The purpose of this study is to better understand why individuals with Progressive Supranuclear Palsy (PSP) fall. Understanding the mechanism of gait and balance dysfunction in individuals with PSP may provide us with important early diagnostic tools, allowing for earlier identification of mobility problems and to better evaluate medical therapies aimed at improving motor disability.

The investigators will recruit 10 PSP, 10 PD and 10 healthy controls for the study. All subjects will be asked to come to the OHSU clinic at the Center for Health and Healing for an initial screening visit. They will meet with the primary investigator to conduct a brief interview and physical examination. In addition, they will be asked to answer questions regarding current and past medical illness, how often they fall and what kinds of medications they are on.

Subjects who agree to participate will come to the Oregon Clinical and Translational Research Institute (OCTRI) at OHSU for balance testing. Subjects will be asked to stand or sit on a movable platform with eyes open or closed. Prior to standing on the platform, the investigators will place 6 small sensors on body which are held in place by velcro straps (one on each wrist, ankles, chest and lower back). The platform will then be moved (tilt or slide) while subjects try to keep their balance. During all of the balance tests described above, body movements will be recorded from the sensors on the subjects' body. This data is directly recorded by a computer and analyzed to help us gain better understanding of the subjects' posture and their ability to remain up right.

Inclusion Criteria:

1. Diagnosis of probable or possible PSP as defined by the National Institute of Neurological Disorders and Stroke and Society for Progressive Supranuclear Palsy (NINDS-SPSP) diagnostic criteria.
2. Be able to ambulate and stand unassisted for 5 minutes
3. Be able to cooperate with gait and balance testing
4. Be able to give informed consent.

Exclusion Criteria:

1. Cannot exhibit behavior or have dementia that precludes participation in the protocol
2. Cannot have medical or orthopedic illness that, in the investigator's opinion, would impact the patient's postural control or ability to participate in the study.

OHSU Movement Disorders Clinic Volunteers from the community (Portland, Oregon and surrounding areas)