Repetitive Transcranial Magnetic Stimulation Primed Self-controlled Practice on Motor Learning

This study aims to investigate the additive effects of combining self-controlled practice with repetitive transcranial magnetic stimulation (rTMS) pretreatment on motivation enhancement and motor learning performance in healthy young adults. According to the "Optimizing Performance Through Intrinsic Motivation and Attention for Learning" (OPTIMAL) theory, numerous studies have demonstrated that providing learners with autonomy during practice can facilitate intrinsic motivation and motor learning. However, self-controlled practice alone may have limited effects, and further interventions may be required to amplify learning outcomes.

In recent years, non-invasive brain stimulation techniques-particularly high-frequency (facilitatory) rTMS applied to the dorsolateral prefrontal cortex (DLPFC)-have been shown to enhance motivational drive and explicit learning performance by strengthening the connectivity of the DLPFC-midbrain dopamine pathway. For example, 10 Hz high-frequency stimulation can significantly improve learners' accuracy and motivation. Interestingly, several sequence learning studies have found that low-frequency (inhibitory) rTMS, when used as a priming intervention, can instead enhance implicit procedural learning. This effect may occur because inhibiting the lateral prefrontal cortex reduces its top-down suppression of implicit learning systems, thereby releasing procedural learning potential.

Based on the theory of metaplasticity, applying facilitatory or inhibitory stimulation beforehand can alter the threshold of synaptic plasticity, thus influencing subsequent learning outcomes. Therefore, this study designed two DLPFC pretreatments-facilitatory and inhibitory-and combined them with self-controlled practice to systematically examine the interaction between different stimulation protocols on motivation and motor learning.

This cross-sectional experiment plans to recruit 72 healthy participants aged 20 or older, randomly assigned to one of six groups: (1) facilitatory rTMS + self-controlled practice, (2) facilitatory rTMS + yoked control, (3) inhibitory rTMS + self-controlled practice, (4) inhibitory rTMS + yoked control, (5) sham rTMS + self-controlled practice, and (6) sham rTMS + yoked control.

The experiment will last for seven days. On Day 1, participants will complete baseline testing, followed by facilitatory rTMS, inhibitory rTMS, or sham stimulation over the DLPFC. Immediately afterward, they will engage in a trajectory-tracking learning task (manipulating a joystick to reproduce a sine-wave pattern). After practice, participants will complete a motivation assessment. During the trajectory-tracking task, the self-controlled group can choose when to receive feedback to adjust their learning, whereas the yoked control group will receive feedback at time points matched to their paired counterpart.

On Day 2, participants will again receive the assigned rTMS (facilitatory, inhibitory, or sham), complete the trajectory-tracking task, and undergo a motivation assessment. After a five-minute rest, they will perform retention and transfer tests, followed by TMS measurement of cortical excitability. On Day 7, participants will return to the laboratory to complete another retention and transfer test, along with cortical excitability measurement via TMS.

The primary behavioral outcomes are the root mean square error (RMSE) and error estimation (EE) in the trajectory-tracking task. Motivation will be assessed using the Intrinsic Motivation Inventory (IMI). As there have been no prior studies combining DLPFC rTMS pretreatment with practice autonomy, the results of this experimental design are expected to provide new insights and references for enhancing motor learning ability in healthy adults.