This clinical trial has been designed to study and compare changes in deep brain activity (field potentials) in Parkinson's disease (PD) patients while awake, and during sedation with dexmedetomidine or propofol. The recording is made through a deep brain stimulation (DBS) electrode implanted for PD management.

The investigators hypothesize that dexmedetomidine produces fewer changes as compared to propofol, and that those changes are consistent and recognizable when compared to activity in patients not exposed to any sedation. Typification of those changes would in the future allow for patients to undergo this surgery comfortably while not compromising the quality of the recording and of the final clinical outcome. The principal variable analyzed is the signal's power in each of the frequency bands, absolute and relative. The analysis will include usual clinical methods such as rapid Fourier transform (FFT) and window fast Fourier transform (WFFT), wavelet analysis, Gabor, and coherence.

Comparative clinical trial, non blinded, controlled and sequential, evaluating the effects of propofol and dexmedetomidine in the basal ganglia of PD patients through a DBS electrode.

It is a phase IV clinical trial evaluating the effects of a drug outside the approved.

The study takes part in three phases:

1. DBS placement under sedation with dexmedetomidine at 0.2 μg/kg/h. This will be called "dexmedetomidine record".
2. Four days later and with no sedation, a recording will be registered in one of the specialized electrically isolated rooms at the Neurophysiology Department. This will be dubbed "basal recording". The equipment used is also the standard one used for routine postoperative recordings.
3. 5 days after the initial surgery, and following the protocol in place for these procedures, the tunnelization and battery placement will take place. This is done under general anaesthesia. During anaesthetic induction, the patient is exposed to incremental doses of propofol. Different plasmatic concentrations will be targeted using the mathematical model in the target controlled infusion (TCI) pump. These recordings will be called "propofol at a 0.5, 1, 1.5, 2, 2.5 μg/mL".

Inclusion Criteria:

• Capacity to understand, consent and commit for the three phases of the study.
• Older than 18 years old.
• The patient is scheduled for DBS electrode placement for PD treatment by his neurologist.

Exclusion Criteria:

• Allergy or hypersensibility to dexmedetomidine or propofol
• Cardiac blockade (types 2 and 3) without an implanted pacemaker
• Low blood pressure (mean < 60 mmHg) or symptoms of low cardiac output.
• Severe cerebrovascular disease.
• Pregnancy or nursing mothers.