Friday Funda:

The EEG (electroencephalograph) measures brainwaves of different frequencies within the brain.

Electrodes are placed on specific sites on the scalp to detect and record the electrical impulses within the brain

Those are more analytic than BCI problems. More and more research in BCIs (and classification of EEG i general) is focused on getting models to work with raw, unprocessed data. In my opinion, way too little attention is paid to model evaluation and to final intended purpose. I think you should pay attention to when overfitting (and evaluation with n-fold crossvalidation) is beneficial (when creating a speller for a disabled person, for example meant to be used by that specific person and noone else) or detrimental (when a model is meant to be used by anyone in a plug-and-play fasion).