An electro-encephalography system includes an internal device (102) for implantation below a scalp and above a skull of a patient, and an external device (104) to be worn or carried outside the patient1 s body. The internal device includes a first electrode (124) for receiving neurological signals originating from the patients brain and a second electrode (124) for receiving artifacts originating from sources other than the patients brain. The external device (104) includes a processing unit for receiving data from the internal device, mitigating the effects of the artifacts, and determining a neurological state of the patient. A therapy device is included to provide a therapy to the patient based on the patients neurological state.
