Abstract
Motor skill learning is a fundamental aspect of human survival and advancement. This ability to learn and refine motor skills is critical for navigating everyday life and excelling in specialised domains where precision and skill are essential. External stimuli and methodological factors have been shown to influence corticospinal excitability (CSE), a neural marker of motor readiness, to optimise motor skill learning and rehabilitation strategies. The current research focuses on understanding the roles of visual congruency, action observation (AO), motor imagery (MI), movement intention, and stimulation predictability in modulating CSE facilitation.
Experiment 1 examined the role of congruency between observed actions and visual contexts in facilitating CSE, while Experiment 2 investigated how movement intention and handedness influence CSE facilitation during action observation (AO). Results from the first two experiments were found to be non-significant due to an unforeseen confounding variable, predictability. Thus, Experiment 3 examined the influence of stimulation predictability on CSE measurements and addressed predictability as a potential confound in previous studies. Results of Experiment 3 showed that a predictable TMS results in a suppressed CSE; thus, experimental conditions need to be equally predictable. Finally, Experiment 4 explored the interaction between action observation (AO) and motor imagery (MI) in facilitating CSE, testing competing theories: the Dual-Action Simulation Hypothesis (DASH) and the Visual Guidance Hypothesis (VGH). Results from experiment 4 partially supported DASH while not supporting VGH.
Together, these experiments challenge the assumption that AO and MI are universally effective strategies for enhancing motor excitability. Instead, they reveal a more nuanced picture: context, predictability, attention, and individual cognitive effort all play essential roles in determining whether CSE facilitation occurs. While this work also acknowledges methodological limitations (such as variability in participant posture, engagement, and baseline design), it offers concrete paths forward for refining both experimental protocols and applied interventions.