By analyzing the SEEG recordings, we explore the range of cortical functional responses to strings of 77.5Hz stimulations delivered by tACS,

Inclusion Criteria:

• All epileptic patients that would receive the implantation of SEEG electrodes, regardless of the seizure locations;
• There was no metal implantation before;
• Eligible for MRI examination;
• No other lesional neurological disorders;
• Could be well informed by the study protocols.

Exclusion Criteria:

• Suffered from any other mental illnesses prior to the enrollment;
• Those suffering from the serious or unstable organic diseases;
• Pregnant or lactation women, and those who have a plan of pregnant;
• Patients with central nervous system tumors, acute brain injury or infection;
• Skin injured, or allergic to the exposure of the conductive gel;
• Those with implanted devices;
• Those who received modified electrical convulsive therapy, or TMS within the recent one month;
• The score of item 3 (suicidal item) in HAMD-17 equal or greater than 3;
• Enrolled in any other on going trials;
• Other situations evaluated by the researchers as inappropriate to the enrollment