Kellyann Geurts and many of the scientists in the studies I researched use non-invasive electroencephalograph or EEG’s to measure brain activity. Electroencephalograms (EEGs) monitor activity through electrical currents picked up from the brain through the scalp. Small electrodes are placed on the scalp and detect changes in electrical current in the brain, the EEG amplifies these currents and records them in a wave pattern on a computer or on paper using a needle. Its high level of accuracy is relatively recent however. In the 80 years it has existed much of that time the data collected using it was discredited through other means of neuroimaging. These inaccuracies were not due to the device but instead to the readings of the data. As we now know more about the constant electrical current of neural activity in the brain and measurement of electrical signals on the scalp, EEG readings are much more accurate and paint a much clearer picture of the brain in thought. EEG’s are straightforward to operate and are therefore widely used in the scientific (and artistic, in the case of Kellyann Geurts) field.
Source: Dr Tim Kenny, Dr Colin Tidy, Prof Cathy Jackson. “Electroencephalograph (EEG).” 23 December 2015. Web. 17 January 2016.