Cerebral Networks of Locomotor Learning and Retention in Older Adults
Phase: PHASE1
Conditions: Aging
Sponsor: VA Office of Research and Development

Protocol #:  IRB201803010 
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 Protocol 
1. Project Title
Cerebral networks of locomotor learning and retention in older adults
2. Investigator(s):
David J. Clark, ScD 
Dorian Rose, PhD 
William Triggs, MD 
3. Abstract:
Aging often leads to substantial declines in walking function, especially for walking tasks that 
are more complex such as obstacle crossing. This is due in part to a lack of continued practice 
of complex walking (sedentary lifestyle) combined with age-related deficits of brain structure and 
the integrity of brain networks. Neurorehabilitation can contribute to recovery of lost walking 
function in older adults, but major and persistent improvements are elusive. A cornerstone of 
neurorehabilitation is motor learning, defined as an enduring change in the ability to perform a 
motor task due to practice or experience. Unfortunately, in most clinical settings, the time and 
cost demands of delivering a sufficiently intensive motor learning intervention is not feasible. 
There is a need for research to develop strategies for enhancing motor learning of walking 
(“locomotor learning”) in order to improve the effectiveness of neurorehabilitation. 
The objective of this study is to use non-invasive brain stimulation to augment locomotor 
learning and to investigate brain networks that are responsible for locomotor learning in older 
adults. We have shown that frontal brain regions, particularly prefrontal cortex, are crucial to 
control of complex walking tasks. Our neuroimaging and neuromodulation studies also show 
that prefrontal cortex structure and network connectivity are important for acquisition and 
consolidation of new motor skills. However, a major gap exists regarding learning of walking 
tasks. This study is designed to address this gap. Our pilot data from older adults shows that 
prefrontal transcranial direct current stimulation (tDCS) administered during learning of a 
complex obstacle walking task contributes to multi-day retention of task performance. In this 
study we will build upon this pilot work by conducting a full scale trial that also investigates 
mechanisms related to brain structure, functional activity, and network connectivity. We will 
address the following specific aims: 
Specific Aim 1: Determine the extent to which prefrontal tDCS augments the effect of task 
practice for retention of performance on a complex obstacle walking task. 
Specific Aim 2: Determine the extent to which retention of performance is associated with 
individual differences in baseline and practice-induced changes in brain measures (working 
memory, gray matter volume, task-based prefrontal activity, and brain network segregation). 
Specific Aim 3: Investigate the extent to which tDCS modifies resting state network segregation. 
We anticipate that prefrontal tDCS will augment retention of locomotor learning, and that our 
data will provide the first evidence of specific brain mechanisms responsible for locomotor 
learning/retention in older adults. This new knowledge will provide a clinically feasible 
intervention approach as well as reveal mechanistic targets for future interventions to 
enhance locomotor learning and rehabilitation. 
4. Background:
1&7

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Aging often leads to substantial declines in walking function, especially for walking tasks that 
are more complex such as obstacle crossing. This is due in part to a lack of continued practice 
of complex walking (sedentary lifestyle) combined with age-related deficits of brain structure and 
the integrity of brain networks. Neurorehabilitation can contribute to recovery of lost walking 
function in older adults, but major and persistent improvements are elusive. A cornerstone of 
neurorehabilitation is motor learning, defined as an enduring change in the ability to perform a 
motor task due to practice or experience. Unfortunately, in most clinical settings, the time and 
cost demands of delivering a sufficiently intensive motor learning intervention is not feasible. 
There is a need for research to develop strategies for enhancing motor learning of walking 
(“locomotor learning”) in order to improve the effectiveness of neurorehabilitation. 
 
The objective of this study is to use non-invasive brain stimulation to augment locomotor 
learning and to investigate brain networks that are responsible for locomotor learning in older 
adult Veterans. We have shown that frontal brain regions, particularly prefrontal cortex, are 
crucial to control of complex walking tasks. Our neuroimaging and neuromodulation studies also 
show that prefrontal cortex structure and network connectivity are important for acquisition and 
consolidation of new motor skills. For instance, our published data shows that resting state 
connectivity of prefrontal networks predicts sensorimotor task performance and learning. 
Furthermore, prefrontal tDCS enhances multi-day retention of performance on a complex dart 
throwing task. However, a major gap exists regarding learning of locomotor (walking) tasks. This 
study is designed to address this gap. Our pilot data show that bihemispheric prefrontal tDCS 
administered during a single session of learning on a complex obstacle walking task contributes 
to multi-day retention of task performance. In this study we will build upon this pilot work by 
conducting a full-scale trial that also investigates mechanisms related to brain structure, 
functional activity, and network connectivity. 
 
5. Specific Aims: 
 
Specific Aim 1: Determine the extent to which prefrontal tDCS augments the effect of 
task practice for retention of performance on a complex obstacle walking task. 
Hypothesis 1: Retention on the obstacle walking task at 1-week (primary outcome) and 1-month 
post-training will be significantly higher for an active prefrontal tDCS group versus a sham tDCS 
group. 
 
Specific Aim 2: Determine the extent to which retention of performance is associated 
with individual differences in baseline and practice-induced changes in brain measures. 
Hypothesis 2a: Better retention on the obstacle walking task will be associated with baseline 
greater working memory performance, greater prefrontal gray matter volume, and greater task-
based prefrontal fNIRS activity. 
Hypothesis 2b: Better retention on the obstacle walking task will be associated with training-
induced increased prefrontal gray matter volume and reduction of task-based prefrontal fNIRS 
activity (indicating neural efficiency and/or reduced executive demands). 
Hypothesis 2c: Better retention on the obstacle walking task will be associated with baseline 
network connectivity, including resting default mode network segregation. 
 
Specific Aim 3: Investigate the extent to which tDCS modifies resting state network 
segregation. 
Hypothesis 3: Compared to the sham tDCS group, the active tDCS group will demonstrate 
improved segregation of resting state networks at post-training relative to baseline. 
 
6. Research Plan: 
 

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Study Overview
Up to one hundred older men and women will be enrolled in the intervention component of this 
study.  An additional 15 participants (estimated) may enroll in the intervention but discontinue 
participation before completing the protocol. A larger number (up to 400) may participate in 
screening by telephone and/or onsite, but will fail the screening tests and not proceed to the 
study intervention. Participants will undergo the following sequence of events:
x
Telephone Screening: Participants will be screened by telephone to determine if they 
meet basic enrollment criteria including age and general health status. If patients 
authorized us to view their medical records, those records may be examined to verify 
absence of exclusion diagnoses, to obtain complete/accurate medication lists, and to 
assess whether participants have successfully completed prior MRI scans.
x
Informed Consent and Onsite Screening Visit: 
Participants who pass the phone screen will 
be invited to participate in on-site screening.  
Informed consent will be obtained.  Mobility 
function, cognitive function, and health/safety
screening will be conducted. This single visit 
will last approximately 3.5 hours. Qualifying 
participants will be invited to participate in the 
full study with or without MRI.
x
Baseline Participants will undergo a test of 
walking over obstacles, turning while walking 
(90 degree turns and 180 degree turns), 
turning while standing in place (360 degree 
turn), cognitive function, blood draw, and MRI 
scans at the UF McKnight Brain Institute 
(structural, functional, and resting state MRI 
scans) if MRI screening passed. Baseline 
assessment will last about 4 hours and may be 
completed over 1 or 2 visits based on 
scheduling flexibility of the participant, study 
personnel, and equipment.
x
Study Intervention Visits: Participants will 
attend four intervention sessions in which they 
will practice a “locomotor learning” task 
comprised of a 10m walking course with 
obstacles and transitions between hard and 
soft floor surfaces. During this task they will receive either active or sham transcranial 
The obstacles walking task includes 
a series of foam obstacles and foam 
mats. This walking task is used for 
baseline visits, study intervention
visits, and post visits.

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direct current stimulation (tDCS) to the frontal portion of the brain. Each visit will last 
approximately one hour. 
x 
1-Day Post Assessment: Participants will undergo a test of walking over obstacles. 
x 
1-Week Post Assessment: Participants will undergo a test of walking over obstacles, 
cognitive function assessment, blood draw, and MRI scans (MRI eligible participants 
only) at the UF McKnight Brain Institute (structural, functional, and resting state MRI 
scans). Post assessments will last about 4 hours and may be completed over 1 or 2 
visits based on scheduling flexibility of the participant, study personnel, and equipment. 
x 
Visit 9: 1-Month Post Assessment: Participants will undergo a test of walking over 
obstacles, turning tasks, and cognitive function assessment. This visit will last 
approximately 2 hours. 
_____________________________________________________________________________________ 
Telephone Screening 
Participants will be screened by telephone to determine if they meet the following criteria: 
Inclusion criteria 
x 
Age 65 - 95 years 
x 
Willingness to be randomized to either intervention and to participate in all aspects of 
study assessment and intervention 
 
Exclusion criteria 
x 
Diagnosed neurological disorder or injury of the central nervous system, or observation 
of symptoms consistent with such a condition (spinal cord injury, Alzheimer’s, 
Parkinson’s, stroke, etc.) 
x 
Contraindications to non-invasive brain stimulation (e.g., metal in head, wound on scalp) 
x 
Contraindications to MRI (claustrophobia, metal anywhere in body, etc.). 
x 
Use of medications affecting the central nervous system including, but not limited to, 
benzodiazepines, anti-cholinergic medication and GABAergic medication. 
x 
severe arthritis, such as awaiting joint replacement 
x 
current cardiovascular, lung or renal disease; diabetes; terminal illness 
x 
myocardial infarction or major heart surgery in the previous year 
x 
cancer treatment in the past year, except for nonmelanoma skin cancers and cancers 
having an excellent prognosis (e.g., early stage breast or prostate cancer) 
x 
current diagnosis of schizophrenia, other psychotic disorders, or bipolar disorder 
x 
difficulty communicating with study personnel (including people who cannot speak 
English) 
x 
uncontrolled hypertension at rest (systolic > 180 mmHg and/or diastolic > 100 mmHg) 
x 
bone fracture or joint replacement in the previous six months 
x 
current participation in physical therapy for lower extremity function or cardiopulmonary 
rehabilitation 
x 
current enrollment in any clinical trial 
x 
clinical judgment of investigative team 
______________________________________________________________________ 
Informed Consent and Onsite Screening Visit 
 
Upon arriving to the research site, participants will undergo informed consent.  We will explain 
the full study protocol including transcranial direct current stimulation and MRI. 

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All questions from the phone screening will be repeated, and additional health/medical 
screening criteria will be evaluated. This will include: 
x 
Resting blood pressure   
x 
Basic visual examination with Snellen eye chart 
x 
Height, weight, age, sex, education level, socioeconomic status 
x 
Medical history 
x 
Obtain list of medications that the participant is currently using 
x 
Various walking tasks including typical walking, fast walking, walking over obstacles, 
walking while carrying a tray, and combinations of these tasks. 
x 
Somatosensory assessments of the foot based on tactile pressure sensation. 
x 
Activities Specific Balance Confidence Scale: 16-item questionnaire that gauges 
confidence (on a scale of 0-100%) on various balance and walking tasks relevant to 
household and community ambulation. 
x 
Berg Balance Scale: 14-item assessment of balance task performance to assess 
balance ability and fall risk. 
x 
Movement-specific Reinvestment Scale: questionnaire that asked about the extent to 
which a person directs conscious attention to control of movement. 
x 
Montreal Cognitive Assessment (MoCA) 
x 
Trailmaking Test – paper based test where the person must “connect the dots” between 
numbers or between alternating letters and numbers. 
x 
Sleep quality assessed by the Pittsburgh Sleep Quality Index, which is a questionnaire 
about sleep-related habits and experiences. 
Following the screening visit, study staff will evaluate performance/responses relative to the 
study enrollment inclusion/exclusion criteria. BMI will be calculated from the height and weight 
collected. Medical records may be examined to verify absence of exclusion diagnoses, to obtain 
complete/accurate medication lists, and to assess whether participants have successfully 
completed prior MRI scans. Individuals who meet all criteria will be invited to enroll in the full 
study. Participants who screen out of MRI may also be invited to enroll for the study with the 
MRI portion excluded. 
At the discretion of the Principal Investigator, any individual may be deemed ineligible for further 
participation in this study if there are concerns about the individual’s capability to perform study 
procedures or if it may be unsafe for the volunteer to participate in the study.  Furthermore, 
minor exceptions to the inclusion/exclusion criteria may be permitted at the discretion of the 
Principal Investigator if those exceptions do not influence participant safety. For example, if a 
participant walks somewhat faster than the target inclusion criteria for walking speed. This is 
important to ensure that individuals are not excluded for insignificant reasons and to facilitate 
meeting enrollment benchmarks. 
___________________________________________________________________________ 
 
Baseline Visit(s) 
Various assessments of walking performance and neural control will be made during the 
obstacle walking task or while at rest.  Other walking tasks will also be assessed, including 
“complex” tasks such as walking while carrying a tray, walking backwards, walking while 
performing a cognitive task (such as naming words beginning with a certain letter), walking fast, 
and combinations of multiple tasks. Tests of gait will be performed on our CIRFace walkway, 
which measure parameters such as step length and swing time. Tasks will include straight walk, 
90 degree turns, 180 degree turns and 360 degree turns. A computer-based cognitive function 
assessment will be administered. 

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Biomechanics and movement data
Performance on walking tests will be assessed using motion 
analysis instrumentation such as force plates, motion capture 
camera, and/or an electronic walkway. When motion capture 
cameras are used, we will tape small reflective markers to the 
participant’s body which are visible to the camera and allow offline 
calculation of joint movements. 
fNIRS prefrontal activation
Prefrontal brain activity may be measured with fNIRS during 
walking and cognitive assessments. fNIRS is a safe non-invasive 
technology for indirectly assessing cortical activation based on 
changes in blood flow and oxygenation. Sensors are held in place 
on the forehead by a headband, and produce infrared light that is able to pass through the skull 
and is absorbed or reflected by blood and other tissues in the head. Infrared light is considered 
safe and there is no sensation association with this procedure.  Calculations made from the 
relative amount of light absorption/reflection provide an estimate of the metabolic activity level of 
underlying cortical tissue. We will use a commercially available fNIRS monitor (Octamon by 
Artinis Medical Systems).
Skin conductance
Skin conductance detects changes in activity of the sympathetic nervous system (fight or flight 
system) that occur when a person feels task-related acute stress. Skin conductance is 
increased with “nervous sweating” on the palmar surface of the hand. For example, walking 
over obstacles has been shown to elicit a larger skin conductance response compared to typical 
walking. Adhesive electrodes are placed on the palmar surface of two fingers on each hand. 
These electrodes are attached by a wire to small control unit worn on a belt.
Video, photos, and voice recordings
During this study, videos and/or photos may be taken during to document the functional abilities 
of participants, and for possible use in research presentations or education. We may also use 
voice recordings to capture performance on cognitive assessments such as a verbal fluency 
task performed during walking. At the time of consent, participants will choose what their 
videos/photos/recordings can be used for. We will avoid capturing images of the participants’ 
faces, and will obscure or delete any such images.
Magnetic Resonance Imaging (MRI)
We will use multiple MRI to assess brain structure, resting state functional connectivity, and 
task-based connectivity during imagined walking. MRI testing on eligible participants will be 
performed at the McKnight Brain Institute on an MRI scanner with a 32 channel head coil. 
Participants will first be directed to a waiting room to complete an MRI safety screening. The 
participant’s answers to this safety screening will be reviewed and approved by the MR 
technician. For all scans, participants will be instructed to remain awake and alert. For functional 
MRI during imagined walking, participants will be asked to imagine walking on the obstacle 
course shown in Figure 1 and over flat ground. Following the MRI we will use the “Vividness of 
Imagined Walking Questionnaire” to assess if the participant was able to imagine the task well.
Blood Draw
Blood draws will be conducted by a trained phlebotomist in the UF Center for Cognitive Aging 
and Memory (CAM) phlebotomy lab in the McKnight Brain Institute (MBI). Up to 45 milliliters of 
fNIRS headband

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blood will be drawn and processed by the phlebotomist in order to collect enough serum to be 
placed in 12 cryovials that will be stored in a -80 degree freezer also housed in the CAM lab at 
MBI (room LG-192). 2.5 milliliters of blood will be drawn directly into a PaxGene tube for genetic 
testing, with the primary goal of assessing polymorphisms in BDNF and COMT. 
Cognitive Function Assessment 
We will administer the Cognitive Assessment Battery from Creyos Research, formerly 
Cambridge Brain Sciences. The assessments currently remain named Cambridge Brain 
Science Assessment, which includes up to 12 cognitive tests.  All are short, simple, computer-
based assessment that assess domains of cognitive such as spatial working memory, response 
inhibition, and reasoning. Specific examples include: 
x 
Digit Span Test –determine the longest list of numbers that a person can remember. 
x 
Visuospatial working memory –remember the sequence and location of items that 
appear and disappear from the screen.  
 
___________________________________________________________________________ 
 
Locomotor Learning Visits 
 
Description of Locomotor Learning Task 
Each of the four locomotor learning sessions will include 20 minutes of actual task practice. 
Short rest breaks are built in throughout this period, and participants will also be allowed to take 
additional rest breaks as often as they wish. Participants will wear a gait belt around their waist 
during this task, which allows research staff to more easily grip and assist a participant if he/she 
becomes unsteady. The sessions will be scheduled approximately equally over two weeks. To 
optimize learning and retention, we will use a tiered approach for task practice which includes 
blocked practice for Session 1, random practice for Session 2, combined practice for Session 3, 
and full course practice for Session 4.  Blocked practice means that one isolated component of 
the task (e.g., transitioning between soft and hard surfaces) will be practiced before moving onto 
another isolated component (e.g., stepping over single obstacles), and then another (e.g., 
stepping over double-height obstacles). Random practice means that the aforementioned 
isolated components will each be practiced multiple times, but interspersed in a random order. 
Combined practice means that the components will no longer be practiced in isolation, but 
rather will be combined such as stepping over and obstacle during the transition between soft 
and hard surfaces. Full course practice means that the participant will practice on the actual 
course that is used for assessment, at both slower and fast speeds. This tiered approach to 
learning ensures that participants attain full understanding and mastery of each component 
early on. As mastery of the basic components is achieved, the complexity and attentional 
demands of the task are increased to promote robust learning and offline consolidation. 

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tDCS during Locomotor Learning 
Participants will be randomized to receive either 
active or sham tDCS, which will be delivered 
simultaneously during the locomotor learning 
task. A commercially available tDCS unit 
(Soterix Medical Inc.) will be used for delivery of 
stimulation. The unit will be carried inside of a 
backpack so that stimulation can be delivered 
during walking. The tDCS unit is very 
lightweight, so wearing it in a backpack adds no 
appreciable effort to the walking tasks.  
Electrode preparation will involve saturating a 
sponge electrode with exactly 10cc of 0.9% 
saline solution using marked syringe (5cc/side). Electrodes will be placed using lightweight 
plastic “headgear” that is adjustable for head size and can hold the electrode montage in place 
during stimulation. We have considerable experience delivering this exact tDCS protocol during 
walking in our ongoing research studies.  
Active tDCS: Twenty minutes of 2.0mA direct current through two biocarbon rubber electrodes 
encased in saline soaked 5cm2 sponges placed over the frontal cortices at F3 and F4 (based 
on the international “10-20 system” of standardized brain electrode placement). 2.0mA was 
chosen based on prior research. 
Sham tDCS: Sham stimulation is performed with the same device and all procedures will be 
identical except for the duration of stimulation. Participants will receive 30 seconds of 2.0mA of 
direct current stimulation at the beginning of each rehabilitation session. Since participants 
habituate to the sensation of tDCS within 30-60 seconds of stimulation, this procedure provides 
the same sensation of active tDCS. 
___________________________________________________________________________ 
Post Visits 
 
Participants will return to lab approximately 1 day, 1 week, and 1 month after completing the 
locomotor learning protocol. These visits will be very similar to the baseline visit, including each 
of the components listed above in that section. At each visit they will walk over the obstacle 
course again to assess changes in performance. At the 1 week and 1 month visits the cognitive 
function assessment will be repeated.  At the 1 week post visit the MRI protocol and/or blood 
draw protocol will be repeated (except for the 2.5ml PaxGene, which is only needed at baseline) 
depending on MRI eligibility. 
___________________________________________________________________________ 
 
Possible Discomforts and Risks: 
As with all physical activity, there is a risk of falling while we test or train walking ability. Falls can 
lead to injuries ranging from minor to serious. It is also possible that participants could experience 
musculoskeletal injury such as an ankle sprain. It is possible that the participant may experience 
fatigue, soreness, and discomfort due to physical activity associated with this study. These are 
unlikely to be worse than what he/she would experience due to increased physical activity outside 
of our study. These are normal responses to exercise and most discomfort would generally 
disappear within a matter of days.  In general, walking exercise is strongly recommended for all 
adults, including elderly adults with medical conditions.  

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There is a risk that participants may find cognitive and functional tests challenging or 
uncomfortable if they have difficulty succeeding with the tasks.  Participant may feel embarrassed 
if they perform poorly on cognitive tests. Participants may skip any question that they do not wish 
to respond do. 
Transcranial direct current stimulation (tDCS) has been used by many prior studies and has an 
excellent record of safety and tolerability. The most often reported effect is tingling or itching 
sensations at the site of electrode placement, which may be accompanied by redness of the skin.  
Some people also report headache or a feeling of fatigue.  All of these effects dissipate quickly, 
and tDCS has not been reported to have prolonged negative consequences.  A recent literature 
review article compiled data from all tDCS clinical studies performed from 1998 to August 2010.  
Of 209 studies (172 articles, encompassing almost 4000 subjects), active tDCS and sham tDCS 
did not differ in the frequency of adverse effects that were observed. The most common adverse 
effects were headache, itching, burning sensation (without actual injury), discomfort and tingling, 
occurring in 10-40% of patients regardless of treatment group. 
Magnetic resonance imaging is considered a safe, and there are no known long term effects 
from short term exposure to magnetic fields. The primary risk is to people with implanted 
metallic objects or medical devices, which could move or heat up as a result of the magnetic 
field. This could cause injury or discomfort. We will screen our participants carefully to ensure 
that no metal objects are present in or on their bodies. Another risk is that metal objects within 
the MRI testing area could become projectiles. We will be careful to ensure that no metal 
objects are present in the testing area. Some participants report claustrophobia while inside the 
scanner. Participants are screened for known claustrophobia before participating (and this is a 
contraindication for participation). If a participant begins to experience symptoms of 
claustrophobia during the scan, they will have the option of discontinuing the scan at any time. 
The scanner produces a loud noise, so participants will be provided with earplugs and/or MR-
compatible headphones to alleviate any potential discomfort or possible hearing damage due to 
this loud noise. 
fNIRS is considered safe. The infrared light used in assessment is not known to cause any harm 
or to alter the brain in any way.  The sensors are secured to the participant’s head using adhesive 
tape, which may cause minor skin irritation in some people, particularly those who are 
sensitive/allergic to adhesives.  We will check with participants about any known sensitivities to 
adhesives. 
Skin conductance involves placing adhesive electrodes on two fingers of each hand. It is 
sometimes slightly uncomfortable to remove the electrodes because they are very sticky. 
The risks of drawing blood from a vein include discomfort at the site of puncture; possible 
bruising and swelling around the puncture site; rarely an infection; and, uncommonly, faintness 
from the procedure. There is also a risk of breach of confidentiality with regard to the data and 
samples collected. In order to minimize risks associated with the blood draw, samples will be 
obtained by a licensed phlebotomist using aseptic technique. A number of steps are taken to 
protect the participant’s privacy. The collected information will be stored electronically with 
restricted access and password protection. Only approved research staff have password access 
to the database. Participant test results from the blood draws will be assigned a unique 
identification number, with the key linking sample numbers to study participant information kept 
in a separate location (i.e. on a restricted access server). 
 
8. Possible Benefits: 
 
There is no direct benefit to the participant. 
 

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9. Conflict of Interest: 
 
None. 
 
10. Statistical analysis and sample size calculations 
 
For Specific Aim 1 we seek to determine whether active tDCS is superior to sham tDCS for 
enhancing retention of locomotor learning after one week. The primary outcome is the change in 
walking speed on the obstacle course between the end of the learning period to the one week 
post visit. We are powering the study to detect group differences in retention of walking 
performance. We will use an ANOVA model to test group differences, and will account for 
demographic covariates. To estimate sample size for this aim, we have conducted a pilot study 
with 12 older adult participants who were randomized to an active (n=5) or sham (n=7) tDCS 
group. To assess retention, the mean walking speed from the final three trials of the learning 
session were compared to the mean walking speed from the three retention trials measured one 
week later. The active tDCS group showed a between-session gain in walking speed of nearly 
0.07 m/s. The sham tDCS group showed a drop in between-session speed of approximately -
0.04 m/s. This between group-difference of 0.1 m/s is considered clinically meaningful and had 
a large effect size of 0.87. The whole-group standard deviation of response was 0.12. Based on 
these preliminary data, we will need 48 participants (n=24 per group) to detect a statistically 
significant group difference at alpha=0.05 and beta=0.20 (i.e., 80% power). To be conservative, 
we will enroll 60 participants to account for potential dropout and to ensure sufficient statistical 
power. 
 
For Specific Aim 2 we seek to determine if several key measures of brain integrity/function help 
to explain individual differences in the retention of locomotor learning after one week. We will 
use multivariate regression models that account for demographic covariates. Based on the 
assumptions of univariate linear regression, a sample size of 60 with alpha=0.05 and beta=0.20 
(i.e., 80% power) will allow us to significantly detect correlations coefficients as small as 0.355.  
Values below this level are generally considered very weak, and thus there would be little 
benefit to powering the study to detect smaller values. Based on our pilot data and findings from 
the literature, we are very likely to observe stronger associations that will achieve statistical 
significance. For instance, our pilot data show that working memory performance and prefrontal 
activation are associated with visuomotor learning with correlations of 0.57 and 0.48, 
respectively. Our pilot data also show that resting state default mode network connectivity is 
associated with retention of learning with a correlation of 0.46. Our statistical models will 
account for a number of demographic and other covariates, thereby accounting for some of the 
variability in the data set and improving our ability to detect these mechanism-related 
associations. 
 
For Specific Aim 3 we seek to acquire evidence that tDCS modifies resting state network 
connectivity and segregation during motor learning. Prior studies have shown that even a single 
session of motor learning or a single session of tDCS can modify the connectivity of resting 
state brain networks. However, this remains an exploratory aim and we have not specifically 
powered the study for this purpose. Nevertheless, as with the other measures described above, 
if the effect size is moderate or large we are likely to detect it with statistical significance. 
____________________________________________________________________________ 
Data and Safety Monitoring Plan 
Adverse Event Reporting 
Adverse events will be reported according to the guidelines of the University of Florida 
Institutional Review.  

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Reporting within 5 days of the PI becoming aware will apply to adverse events that meet all of 
the following criteria: 
x 
Serious 
x 
Unexpected 
x 
Related or the Relationship is “more likely than not”  
 
Adverse events will be added to the cumulative event table and reported at continuing review 
when they meet either of the following criteria: 
x 
Serious (but expected) and related or the relationship is “more likely than not”. 
x 
Unexpected (but not serious) and related or the relationship is “more likely than not”. 
A serious adverse event is any adverse event that results in any of the following outcomes:   
x 
death,  
x 
a life-threatening adverse event,  
x 
inpatient hospitalization or prolonging existing hospitalization,  
x 
a persistent or significant disability/incapacity,  
x 
or a congenital anomaly/birth defect.   
Important medical events that may not result in death, be life-threatening, or require 
hospitalization may be considered a serious adverse event when the event may jeopardize the 
patient or subject and/or may require medical or surgical intervention to prevent one of the 
outcomes listed in the definition above. 
An unexpected adverse event is any adverse event that is not consistent with the current 
investigator brochure, protocol, consent form, or is not part of the normal disease progression.  
In addition, known adverse events may occur more frequently than expected.  If so, then this 
meets the definition of “unexpected” and must be reported to the IRB. 
Protection Against Risk 
Staff training:  All personnel will be thoroughly trained in the study procedures by the Principal 
Investigator or other appropriate member of the research team, and will complete all required 
trainings concerning human subjects research at the University of Florida. 
Health monitoring and medical response: Volunteers at risk of health problems due to recent 
history of medical conditions (e.g., serious cardiac or pulmonary conditions) will be excluded, as 
noted above in the inclusion/exclusion criteria.  Any adverse events will be recorded and 
monitored as required by our University of Florida Institutional Review Board. In the event of a 
medical emergency at the VA Hospital (our study site) we will call the hospital emergency 
response line, 6-9-1-1 and alert them to a code blue (medical emergency). Subjects will be able 
to terminate a study session at their request at any time without prejudice. Minimization of risk 
during neurorehabilitation and assessments will be accomplished by monitoring vital signs, with 
prescribed criteria for termination of the testing session.  Vital signs will be monitored before, 
during and after assessment.  Contraindications for participation will include resting heart rate 
>100 bpm or <50 bpm, resting systolic blood pressure >180 mmHg or <100 mm Hg or resting 
diastolic blood pressure >100 mmHg.  Indications to terminate physical activity will include 
subject complaints of shortness of breath, light-headedness, dizziness, confusion, severe 
headache, dyspnea or onset of angina. If any of these conditions are greater than mild or persist 
after rest, the patient’s primary physician will be called and patient referred for evaluation. If the 
patient complains of angina at rest, loss of consciousness occurs, or cardiac arrest, emergency 
medical services through 911 will be called immediately.  Portable defibrillators are available. 

Protocol #:  IRB201803010 
Page 12 of 12 
IRB version:  03.09.04 
PI version:   10/23/2023 
Confidentiality:  Data will be used only in aggregate and no identifying characteristics of 
individuals will be published or presented. Confidentiality of data will be maintained by using 
research identification numbers that uniquely identify each individual. Safeguards will be 
established to ensure the security and privacy of participants’ study records. Appropriate 
measures will be taken to prevent unauthorized use of study information. Data other than 
demographic information will not use names as an identifier. The research ID number will be 
used. The research records will be kept in a locked room in the study site. The files matching 
participants' names and demographic information with research ID numbers will be kept in a 
locked file that uses a different key from that of all other files. Only trained and certified study 
personnel will have access to these files, and they will be asked to sign a document that they 
agree to maintain the confidentiality of the information.  Electronic records will be stored on 
password protected network server maintained by the university information technology 
department.  In compliance with the Health Insurance Portability and Accountability Act (HIPAA) 
and the Standards for Privacy of Individually Identifiable Health Information of the Department of 
Health and Human Services, we access personal health information and medical records only 
after receiving signed informed consent. 
REDCap: VA REDCap will be used to store de-identified data for increased efficiency and 
secure access by approved staff. This will eliminate the need for storage of written records, all 
data will be accessible in one secure location. REDCap is a secure database only accessible by 
authorized staff onsite from a VA connected computer password protected and maintained by 
VA OIT. 
Safety during walking:  The intensity and duration of walking activity will be carefully monitored 
to ensure that it is appropriate to the participant’s capabilities. Participants will wear a gait belt 
during walking, which will better enable the therapist and/or assistants to provide support in the 
event of a loss of balance.  Falls will be tracked and reported to the PI and IRB even if there is 
no injury associated. 
tDCS Safety:  Our protocol uses stimulation parameters that are considered standard practice, 
and have been used safely in prior research. The most common side effects of tDCS are slight 
itching, tingling, and reddening of the skin under the electrode. Participants typically habituate to 
itching or tingling sensations within 60 seconds of stimulation. To minimize risk associated with 
tDCS, participants will be monitored throughout stimulation sessions and asked to report any 
discomfort. If stimulation sensation is uncomfortable, the stimulation levels will be decreased to 
a comfortable level or will be stopped. 
fNIRS Safety: fNIRS poses no safety risk. Infrared light from the fNIRS device is not harmful and 
elicits no sensation. Sensors may be secured to the skin using adhesive tape, which could lead 
to mild skin irritation in those who are sensitive to adhesives. If a person indicates or displays 
such a sensitivity, we will avoid using adhesive tape and instead use elastic fabric or straps to 
secure the sensors. 
Questionnaire administration: Questionnaire data are collected in secure spaces where the 
interview cannot be overheard. Participants will be informed that they are not required to answer 
questions that they do not wish to answer.