Poster 1: Joint and Clinical Studies
Functional Imaging Of The Brainstem During Stretch-Evoked Responses Under Different Task Instructions
Rebecca Nikonowicz, Fabrizio Sergi
University of Delaware
Despite the importance of the reticulospinal tract (RST) in motor recovery after lesions of the corticospinal tract, in-vivo measurement of RST function is currently not possible. Because the RST may contribute to the increase in long latency response amplitude (LLRa) associated when participants are asked to “resist” a perturbation, functional magnetic resonance imaging (fMRI) during LLRs under different instructions may be a method to stimulate the RST and decouple the contribution of the corticospinal tract and RST to LLRs. We built an MR-compatible robotic perturbator for experiments with surface electromyography (sEMG) and fMRI. We conducted a preliminary study outside the MRI scanner on five participants using sEMG to measure wrist flexor muscle activity. Participants were given a “Yield” or “Resist” instruction prior to each trial. In a second pilot study, during whole-brain fMRI sequencing, ten participants completed sessions of blocked perturbations under i) Yield, ii) Resist, and iii) Yield 2 (slow perturbation, control) conditions. Analysis of sEMG data shows significantly greater LLRa in “Resist” relative to “Yield” (Resist: 4.483+/-0.966n.u., Yield: 1.205+/-0.964n.u., p=0.001). Analysis of functional images shows increased activation in the brainstem primarily localized in the bilateral medulla and midbrain, contralateral pons, and primary motor cortex in the resist condition.
Research Area: Neuromuscular Modeling & Control