Modulating Cortical Dynamics of Dual-task Standing in MCI

Study Overview
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Brief Summary
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The investigators have designed a brain stimulation study to understand its effect on an individual's standing, walking, and thinking abilities in older adults with and without mild cognitive impairments (MCI). The transcranial alternating current stimulation (tACS) technology has been safely and effectively used in hundreds of individuals. The purpose of this study is to test whether a single session of tACS as compared to sham intervention, improves standing, walking, and thinking in older adults with and without mild cognitive impairments (MCI). Approximately 60 people will take part in this study.

Detailed Description
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Mild Cognitive Impairment (MCI) represents a common prodromal phase of dementia1. As compared to older adults who are cognitively-intact, those with MCI tend to exhibit poor dual-task standing balance performance; that is, the ability to maintain balance when standing and simultaneously performing an unrelated cognitive task. Moreover, those older adults who have worse dual-task standing balance are more likely to suffer falls and develop dementia. As such, strategies designed to understand and enhance the brain functionality involved in dual-task standing balance hold great promise to improve daily life function, and potentially, reduce the risk of dementia in this population. Surface electroencephalography (EEG) allows non-invasive assessment of brain activity dynamics over short periods of time, even when standing. It has been demonstrated in younger and older adults that dual-task standing is associated with brain activity fluctuations at specific frequencies. A recent study from our laboratory demonstrated that in older adults, 1) performance of a serial subtraction cognitive task when standing reduces fronto-central alpha power (i.e., fluctuations in the 8-13 Hz band), and 2) those with lower fronto-central alpha power when dual tasking exhibit worse dual task standing balance. Intriguingly, numerous studies have separately linked diminished alpha activity with worse performance on executive function and visuomotor tasks, as well as global cognitive decline in older adults. We therefore contend that therapeutic strategies designed to increase alpha activity hold promise to improve dual-task standing performance, and many other cognitive-motor functions in older adults with and without MCI. To date, however, the effects of enhancing fronto-central alpha activity to improve dual-task balance in older adults with and without MCI have not been studied. Transcranial alternating stimulation (tACS) is a safe, non-invasive brain stimulation technique that utilizes low-amplitude alternating currents to modulate brain activity and entrain specific cortical rhythms depending on the applied stimulation frequency. Targeting alpha band (10 Hz) in the frontal region has been shown to improve cognitive functioning in healthy older adults. However, no studies have investigated the effect of 10 Hz fronto-central stimulation on EEG alpha activity and postural sway outcomes during dual-task standing in older adults with and without MCI. We thus propose to conduct a within-subject cross-over, sham-controlled study in 30 older adults without an overt disease and 30 older adults with MCI. Participants will undergo dual-task standing and cognitive assessments immediately before and after single sessions of 10 Hz tACS (fronto-central alpha stimulation), and active-sham to understand the effect of different stimulation parameters on dual-task standing performance in older adults. We hypothesize that (1) older adults with MCI will demonstrate decreased EEG alpha power during dual-task standing compared to healthy controls, and decreased alpha power will be associated with worse balance outcomes during dual-task standing, and (2) compared to the pre-stimulation condition, participants will exhibit a greater increase in alpha power during the dual-task standing condition following tACS as compared to sham stimulation, and the increase in alpha power from pre-to-post tACS will correlate with a decrease in dual-task postural sway speed from pre-to-post tACS in older adults with and without MCI.

Official Title
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Understanding and Modulating Cortical Dynamics of Dual-task Standing in Older Adults With Mild Cognitive Impairment

Conditions
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Aging, Mild Cognitive Impairment

Intervention / Treatment
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* Other: real tACS
* Other: sham tACS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy older adults: Our target population will be healthy older men and women who are cognitively intact. We will also ensure that participants are not so impaired that they cannot safely participate nor potentially benefit from the intervention. Age 65+ without any cognitive impairment (based in MoCA or TICS) Willing and capable to give informed consent for the participation in the study after it has been thoroughly explained able and willing to comply with all study requirements informed consent form was signed Ability to stand and walk independently Understanding of the informed consent form (ICF) will be assessed by asking the participant to answer the following three questions: 1) What is the purpose of this study? 2) What are the risks of study involvement? 3) If you decide to participate, are you allowed to withdraw from the study at any time? Answers will be recorded by study personnel on the Assessment of Protocol Understanding form. Insufficient understanding will be defined by one or more incorrect answers, as determined at the discretion of the investigator. Older MCI participants: Age 65+ Who have been diagnosed with cognitive impairment (based in MoCA or TICS and Clinical Dementia Rating: CDR 0.5) Ability to stand and walk independently Willing and capable to give informed consent for the participation in the study after it has been thoroughly explained Cut off of MOCA score >18 will be applied Able and willing to comply with all study requirements informed consent form was signed Understanding of the ICF will be assessed by asking the participant to answer the following three questions: 1) What is the purpose of this study? 2) What are the risks of study involvement? 3) If you decide to participate, are you allowed to withdraw from the study at any time? Answers will be recorded by study personnel on the Assessment of Protocol Understanding form (see attached). Insufficient understanding will be defined by one or more incorrect answers, as determined at the discretion of the investigator. Exclusion Criteria: Healthy older adults: Exclusion Criteria have been selected to ensure safety and optimize compliance while minimizing confounds due to overt disease or conditions that may significantly influence study outcomes. Potentially eligible individuals will complete the Montreal Cognitive Assessment (MoCA) - score < 26 Major psychiatric co-morbidity including major depressive disorder, schizophrenia or psychosis Self-reported diagnosis of Parkinson's disease, Alzheimer's disease or dementia, multiple sclerosis, history of stroke or other neurodegenerative disorder. Self-reported active cancer for which chemo-/radiation therapy is being received. Blindness or other disabilities that prevent task performance Contraindications to tACS, as recorded on a standardized screening questionnaire, which include a reported seizure within the past two years, use of neuroactive drugs, self-reported presence of specific implanted medical devices (e.g., deep brain stimulator, medication infusion pump, cochlear implant, pacemaker, etc.), or the presence of any active dermatological condition, such as eczema, on the scalp Inability to stand or ambulate unassisted for at least 25 feet Hospitalization within the past 3 months due to acute illness or as a result of musculoskeletal injury significantly affecting gait and balance Older MCI participants: Cut off of MOCA score <18 will be applied Major psychiatric co-morbidity including major depressive disorder, schizophrenia or psychosis Blindness or other disabilities that prevent task performance Self-reported history of stroke or neurodegenerative disorders other than MCI. Self-reported active cancer for which chemo-/radiation therapy is being received. Contraindications to tACS, as recorded on a standardized screening questionnaire, which include a reported seizure within the past two years, use of neuro-active drugs, self-reported presence of specific implanted medical devices (e.g., deep brain stimulator, medication infusion pump, cochlear implant, pacemaker, etc.), or the presence of any active dermatological condition, such as eczema, on the scalp.

Ages Eligible for Study
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Minimum Age: 65 Years
Maximum Age: 95 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: real tACS<br>The investigators will administer the transcranial alternating current stimulation (tACS) intervention at 10 Hz to the participants. This intervention will utilize 6 electrodes; electrode placement and current parameters for each electrode have been optimized using a standard brain to generate an average electric field of 0.25 V/m. To ensure adherence to current safety recommendations for tACS, optimizations will be constrained to a maximum of total injected current 4.0 mA and a max. current per electrode of 2.0 mA. Stimulation will start and end with a 60 s ramp up/down to maximize comfort. This standard approach is both well-tolerated and safe in older adults. In a separate visit, we will use an active sham in which very low-level currents (0.5 mA total) will be transferred between electrodes in close proximity on the scalp throughout the entire 20-minute session. | Other: real tACS<br>* The participant will receive one session of 10 Hz tACS for 20-minutes<br>|
| Sham Comparator: sham tACS<br>The investigators will administer the sham tACS intervention to the participants. They will use an active sham in which very low-level alternating currents (0.5 mA total) will be transferred between electrodes in close proximity on the scalp throughout the entire 20-minute session. | Other: sham tACS<br>* The participant will receive one session of active-sham tACS for 20-minutes<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EEG alpha-band power | EEG oscillations and frequency coupling at 8-13 Hz | Change from immediately before and after each 20-minute session of tACS | 
| Postural sway speed | This metric assesses the ability to control standing posture | Change from immediately before and after each 20-minute session of tACS | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Timed Up and Go Test (TUG) | A common field test of mobility | This outcome will be assessed immediately before and after each 20-minute session of tACS | 
| Postural sway area | This metric assesses the ability to control standing posture | This outcome will be assessed immediately before and after each 20-minute session of tACS | 
| Postural sway path | This metric assesses the ability to control standing posture | This outcome will be assessed immediately before and after each 20-minute session of tACS | 
| EEG theta-band power | EEG oscillations and frequency coupling at 4-7 Hz | This outcome will be assessed immediately before and after each 20-minute session of tACS | 
| EEG beta-band power | EEG oscillations and frequency coupling at 13-30 Hz | This outcome will be assessed immediately before and after each 20-minute session of tACS | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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aging, mild cognitive impairment, non-invasive brain stimulation