UCSF

Many actions involve coordinated movements of multiple body parts. Motor coordination is thought to rely on a hierarchical sequence of computations that transforms overarching movement objectives into specific commands for each body part, but how these hierarchical computations are implemented within anatomical hierarchies remains largely unknown. In Chapter 1, I introduce additional background on motor hierarchies and propose that the motor hierarchy coordinating head-eye gaze shifts could be interrogated in a systematic, stepwise fashion using the genetically tractable mouse model. In Chapter 2, I present work showing that mice make innate, stimulus-evoked gaze movements involving coincident head and eye movements that are mediated by superior colliculus (SC). These findings reveal unexpected flexibility in mouse gaze shifts and provide an experimental paradigm for studying coordinated movement of multiple body parts. In Chapter 3, I present original research that systematically interrogates different levels of the mouse gaze hierarchy. This research unexpectedly reveals that no individual stage of this anatomical hierarchy computes the desired overall displacement. Instead, single SC upper motor neurons specify a mixture of endpoints and displacements for different body parts, with displacements for different body parts computed independently and at distinct anatomical stages.