Investigating the Influence of Upper Limb Movements on Lower Limb Neuroplasticity in Humans

This dissertation investigates the influence of upper limb (UL) movements on lower limb (LL) neuroplasticity in humans, with a focus on both healthy individuals and those with chronic stroke. Using neurophysiological tools to assess spinal and cortical excitability, the studies examined whether UL activity modulates LL neuromotor function through interlimb neural coupling. In healthy adults, a novel UL movement paradigm was found to alter spinal excitability, suggesting shared pathways for coordinated motor control. While no uniform group-level effects were observed, unsupervised clustering revealed distinct facilitatory and inhibitory subgroups, highlighting consistent patterns of bidirectional modulation. These findings challenge the traditional assumption that UL activity uniformly suppresses LL reflexes, instead pointing toward individualized spinal network responsiveness. Applying the same paradigm to individuals with chronic stroke revealed that residual interlimb connectivity can influence both spinal and cortical excitability, although with notable interindividual variability. Specifically, rhythmic, symmetric UL movements significantly enhanced paretic leg strength and prolonged cortical silent period duration, indicating supraspinal engagement with therapeutic potential. Although spinal effects were less consistent, a subset of participants demonstrated responsiveness, underscoring the importance of individualized assessment in clinical populations. Together, these findings highlight the plastic potential of spinal and supraspinal pathways, suggesting that UL movement may serve as a novel priming strategy to facilitate LL motor recovery post-stroke. By advancing mechanistic understanding of interlimb interactions, this work underscores the clinical relevance of harnessing UL activity to promote neuroplasticity and functional rehabilitation. Importantly, the consistent observation of substantial individual variability across both healthy and stroke cohorts emphasizes the need for personalized approaches to neuromodulation. This dissertation thus provides proof-of-concept for integrating UL movement into rehabilitation frameworks and lays the groundwork for future studies on dosing, durability, and combination strategies to optimize recovery outcomes.

Author dc:creator

• Aditi Digish Doshi (23291359)

• Neuroscience
• Rehabilitation science
• Physical therapy
• Neurology
• Kinesiology

Statement dc:rights

• In Copyright

DOI dc:identifier

https://doi.org/10.25417/uic.31451110.v1

OAI identifier oai:identifier

oai:figshare.com:article/31451110