Advances in Electrode Materials for Scalp, Forehead, and Ear EEG: A Mini-Review

Electroencephalogram (EEG) records the electrical activityof neurons in the cerebral cortex and is used extensively to diagnose,treat, and monitor psychiatric and neurological conditions. Reliablecontact between the skin and the electrodes is essential for achievingconsistency and for obtaining electroencephalographic information.There has been an increasing demand for effective equipment and electrodesto overcome the time-consuming and cumbersome application of traditionalsystems. Recently, ear-centered EEG has met with growing interestsince it can provide good signal quality due to the proximity of theear to the brain. In addition, it can facilitate mobile and unobtrusiveusage due to its smaller size and ease of use, since it can be usedwithout interfering with the patient's daily activities. Thepurpose of this mini-review is to first introduce the broad rangeof electrodes used in conventional (scalp) EEG and subsequently discussthe state-of-the-art literature about around- and in-the-ear EEG.