Bayesian optimization of peripheral intraneural stimulation protocols to evoke distal limb movements.

Objective. Motor neuroprostheses require the identification of stimulation protocols that effectively produce desired movements. Manual search for these protocols can be very time-consuming and often leads to suboptimal solutions, as several stimulation parameters must be personalized for each subject for a variety of target movements. Here, we present an algorithm that efficiently tunes peripheral intraneural stimulation protocols to elicit functionally relevant distal limb movements.Approach. We developed the algorithm using Bayesian Optimization and defined multi-objective functions based on the coordinated recruitment of multiple muscles. We implemented different multi-output Gaussian Processes to model our system and compared their functioning by applying the algorithm offline to data acquired in rats for walking control and in monkeys for hand grasping control. We then performed a preliminary online test in a monkey to experimentally validate the functionality of our method.Main results. Offline, optimal intraneural stimulation protocols for various target motor functions were rapidly identified in both experimental scenarios. Using the model that performed best, the algorithm converged to stimuli that evoked functionally consistent movements with an average number of actions equal to 20% (13% unique) and 20% (16% unique) of the search space size in rats and monkeys, respectively. Online, the algorithm quickly guided the observations to stimuli that elicited functional hand gestures, although more selective motor outputs could have been achieved by refining the objective function used.Significance. These results demonstrate that Bayesian Optimization can reliably and efficiently automate the tuning of peripheral neurostimulation protocols, establishing a translational framework to configure peripheral motor neuroprostheses in clinical applications. The proposed method can potentially be applied to optimize motor functions using other stimulation modalities.