The aim of the MicroEPI study is to know whether it is possible to use safely a medical device (a micro-electrode) that allows recording the activity of neurons in the human brain. Patients who suffer from drug-resistant epilepsy and who are candidates to epilepsy surgery to alleviate their condition sometimes require the implantation of intracranial EEG electrodes for a few weeks, in order to determine as best as possible which region of the brain to operate on. In the MicroEPI study, some of these electrodes will also comprise micro-electrodes, allowing us to record the activity of the patients' neurons during their epileptic seizures.