This study examined the effect of temporal changes in corticospinal excitability in motor imagery (MI) and the effect of real‐time guides for MI on excitability changes. The MI task involved wrist flexion and motor evoked potentials using transcranial magnetic stimulation were recorded and examined from the flexor carpi radialis. Ballistic (momentary MI) and tonic (continuous MI) conditions were used, and the duration of each MI was different. In Experiment 1, each MI task was performed using an acoustic trigger. In Experiment 2, a real‐time guide was presented on a computer screen, which provided a visual indication of the onset and duration of the MI task through via moving dots on the screen. The results indicate that the corticospinal excitability changed differently, depending on the duration of MI. Additionally, with real‐time guides, the change in corticospinal excitability became clearer. Thus, corticospinal excitability changes due to the temporal specificities of MI, as well as with actual motor output. Moreover, if MI is actively performed without a guide, it is likely to show an unintended change in corticospinal excitability. It is suggested that when MI is performed with visual guide, the excitatory changes of the corticospinal tract might be different from the actual motor output. Therefore, when using MI for mental practices, it is possible to improve the effect of a guide for MI, such as a visual indicator for motor output. Additionally, when examining neural activities in MI, it may be necessary to consider the characteristics of motion performed by MI.
The development of welfare assistive devices for frail elderly people has attracted significant attention for its effort to improve the quality of life and reduce the burden on caregivers. However, it is challenging to conduct multiple user tests because of the significant burden on the elderly; thus, we need efficient ways to extract insight through different approaches. In this study, we aim to elucidate real-time transitions in users’ emotions and achievement motivation while using such a device. We synthesize an utterance analysis method based on attribution theory, in which all users’ utterances are attributed to four categories (ability, effort, task difficulty, and luck) that follow the developed coding rules. Knowing the transitions in causal attribution allows us to extract salient experiences for users, especially by extracting shifts from them and analyzing why the shift occurred and what exactly was happening before and after the shift. If only salient user experiences can be referenced from the aggregate data, useful information can be extracted in a short time to improve system characteristics and the environment. We discussed the validity and reliability of the proposed method by conducting a user test of an electric-assisted four-wheeled cycle for frail elderly people in Kakegawa city in Shizuoka, Japan. We also succeeded in marking the points that need attention, which is about 33% of the total amount of utterance data (1626 utterances), and thus confirmed the potential of the proposed method. Future research should examine how the developed methodology can help designers improve assistive device development, as well as how it can contribute to other fields such as education and social assistance.
[Purpose] This study aimed to investigate how the speed alteration task, which gradually
increases or conversely decreases walking speed, affected walking stability. [Participants
and Methods] Thirteen healthy young adults performed two walking tasks as follows: the
speed alteration task, in which the walking speed was gradually increased or decreased,
and the speed constant task, in which the walking speed was maintained at a comfortable
level. Before and after each task, the Timed Up and Go test was performed to analyze time,
walking speed, and trajectory. The overall score of the Timed Up and Go test, as well as
the scores of the three major segments (i.e., forward, turning around, and return), and
nine subsegments, were calculated and analyzed. [Results] During the speed alteration
task, parameters including time and walking speed of the Timed Up and Go test were
significantly improved. Also, the same parameters increased significantly in the forward
and return segments. These increases were also observed in the first subsegment of the
forward segment and the second subsegment of the return segment. [Conclusion] The speed
alteration task improved walking stability, so it could be used in gait training to
improve walking stability.
[Purpose] This study aimed to examine the difference in the excitability of the primary
motor cortex between initiation-predictive and non-predictive tasks, where the onset of
muscle relaxation is predicted and not predicted, respectively. [Participants and Methods]
Seventeen participants were asked to perform rapid muscle relaxation either through an
initiation-predictive or non-predictive task. The baseline was set at 20 percent of the
maximum voluntary contraction. Motor-evoked potentials and H-reflexes elicited by
transcranial magnetic stimulation and median nerve electrical stimulation, respectively,
were measured. The mean stimulation time from the onset of relaxation was calculated, and
the motor-evoked potentials and Hoffmann’s reflexes elicited during the first (immediately
before relaxation) and second half (long before relaxation) were compared. [Results] The
amplitude of the motor-evoked potential significantly increased in both
initiation-predictive and non-predictive tasks when compared to the baseline, indicating
increased excitability of the primary motor cortex. The motor-evoked potential from the
initiation-non-predictive task, but not the initiation-predictive task, was associated
with increased excitability of the primary motor cortex immediately before relaxation.
[Conclusion] Variations in the predictability of motor movements are associated with
changes in muscle relaxation control in the central nervous system.
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