Evaluating Force Deficits During Bimanual Coordination in Parkinson's Disease: Insights from Multimodal Imaging - Parkinson’s disease (PD) is the fastest-growing neurological disorder globally, resulting in debilitating motor impairments and, in some cases, cognitive challenges that significantly disrupt daily life. While current treatments manage symptoms, they do not slow disease progression, partly due to a limited understanding of the brain circuits involved in PD-related motor deficits, especially in complex tasks that reflect real-world challenges. Although much research has concentrated on unimanual movements, everyday activities frequently involve the need for coordinated bimanual actions alongside cognitive demands, such as buttoning a shirt while simultaneously maintaining selective attention during a conversation. People with PD experience exacerbated motor symptoms in dual-task conditions - such as performing mental subtraction while engaging in complex coordinated movements like walking - yet the underlying neural mechanisms driving this interference are poorly understood, particularly in relation to bimanual coordination, which has yet to be thoroughly studied. This study aims to fill a critical knowledge gap by using advanced multimodal imaging to examine force control deficits and associated brain changes in PD during single and dual-task bimanual coordination. We hypothesize that PD will demonstrate altered brain activity during bimanual coordination tasks, with greater disruptions in brain function under dual-task conditions. These disruptions are expected to result in more pronounced motor and cognitive impairments in PD, especially when tasks involve additional cognitive demands. Using functional magnetic resonance imaging (fMRI) and functional near- infrared spectroscopy (fNIRS), we will measure brain activity during isometric bimanual force tasks at low to moderate force levels, both in isolation and while participants engage in cognitive challenges, such as selective attention tasks that require focusing on relevant stimuli while ignoring distractions. fNIRS offers distinct advantages over fMRI, including greater flexibility in participant positioning and the ability to assess brain responses in more naturalistic settings, providing additional insights into cognitive-motor interactions. Furthermore, we will investigate PD-related structural brain changes through diffusion MRI, which when combined with functional measures of neural activity and behavioral performance will allow us to identify predictors of dual- task interference. This research will deepen our understanding of the neural mechanisms underlying bimanual coordination deficits and may guide the development of targeted rehabilitation strategies aimed at improving both motor and cognitive performance.
