Measuring synchronization: An overview of the most frequently used methods

Abstract

From the moment gamma-band synchronization has been proposed to be a mechanism for the integration of neuronal populations in functional areas widely distributed over the brain, there has been a need for a reliable and robust method to measure this synchronization. This method could then be applied to noninvasive measurements, performed by MEG or EEG, on the human brain in order to study synchronization between di erent brain areas. In the past two decades several types of measures have been introduced and have been applied mainly to EEG and MEG studies on subjects performing simple tasks during the measurement and epileptic patients, with results giving an insight into some of the neuronal processes going on in the brain. Despite the interesting results, often spurious synchronizations is measured, the result is spoiled by the large amount of noise present or measures are applied to noncorresponding situations, such as stationary measures being applied in nonstationary situations. An overview of the most often used measures to detect synchronization is presented and commented here.