It is estimated that 42 million people in the United States might suffer from some form of movement disorder. Prevailing understandings of these movement disorders characterize "broken" movements in a piecewise fashion, for instance, focusing on motor control, muscle tone, posture, or cognition independently of each other. These fractured approaches to movement coordination are blind to the body's functional integrity. Consequently, rehabilitative interventions target the limb or body parts most affected by the disorder seeking to support the whole body by mending the broken part. However, dexterity is global, functional coordination spanning the whole body. Suprapostural dexterity, for instance, when the task requires an upright posture, is a prime example of how functionality can triumph over anatomical separability. Whatever starts at one or more anatomical areas can swiftly spread throughout the entire body, destabilizing the body on the potential path to task completion. In individuals with movement disorders, the impaired coordination between task engagement and postural instability amplifies the risk of falling. Developing novel rehabilitative interventions to prevent falls and improve the quality of life in individuals with movement disorders thus requires understanding how task completion depends on essential interaction that enables the body to coordinate different anatomical parts.
This project investigates how multiplicative interactions support suprapostural dexterity from two complementary premises. First, movement science has established that postural stability requires a modular structure of functional networks shaped by anatomical constraints. This arrangement indicates a soft assembly and disassembly of functional modules as an individual engages in a task and responds to changing task demands, respectively. Second, movement science has yet to grapple with the multiplicative interactions among movement-system components producing highly complex and unpredictable behaviors beyond the scope of dominant linear modeling approaches. The scientific premises for this proposal are that the dominant network approaches to dexterity are linear, and network approaches can give voice to the nonlinearity we all know is there.
Studying multiplicative interactions among movement-system components and suprapostural dexterity requires innovation in experimental setup and analytical techniques. This project integrates a customizable life-size Trail Making Test (TMT) with posturography, whole-body movement tracking, and eye tracking, along with state-of-the-art cascade modeling and network analysis methods to assess functional coordination across the whole body. The experimenters will leverage causal network analyses of multiplicative interactions instrumental in previous studies of whole-body exploratory motor behavior but not yet utilized in studying suprapostural dexterity.
Specific Aim 1: To investigate how multiplicative interactions among movement-system components support suprapostural dexterity.
Hypothesis 1.1: The experimenters hypothesize that maintaining an upright stance would produce a functional network of multiplicative interactions among movement-system components.
Hypothesis 1.2: The experimenters hypothesize that participating in the Trail Making Test would produce a succession of distinct, modular networks of multiplicative interactions among movement-system components.
Specific Aim 2: To investigate how multiplicative interactions among movement-system components support suprapostural dexterity in the face of postural instability.
Hypothesis 2.1: The experimenters hypothesize that destabilizing contact with the ground surface when maintaining an upright stance will produce modular networks of multiplicative interactions with increased connectivity among these modules compared to stable standing.
Hypothesis 2.2: The experimenters hypothesize that destabilizing contact with the ground surface in the Trail Making Test would produce a succession of distinct, modular networks of multiplicative interactions with increased connectivity among these modules compared to stable standing.
