Electrotactile feedback outweighs natural feedback in sensory integration during control of grasp force

Shima Gholinezhad, Strahinja Dosen, Jakob Dideriksen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

12 Citations (Scopus)
118 Downloads (Pure)

Abstract

Objective.The nervous system subconsciously estimates the state of the body as a weighted average of the information from various sensory sources, where the weights reflect the perceived reliability of each source. Loss of motor functions can be partially compensated using assistive systems (e.g. prostheses), which may also restore somatosensory feedback through tactile stimulation. Whether such artificial feedback is integrated in the neural state estimation process is not known. Approach.In this study, able-bodied subjects performed a grasp force matching task with supplementary non-invasive electrotactile stimulation with a frequency proportional to grasp force magnitude. Before the task, a brief training session taught the subjects to associate the sensation of electrotactile stimulation with the generated grasp force. In some trials, the force-frequency mapping was biased to introduce an unnoticeable mismatch between natural and electrotactile force feedback, thereby provoking the subject to subconsciously estimate the force as a compromise between the two sources of information. Main results.The outcome of this compromise revealed the weights assigned to each feedback type. The grasp forces were significantly affected by the biased mappings, as indicated by the average estimated relative weights (electrotactile: 0.69 ± 0.29; natural: 0.31 ± 0.29). Across subjects, this weight was correlatedr2=0.75) with the improvement in force matching precision when adding the unbiased electrotactile feedback to the natural force feedback, as predicted by maximum likelihood estimation. This shows that even after minimal training the nervous system adopts electrotactile stimulation as a highly reliable source of information that can improve the precision in the estimation of the grip force. Significance.This result has important implications for the restoration of sensory feedback in upper limb prostheses as it indicates that even non-invasive stimulation can be integrated naturally (i.e. subconsciously and effectively) in the motor controlloop.

Original languageEnglish
Article number056024
JournalJournal of Neural Engineering
Volume18
Issue number5
ISSN1741-2560
DOIs
Publication statusPublished - 7 Sept 2021

Bibliographical note

© 2021 IOP Publishing Ltd.

This work was funded by the Independent Research Fund Denmark, Case Numbers 8022-00243A (ROBIN) and 8022-00226B.

Keywords

  • electrotactile stimulation
  • human-machine interface
  • motor control
  • sensory feedback
  • sensory integration
  • sensory substitution

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