain surgery. The patient is operated on and ECoG electrodes are placed on the cortex. The ECoG measurements are then used to find the source of the seizure. Then this piece of cortex is surgically removed and patients are often seizure-free.
After an ECoG grid of electrodes has been placed, it may take several days before enough measurements have been made and the grid can be removed. During this time, the patient has nothing to do and scientists make use of this time by having the patient do all kinds of experiments. In this way, very valuable measurements can be collected, with superior temporal resolution (milliseconds) and reasonable spatial resolution (about 1 square centimetre).
Author: Michelle Moerel (translated by Thomas von Rein)