Automatic calibration of electrode arrays for dexterous neuroprostheses: a review

Abstract

Background: Electrode arrays can simplify the modulation of shape, size, and position for 
customized stimulation delivery. However, the intricacy in achieving the desired outcome 
stems from optimizing for the myriad of possible electrode combinations and stimulation 
parameters to account for varying physiology across users.

Objective: This study reviews automated calibration algorithms that perform such an 
optimization to realize hand function tasks. Comparing such algorithms for their calibration 
effort, functional outcome, and clinical acceptance can aid with the development of better 
algorithms and address technological challenges in their implementation.

Methods: A systematic search was conducted across major electronic databases to identify 
relevant articles. The search yielded 36 suitable articles; among them, 14 articles that met the 
inclusion criteria were considered for the review.

Results: Studies have demonstrated the realization of several hand function tasks and 
individual digit control using automatic calibration algorithms. These algorithms significantly 
improved calibration time and functional outcomes across healthy and people with neurological 
deficits. Also, electrode profiling performed via automated algorithms was very similar to a 
trained rehabilitation expert. Additionally, emphasis must be given to collecting subject-specific a priori data to improve the optimization routine and simplify calibration effort.

Conclusion: With significantly shorter calibration time, delivering personalized stimulation, 
and obviating the need for an expert, automated algorithms demonstrate the potential for home-based rehabilitation for improved user independence and acceptance.

Grasp Assessment for Neuroprostheses-Mediated Functions

“…Furthermore, the sensorized glove, which mounted flex and force sensors, measured digit motion and force exerted during ADL-based grasps [22]. These electrophysiological evaluations can help identify stimulation waveform parameters for a desired target response and further optimizations on them can improve subject-specific outcome [27][28][29][30].…”

Electrode configurations for transcutaneous stimulation of forearm muscles

“…Incorporating several electrode combinations also complicates the switching circuits. As in Table I, identifying the optimal distance between the electrodes simpli es electrode calibration and placement routines [25].…”

Field Shaping for Transcutaneous Stimulation of Peripheral Nerves

“…Similarly, stimulation delivered via multi-pad electrodes delayed the occurrence of fatigue [57]. Additionally, the use of multipolar configuration can help to compensate for shifts in electrode displacement [7,58,59].…”

“…Despite the inter-subject variability due to nerve depth and fat thickness, studies have achieved the desired muscle response with suitable electrode configurations that facilitated selective field generation. Optimization algorithms can help to identify suitable electrode locations and configurations to evoke the target response [59,62,63].…”

“…Still, advances in electronics and switching circuits are improving the control of electrode arrays with multiple current sources. Also, the calibration time with electrode arrays can be simplified by automated algorithms [59]. Moreover, field-shaping strategies can improve transcutaneous stimulation when combined with advances in stimulation techniques, electrode configurations, material properties, and interface layers.…”