PhD Defense: Action Compositionality with Focus on Neurodevelopmental Disorders

A central question in motor neuroscience is how the Central Nervous System would handle flexibility at the effector level, that is, how the brain would solve the problem coined by Nikolai Bernstein as the ``degrees of freedom (dof) problem". This problem is believed to be solved with a particular dimensionality reduction strategy in which action production would consist of tuning only a few parameters that control and coordinate a small number of motor primitives, and action perception would take place by applying grouping processes that would solve the inverse problem.

Little is known, however, about how words/primitives would be formed from low-level signals measured at each dof. Here we introduce the Spatial Basis-Spatial Temporal (SB-ST) decomposition, a bottom-up approach to find full-body postural primitives as a set of key postures. We showcase the method by applying SB vectors and ST parameters to study vertical jumps of young adults (YAD) typically developing (TD) children and children with Developmental Coordination Disorder (DCD) obtained with motion capture. We also go over a number of other topics related with compositionality: we introduce a top-down system of tool-use primitives based on kinematic events between body parts and objects and discuss the need for custom-made movement measurement strategies to study action primitives on some target populations, for example infants. Still on infant movement measurement, we present an alternative way of processing movement data by using textual descriptions as replacements to the actual movement signals observed from behavioral trials.

In the end, we sketch a conceptual, compositional model of action generation based on exploratory results on the jump data. We discuss the nature of action and actor information representation by analyzing a second dataset with arm-only data (bimanual coordination and object manipulations) with more target populations than in the jump dataset: TD and DCD children, YAD and seniors with and without Parkinson's Disease (PD).

Examining Committee:

Chair: Dr. Yiannis Aloimonos

Dean’s rep: Dr. Jane Clark

Members: Dr. Cornelia Fermuller

Dr. Nicholas Roussopoulos

Dr. James Reggia