Cerebellar Transcranial Direct Current Stimulation in Parkinson's Disease
Cerebellar Transcranial Direct Current Stimulation in Parkinson's Disease
Parkinson's disease (PD) is the second most common neurodegenerative disorder and affects
 approximately 1 million people in the United States with total annual costs approaching 11
 billion dollars. The most common symptoms of PD are tremor, stiffness, slowness, and trouble
 with balance/walking, which lead to severe impairments in performing activities of daily
 living. Current medical and surgical treatments for PD are either only mildly effective,
 expensive, or associated with a variety of side-effects. Therefore, the development of
 practical and effective add-ons to current therapeutic treatment approaches would have many
 benefits. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation
 technique that can affect brain activity and can help make long-term brain changes to improve
 functions like walking and balance. While a few initial research studies and review articles
 involving tDCS have concluded that tDCS may improve PD walking and balance, many results are
 not meaningful in real life and several crucial issues still prevent tDCS from being a useful
 add-on intervention in PD. These include the selection of stimulation sites (brain regions
 stimulated) and tDCS electrode placement. Most studies have targeted the motor cortex (brain
 region that controls intentional movement), but there is evidence that the cerebellum - which
 helps control gait and balance, is connected to several other brain areas, and is easily
 stimulated with tDCS - may be a likely location to further optimize walking and balance in
 PD. There is also evidence that certain electrodes placements may be better than others.
 Thus, the purpose of this study is to determine the effects of cerebellar tDCS stimulation
 using two different placement strategies on walking and balance in PD.

 Additionally, although many tDCS devices are capable of a range of stimulation intensities
 (for example, 0 mA - 5 mA), the intensities currently used in most tDCS research are less
 than 2 mA, which is sufficient to produce measurable improvements; but, these improvements
 may be expanded at higher intensities. In the beginning, when the safety of tDCS was still
 being established for human subjects, careful and moderate stimulation approaches were
 warranted. However, recent work using stimulation at higher intensities (for example, up to 4
 mA) have been performed in different people and were found to have no additional negative
 side-effects. Now that the safety of tDCS at higher intensities is better established,
 studies exploring the differences in performance between moderate (i.e., 2 mA) and higher
 (i.e., 4 mA) intensities are necessary to determine if increasing the intensity increases the
 effectiveness of the desired outcome.

 Prospective participants will include 10 people with mild-moderate PD that will be recruited
 to complete five randomly-ordered stimulation sessions, separated by at least 5 days each.
 Each session will involve one visit to the Integrative Neurophysiology Laboratory (INPL) and
 will last for approximately one hour. Data collection is expected to take 4-6 months. Each
 session will include walking and balance testing performed while wearing the tDCS device.
 Total tDCS stimulation time for each session will be 25 minutes.
Parkinson's disease (PD) is the second most common neurodegenerative disorder and affects
 approximately 1 million people in the United States with total annual costs approaching 11
 billion dollars. The most common symptoms of PD are tremor, stiffness, slowness, and trouble
 with balance/walking, which lead to severe impairments in performing activities of daily
 living. Current medical and surgical treatments for PD are either only mildly effective,
 expensive, or associated with a variety of side-effects. Therefore, the development of
 practical and effective add-ons to current therapeutic treatment approaches would have many
 benefits. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation
 technique that can affect brain activity and can help make long-term brain changes to improve
 functions like walking and balance. While a few initial research studies and review articles
 involving tDCS have concluded that tDCS may improve PD walking and balance, many results are
 not meaningful in real life and several crucial issues still prevent tDCS from being a useful
 add-on intervention in PD. These include the selection of stimulation sites (brain regions
 stimulated) and tDCS electrode placement. Most studies have targeted the motor cortex (brain
 region that controls intentional movement), but there is evidence that the cerebellum - which
 helps control gait and balance, is connected to several other brain areas, and is easily
 stimulated with tDCS - may be a likely location to further optimize walking and balance in
 PD. There is also evidence that certain electrodes placements may be better than others.
 Thus, the purpose of this study is to determine the effects of cerebellar tDCS stimulation
 using two different placement strategies on walking and balance in PD.

 Additionally, although many tDCS devices are capable of a range of stimulation intensities
 (for example, 0 mA - 5 mA), the intensities currently used in most tDCS research are less
 than 2 mA, which is sufficient to produce measurable improvements; but, these improvements
 may be expanded at higher intensities. In the beginning, when the safety of tDCS was still
 being established for human subjects, careful and moderate stimulation approaches were
 warranted. However, recent work using stimulation at higher intensities (for example, up to 4
 mA) have been performed in different people and were found to have no additional negative
 side-effects. Now that the safety of tDCS at higher intensities is better established,
 studies exploring the differences in performance between moderate (i.e., 2 mA) and higher
 (i.e., 4 mA) intensities are necessary to determine if increasing the intensity increases the
 effectiveness of the desired outcome.

 Prospective participants will include 10 people with mild-moderate PD that will be recruited
 to complete five randomly-ordered stimulation sessions (baseline/SHAM, unilateral tDCS
 montage at 2 mA, unilateral tDCS montage at 4 mA, bilateral tDCS montage at 2 mA, and
 bilateral montage at 4 mA), separated by at least 5 days. Each session will involve one visit
 to the Integrative Neurophysiology Laboratory (INPL) and will last for approximately one
 hour. Data collection is expected to take 4-6 months. Each session will include gait
 (30-meter walk test [30mWT], 6-minute walk test [6MWT], Timed Up and Go [TUG]) and balance
 testing (standing on a force platform with either a firm surface or a foam surface) performed
 in conjunction with one of the five randomly-ordered stimulation conditions (SHAM, unilateral
 2 mA, unilateral 4 mA, bilateral 2 mA, and bilateral 4 mA). Total tDCS stimulation time for
 each session will be 25 minutes. Gait characteristics (i.e., gait speed, stride length, step
 length, toe-off angle, etc.) and distance walked during the 30mWT and 6MWT will also be
 determined with inertial sensors (OPAL motion sensors).
Inclusion Criteria:

 -  1) Adult (50-90 yrs) with a positive diagnosis of Parkinson's disease from a movement
 disorder specialist

 -  2) an unchanged regimen of dopaminergic medication for at least the last 3 months

 -  3) able to independently walk for 6 min

 -  4) without other chronic psychiatric or medical conditions

 -  5) not taking any psychoactive medications

 Exclusion Criteria:

 -  1) pregnant

 -  2) known holes or fissures in the skull

 -  3) metallic objects or implanted devices in the skull (e.g., metal plate, deep brain
 stimulator)

 -  4) current or previous injuries or surgeries that cause unusual gait

 -  5) score less than 24 or 17 on the Montreal Cognitive Assessment or telephone-Montreal
 Cognitive Assessment, respectively

 -  6) experience freezing of gait

 -  7) a diagnosis of dementia or other neurodegenerative diseases