Abstract
Multiple sources of sensory information are combined to develop hand posture percepts in the intact system, but the combination of multiple artificial somatosensory percepts by human prosthesis users has not been studied. Here, we report on a case study in which a person with transradial amputation identified prosthetic hand postures using artificial somatosensory feedback. He successfully combined five artificial somatosensory percepts to achieve above-chance performance of 95.0% and 75.7% in identifying four and seven postures, respectively. We studied how artificial somatosensation and the extant hand representation are combined in the decision-making process by providing two mappings between the prosthetic sensor and the location of the sensory percept: (1) congruent, and (2) incongruent. The participant’s ability to combine and engage with the sensory feedback significantly differed between the two conditions. The participant was only able to successfully generalize prior knowledge to novel postures in the congruent mapping. Further, he learned postures more accurately and quickly in the congruent mapping. Finally, he developed an understanding of the relationships between postures in the congruent mapping instead of simply memorizing each individual posture. These experimental results are corroborated by a Bayesian decision-making model which tracked the participant’s learning.
Highlights
Multiple sources of sensory information are combined to develop hand posture percepts in the intact system, but the combination of multiple artificial somatosensory percepts by human prosthesis users has not been studied
We verified in the T session that the identification of hand postures using only artificial somatosensory feedback is possible
We show that five somatosensory percepts can be combined and used to identify hand postures without other sensory information and in the absence of voluntary motor control
Summary
Multiple sources of sensory information are combined to develop hand posture percepts in the intact system, but the combination of multiple artificial somatosensory percepts by human prosthesis users has not been studied. While the mechanics and control strategies for prostheses have advanced rapidly in recent years, current commercial prostheses do not restore the sensory information formerly provided by the hand This lack of somatosensory feedback forces users to rely other sources of feedback, such as vision, to regulate movements[22,23], likely limiting their ability to perform tasks that divert visual attention from the prosthetic device while it is in use. Multiple sources of somatosensory information are combined in order to provide unified perception of objects or grasping interactions[38,39,40,41] This process of combining information varies as a function of the available information[41,42,43], information complexity[44], and the existence or applicability of prior knowledge during functional tasks[44,45,46]. Much of the literature on intact sensorimotor control indicates that this sensory fusion is often a subconscious process whose output is a conscious decision[47,51,52,53,54,55,56,57]
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