Participants
Twenty-six patients with subacute to chronic stroke were included (Figure 1). They were allocated to two groups: motivation and control groups. Table 1 presents the general characteristics of the participants. All participants were right-handed, had mild-to-moderate impairment in the upper extremity, and had the motor capability to complete the task using their more-affected arm. The inclusion criteria were as follows: (1) patients with first ever ischemic and hemorrhagic stroke in the either subacute or chronic stage (at least one month after stroke onset), (2) individuals with movement difficulties in the upper limb (Fugl-Meyer Assessment score >=19)[8,21], (3) individuals without communication or intellectual problems (Mini-Mental State Examination, score >= 24), (4) right-handedness (Edinburgh handedness score >=70%), and (5) ability to reach all targets displayed on the touch screen used in the experiment. The exclusion criteria were: (1) Individuals with multiple stroke attacks or who had undergone orthopedic surgery on the upper extremity, and (2) visuomotor neglect as measured by Albert’s test [22]. Participants were randomized into the motivation and control groups, and those in the motivation group completed a training schedule to learn the use of the more-affected arm, while the control group did not. This study was approved by the Institute of Research Board of the Jeonju University(jjIRB–190414–HR–2019-0409). All participants read and signed a written consent form before starting the experiment.
Individualized Motivational Enhancement System (IMES)
We developed a new training system, called the individualized motivation enhancement system (IMES), which changes task difficulty by varying the time limit for reaching movements. IMES comprised a 55” touchscreen, used to provide targets and collect data; a main computer, used to control the overall programs; and a height controllable desk used to adjust the screen to the height of individual participant (Figure 2A). Our system provides game-based test and individualized training sessions requiring participants to catch targets on a 2D touch screen by moving their more or less affected arms (see IMES: test and individualized training sessions below for details). In general, at the beginning of the sessions, the participants were asked to place their index fingers at the home position, which was set 20 cm apart from the xiphoid process of the subject’s trunk. Then, the target appeared in one of the hundred predefined locations (17 angles between 10 to 170 with 20 degrees of the interval, the six different distances between 10- 30 cm with the interval of 5cm)(Figure 2B). The maximum distance of the targets was 50 cm apart from the subject. The participants with stroke were instructed to “catch the target as fast as possible before the targets disappear and then return to the home position.” Each target appeared and disappeared within a predefined time limit. A movement was counted as successful only when the participants succeeded in catching the appeared target within the set time limit. The time limit was altered to control the task difficulty. If the participants succeeded in catching the targets, they earned game scores, which appeared in the top-left corner of the screen for the motivational purpose. The total number of targets and time limits varied across test and training sessions, as explained in the following sections.
IMES: Test session
During the IMES test session, the impairment, performance, and use of the more-affected arm were measured (Figure 2C). 45 targets of out 100 targets were used in the test session (Figure 2B). There were two different conditions: no-time constraint and fast-time constraint. The No-time constraint condition had no time limit; the fast-time constraint condition had an approximately 500 ms time limit for the target reaching. The time limit in the fast-time constraint condition was based on the previous study investigating different movement duration for the targets in different locations [23,24]. Each condition had two blocks: free- and forced-choice blocks. During the free-choice block, the participants freely selected the arm they used. During the forced-choice block, the participants were asked to use only the less-affected (LA) arm and then to use the more-affected (MA) arm to reach all targets. The total number of targets that the participants successfully reached in the free- and forced-choice blocks in the fast-time constraint condition represented the more-affected arm performance and use, respectively [24,25]. Since the participants were informed that there was no correct or wrong answer for free-choice blocks, the spontaneous arm choice pattern (i.e., the use of the more-affected arm) was successfully measured. We also included the forced-choice block in the no-time constraint condition to measure the movement duration for each arm and used each movement duration to designate the time limit for the training session.
IMES: Individualized training session
The IMES training session was designed to provide a customized training protocol based on the individual's functional ability. To achieve this goal, we modulated the time limit. As previously mentioned, the movement duration for each target was measured for each arm during the forced-choice block of the no-time constraint condition in the IMES test session. Movement time was defined as the default time limit with a zero-task difficulty parameter (TDP). TDP was a parameter to modulate the task difficulty by changing time limit for each target so the tester or the participant manipulated the TDP between -50% and +50% with 10% of interval [+- 50, 40, 30,20,10, 0]. If the TDP was set at +10%, the time limit became 10 % longer than the actual movement time of the more affected arm. If the TDP was negative, the time limit was shortened. The time limit differed depending on which arm the participants used. Most patients with stroke showed slow movement times when using their more-affected arm, thus durations of the more- and less-affected arms were measured separately, and these valued were applied during the training. For example, for the target on the left corner, the time limit was 580 ms for the more-affected arm, but 350 ms for the less-affected arm.
The participants were asked to successfully use the more-affected arm to catch the targets as many times as possible using either the more- or less-affected arms during the training sessions. If they missed several targets at the beginning, the tester recommended speeding up or switching arm. In general, the participants completed five training blocks, each consisting of a total of 100 targets, per day unless they felt tired or experienced pain.
Intervention for learning use of the more-affected arm with and without autonomy support
To investigate the effects of autonomy support on the outcome measures (or participants’ behaviors), we randomized the participants into two groups: motivation and control. Participants in the motivation group were able to adjust their task difficulty actively, although they did not exactly recognize how the IMES modulated it. After each training block, the participants were asked whether they wanted to make the task more difficult or not. The time limit became faster or slower in accordance with the participants’ choice for TDP In contrast, the participants in the control group did not have any opportunity to adjust to task difficulties. Instead, it was randomly selected between -20 and +20 for each training block. On the first training day (Day 2), we intentionally set TDP to be more positive than on the other days, as we thought that this would be helpful to prevent the negative failure of using the more-affected arm at the beginning of the training.
We administered the social comparative verbal feedback to only the motivation group. This consisted of phrases such as “the active participant, like you, normally performs well at this type of game.” However, the participants in the control group received only brief plain verbal feedback, such as “good job”.
Experimental protocol
The overall experiment was conducted for five weeks with 11 visits (Figure 2D). Screening examinations were performed at least one week before the experiment. On the first day, the participants who met the inclusion criteria were randomly allocated into two groups. All participants completed the baseline test on Day 1 in the first week, and subsequently underwent IMES test session and clinical assessments. The patients performed the five blocks of the training session during the second to fourth weeks (Days 2-10), each lasting about an hour. The training session was performed three times a week for three weeks. Subjects were asked about the self-efficacy and outcome expectation immediately after each training block. In the last fifth week, a retention test, identical to the baseline test, was conducted (Day 11).
Outcome measurements
The primary outcome was impairment, performance, and use of the more-affected arm measured by both IMES system and clinical tests and the secondary outcome was Participant’s behavior of autonomy support and motivation to use the more-affected arm.
IMES system: measuring impairment(movement duration), performance(forced-choice), use(free-choice) of the more-affected arm in the fast-time constraint condition
The IMES test sessions (baseline and retention tests) measured impairment, performance, and use. Impairment was assessed by the average movement duration of the more-affected arm in seconds (log-transformed) during the forced-choice block of the no-time constrained condition. Performance and use were measured by the total number of successful reaching with the more-affected arm during the forced-choice block and free-choice block of the fast time-constrained condition, respectively (see IMES: test session for more details).
Clinical test: Measuring impairment, performance, use of the more-affected arm
Clinical tests were used to evaluate the changes before and after IMES training at baseline and retention tests. The Fugl-Meyer Assessment for Upper Extremity (FMA) was used to measure impairment. The Wolf motor function test with time domain (WMFT-time) and the actual amount of use with the quality of movement scale (AAUT-QOM) were used to evaluate the performance and amount of use of the more-affected arm, respectively.
We used only 8 of the 17 items in WMFT, which were relevant to reaching movement, and 14 of 17 items in the AAUT, included purposeful UE movements. The sum of each item on the FM and the average time of 8 WMFT items were calculated. The AAUT was scored based on the quality of movement (AAUT-QOM). These clinical tests are standard in stroke rehabilitation, and their validity and reliability have been proven in prior studies.
Participant’s behavior of autonomy support
We focused on two important sub-phases of the training sessions: early (the first two training days) and late (the last two training days) phases to study the changes in TDP, successful/failed experience, and success rate during the training. The average values of these variables were used to compare phase differences.
The TDP, which either the tester or the participant selected, was recorded in each IMES training block across the entire training session. The total number of successful experiences and failures in each IMES training block were counted when the participant used the more-affected arm successfully or unsuccessfully. Success rate was defined as the number of successful uses of the more-affected arm over the total use (success + failure) of the more-affected arm and represented as a percentage.
Measuring motivation to use the more-affected arm
Confidence in the Arm and Hand Movement (CAHM) was used to measure the participant's motivation to use the more-affected arm[11]. The original CAHM was modified to fit the IMES, and the participants’ expectations and confidence while performing the task were measured. SE was the question, "How confident are you when catching an animal character using the more-affected arm?". OE was the question, "If you take animal characters using the more-affected arm in the next block, how many characters can you catch?". We used a scoring board, with the scores for both questions ranging from 0 to 100. Because SE and OE were measured only during the training sessions, the data were obtained from the first and last training days (Days 2 and 10). There were five SE and OE scores per training day, for which the scores were averaged for further analysis.
Blinding
An independent evaluator blinded to participant recruitment, data collection, and group allocation analyzed all outcomes. The participants did not know which group they were in, and they were not allowed to discuss their interventions with each other.
Statistical analysis
All statistical analyses were performed using the R Studio 1.2. and the significance level was set at p<0.05. Mixed-effect linear regression analysis was used to determine the impact of an individualized training program of IMES and clinical and motivational variables. The Test (baseline vs. retention) and group (motivation vs. control) were set as categorical variables of the fixed effect, and each individual was set as a random intercept.Four different analysis models were constructed, as follows: The first two models included one factor only (e.g., Group or Test), and the last two models had two factors with and without interaction terms (e.g., Group + Test for model 3, Group * Test for model 4). The anova function() in R studio was applied for the model comparison and to define the best-fit model with the lowest Akaike information criterion (AIC). Once the best-fit model was selected, the model diagnostics, including visual inspection of outliers via the qq-norm plot, calculated Cohen’s distance. The effect size, measured as omega-squared (w2), was calculated for further information.We used Phase (early vs. late) instead of Test (baseline vs. maintenance) when analyzing participants' autonomy-supporting behavior. To investigate whether changes in successful experience during training sessions were associated with changes in the IMES and clinical and motivational variables, correlation analyses were conducted using Spearman or Pearson methods depending on the data distribution.