BME PhD Candidate, Andrea Zonnino, will be defending his dissertation
Robot-assisted imaging of neuromuscular function: new insights on the neuromechanics of interaction control
When: Monday, May 18, 2020
Committee Chair: Fabrizio Sergi, PhD
Committee: Curtis Johnson, PhD, Thomas Buchanan, PhD, Stuart Binder-Macleod, PhD.
Manipulation is a fundamental motor skill as it is the preferred method by which humans physically interact with the outside world. While the control of physical interaction for whole arm movements has been thoroughly studied during the last decades, limited knowledge is available on how physical interaction is controlled in tasks involving distal joints such as the wrist. The lack of knowledge primarily arises from technological limitations that restrict in-vivo measurement of neuromuscular function during manipulation.The main objective of this dissertation was to develop new methods for measuring neuromuscular function thus contributing to elucidate the neuromechanics of physical interaction for hand/wrist tasks.
In Part I, we present research directed to understanding how activation of different muscles is coordinated to accurately perform wrist tasks. Using musculoskeletal modeling, we first established the contribution of superficial and non-superficial muscles in the control of the wrist joint stiffness and torque. Results show how non-superficial muscles play a key role in the control of wrist tasks. Because current measurement methods cannot account for function of these muscles non-invasively, we worked to develop multi-muscle magnetic resonance elastography (MM-MRE), a novel measurement technique to estimate force of all forearm muscles. Two validation experiments, conducted on a cohort of 15 healthy individuals, show how MM-MRE has enough sensitivity to detect change in muscle mechanics produced by the application of isometric wrist torques. Moreover, we show how elastography measurements can be used to estimate muscle force from the complete set of forearm muscles making MM-MRE a promising tool for future research on muscle coordination.
In Part II, we present research directed to measuring brain function associated to long-latency responses (LLR), a feedback mechanism employed by the central nervous system to stabilize interaction with external agents. Toward this goal, we developed and validated StretchfMRI, a technique that combines robotics and simultaneous measurement of electromyography and fMRI, allowing for the first time to study cortical and subcortical function associated to LLRs in humans. We then used StretchfMRI to establish muscle-specific representation of LLR activity in the brainstem, for the first time in-vivo and in humans, in a cohort of 18 healthy individuals. The observed organization is consistent with animal models, with activity primarily in the ipsilateral medulla for flexors and in the contralateral pons for extensors. Although, additional activation can be observed bilaterally in the midbrain and in other pontomedullary areas.