The purpose of this study is to provide proof-of-concept that directional stimulation, in an intraoperative setting, is perceivable in a subject and is different from omnidirectional stimulation. The tests will be performed using a dedicated DBS lead connected to external neurostimulator.

Inclusion Criteria:

• Subject is indicated to undergo DBS for Parkinson's disease or Essential Tremor according to criteria of the Study site

• For Parkinson Disease:

  • Person is between 18 and 75 years of age
  • Established diagnosis of idiopathic Parkinson's disease with progression of symptoms for a minimum of 2 years.
  • Person has a history of at least 30% improvement on the Unified Parkinson's Disease Rating Scale with therapy in L-dopa (levodopa)
  • Weak control of symptoms by dopaminergic therapy (off phenomenon, fluctuations on / off, dyskinesia on)

• For Essential Tremor:

  • Person is between 18 and 80 years of age
  • Established diagnosis of Essential Tremor for a minimum of 2 years
  • Functional disability due to tremor was not adequately controlled by medication for at least 3 months prior to implant.

• Person has given his/her written consent

Exclusion Criteria:

• Person suffering from an active major psychiatric disorder
• Mattis Dementia Rating Scale score <130 or otherwise not capable of discernment
• Presence of major co-morbidity or medical condition that may affect participation to the study
• Presence of an electrical or electromagnetic implant (e.g., cochlear implant, pacemaker)
• Person with a previous surgery for the treatment of Parkinson's disease or Essential Tremor
• Person with a previous brain ablation procedure
• Person who suffers from epilepsy
• Person who is pregnant: a pregnancy test will be performed in women of childbearing age
• Person with coagulopathies
• Abuse of drugs or alcohol