Glossokinetic-artifact (GKA) is a long known scalp-EEG artifact. It is seen as a broad potential field maximum in the frontal electrodes and produces synchronous intermittent rhythmic activity in the range of slow delta to low theta. It is commonly attributed to the difference in electrical polarity between the base and the tip of the tongue, i.e. tongue as an inherent dipole. To our knowledge, this is the first study showing intracranial-EEG changes in relation to scalp GKA.

We assessed simultaneous scalp and intracranial-EEG recordings of five consecutive patients who exhibited GKA on scalp-EEG. The patients underwent invasive-EEG evaluations at Yale in 2017-2018 for the localization of their drug-resistant focal epilepsies. EEG was sampled at 2000-4000 Hz and analyzed with a monopolar montage employing standard review and quantitative settings. An active ground reference system was employed based on two inverted electrodes placed either in the diploic space or over the frontoparietal regions. We analyzed 10 GKA deflections per patient. 

The common view of the tongue as a dipole-generator of GKA is simplistic and does not account for the findings reported herein. Other considerations include shunting of scalp currents via the tongue or other scalp and soft-tissue near-field potentials. Knowledge of tongue potentials is of interest in education and in tongue-computer-interfaces.