Overview

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.

Eligibility

Inclusion Criteria:

1. Healthy adults aged 18-35 years
2. Right-handed (per Edinburgh Handedness Inventory)
3. Normal or corrected-to-normal vision and hearing
4. Eligible for non-invasive brain stimulation per safety screening (no contraindications to TMS)
5. Able to understand study procedures and provide written informed consent in Chinese
6. Willing to comply with all study visits and tasks, including TBS/rTMS and motor practice
7. For yoked pairing: able to be matched to a counterpart participant for practice parameters

Exclusion Criteria:

1. History of epilepsy, seizures, or unexplained fainting; family history of epilepsy in first-degree relatives
2. Any intracranial metal or implanted medical devices (e.g., cochlear implant, deep brain stimulator, aneurysm clips); non-removable metallic objects in head/neck
3. Cardiac pacemaker or other implanted electronic devices
4. Current or past major neurological or psychiatric disorders (e.g., stroke, traumatic brain injury, multiple sclerosis, major depression, bipolar disorder, schizophrenia)
5. Current use of medications lowering seizure threshold or affecting cortical excitability (e.g., tricyclic antidepressants, bupropion, clozapine, lithium, stimulant or sedative-hypnotic abuse); or unstable psychotropic regimens
6. Active migraine with aura or chronic severe headaches
7. Pregnancy or planning pregnancy during participation; breastfeeding (if your site policy excludes)
8. Substance or alcohol use disorder within the past 12 months; positive alcohol/drug screen on visit days
9. Sleep deprivation (<5 hours) on the day before stimulation, or excessive caffeine (>400 mg) within 6 hours pre-stimulation
10. Dermatologic conditions or open wounds at stimulation or EMG/electrode sites
11. Prior extensive training on the specific motor task used in this study (risk of ceiling effects)
12. Concurrent participation in another interventional study or received brain stimulation (TMS/tDCS) within the past 3 months
13. Any condition that, in the investigator's judgment, makes participation unsafe or data unreliable