Patient description: The patient is a 55-year-old man who was recently diagnosed with Parkinson's disease. He is complaining of slowness of movement and tremors. His disease is ranked as mild, Hoehn-Yahr Stage I. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with gardening before his diagnosis. He complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is offered Levodopa and Trihexyphenidyl. He is an alert and cooperative man who does not have any signs of dementia. He does not smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Parkinson Disease Any Subject Male or female, age: >18 years Capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form Sufficiently fluent in English that they are able to understand written and spoken instructions in the opinion of the investigator  Subjects with previous or current drug or alcohol dependence within 2 years of screening Subjects who are unable to tolerate study procedures including MRI, or who are unable to perform the study procedures (e.g. due to severe musculoskeletal disease) Use of other prescription or non-prescription centrally acting drugs, including herbal (eg khat) and dietary supplements within 7 days or 5 half-lives (whichever is longer) prior to the procedures of Day 1, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety Pregnant females as determined by positive serum or urine hCG test at screening Lactating females Unwillingness or inability to follow the procedures outlined in the protocol Subject is mentally or legally incapacitated Subject meets any of the MRI Subject is left-handed. PKD Patients Diagnosis of Parkinson's disease according to the following derived from the UKPD Society brain bank diagnostic for PD (Hughes AJ et al., 1992): a) Bradykinesia must be present b) At least one of the following: muscular rigidity Resting tremor postural instability not caused by primary visual, vestibular, cerebellar or proprioceptive dysfunction c) Supportive prospective positive for Parkinson's Disease (three of the following required for definite diagnosis): Resting tremor unilateral onset progressive disorder in first 5 years following onset, persistent asymmetry affecting side on which symptoms first appeared excellent response (70-100%) to levodopa in the clinical judgement of the investigator, based on the medical notes or during standard care d) None of the following clinical features which suggest a diagnosis other than Parkinson's disease: History of repeated strokes with stepwise symptom progression History of repeated head injury History of definite encephalitis Neuroleptic treatment at symptom onset Sustained remission Strictly unilateral features after 3 years Supranuclear gaze palsy Cerebellar signs In first five years following onset, early severe autonomic involvement such as orthostatic hypotension, impotence and bladder dysfunction Early (within 2 years on symptom onset) severe dementia with disturbed memory, language, praxis Babinski sign CT/MRI scan evidence of tumour or hydrocephalus Negative response to 1000mg of levodopa daily in divided doses. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposure