Defining Phenotypes of Movement Disorders :Parkinson's Plus Disorders (PD), Essential Tremor (ET), Cortical Basal Degeneration (CBD), Multiple Systems Atrophy (MSA), Magnetoencephalography.

Specific Aim 1: Determine which features of resting Magnetoencephalography (MEG) brain
activity most sensitively discriminate between PD with normal cognition, PD with mild
cognitive impairment (MCI), and PD dementia (PDD). Investigators predict that frontal network
slowing and connectivity will discriminate between normal cognition and MCI while
visuospatial network involvement will distinguish the PDD group.

Specific Aim 2: Determine which features of resting MEG brain activity most sensitively
discriminate PDD from Alzheimer's Disease. Investigators predict that PDD will be
distinguished from Alzheimer's (AD) on the basis of increased network connectivity,
particularly in frontal and visuospatial networks.

Specific Aim 3 Investigate how resting state MEG activity correlates with task related brain
activity. Investigators predict that resting state slowing will be associated with decreased
task related brain activity.

Specific Aim 4: Determine which features of resting MEG brain activity most sensitively
discriminate between motor subtypes of PD and also other relevant clinical populations
(essential tremor and Parkinson plus syndromes). Investigators predict that frontal and
parietal slowing and connectivity will discriminate PD from related conditions and that
patterns of motor cortex connectivity and activity will differentiate among PD motor
phenotypes.

Inclusion Criteria:

- All subjects will be age 40 or older,

- Be on stable medications for at least 30 days

- Montreal Cognitive Assessment (MOCA) of 26 or higher

- Scores within 1.5 standard deviations of age-matched norms for all neuropsychological
tests

- Parkinson's Plus Disorders (PD) will be defined using United Kingdom (UK) Brain Bank
Criteria.

- PD dementia (PDD) will be defined using the Movement Disorder Task Force 2007 criteria
and supported by scores less than 1.5 standard deviations of age-matched norms in at
least two domains.

- Probable Alzheimer's Disease (AD) will be defined using the National Institute on
Aging-Alzheimer Association 2011 guidelines.

- Parkinson's Plus Disorders (PD) with mild cognitive impairment (MCI) will be defined
by history, MOCA of 21 or higher, at least one score less than 1.5 standard deviations
of age-matched norms, and cannot meet diagnostic criteria for PDD.

- Essential tremor and Parkinson plus syndromes (multiple systems atrophy, corticobasal
degeneration, progressive supranuclear palsy) will be defined using previously
published research criteria.19-22

Exclusion Criteria

- Features suggestive of other causes of parkinsonism/Parkinson-plus syndromes;

- Features suggestive of other causes of dementia, including moderate to severe
cerebrovascular disease by history, or imaging or history of major head trauma;

- History of deep brain stimulation, ablation surgery, or other brain surgery;

- Evidence for depression based on the Hospital Anxiety Depression Scale (score > 11).