Resting State Neurophysiology of Agonist Antagonist Myoneural Interface in Transtibial Amputees

The agonist-antagonist myoneural interface (AMI) is a novel amputation surgery that preserves sensorimotor signaling mechanisms of the central-peripheral nervous systems. Our first neuroimaging study investigating AMI subjects focused on task-based neural signatures, and showed evidence of proprioceptive feedback to the central nervous system. The study of spontaneous neural activity in the brain at rest helps non-invasively characterize the spatially distributed networks that prime task response. In this first study on resting state fMRI in subjects with an AMI amputation, we compared resting state functional connectivity in patients with transtibial AMI amputation $(\mathrm{n}=12)$ and transtibial traditional amputation $(\mathrm{n}=7)$ , as well as biologically intact control subjects $\boldsymbol{(\mathrm{n}=10)}$ . We hypothesized that the AMI surgery will induce functional network reorganization that significantly differs from the traditional amputation surgery and also more closely resembles the neural configuration of controls. We found that the neurophysiology of AMI subjects reconfigured in such a way that implicated both a salience network and motor cortex region in relationships with significantly less coupling than in subjects with traditional amputation. We also found that the neuropathological signatures found in the spontaneous networks of traditional amputees decrease in the topology of AMI subjects, producing a connectivity pattern more closely resembling controls. These findings provide researchers and clinicians with a critical mechanistic understanding of the effects of the AMI surgery on the brain at rest, informing future research towards improved prosthetic control and embodiment.