Abstract
Recent experiments have shown that neural stimulation can successfully restore sensory feedback in upper-limb amputees improving their ability to control the prosthesis. However, the potential advantages of invasive sensory feedback with respect to non-invasive solutions have not been yet identified. Our hypothesis was that a difference would appear when the subject cannot focus all the attention to the use of the prosthesis, but some additional activities require his/her cognitive attention, which is a quite common situation in real-life conditions. To verify this hypothesis, we asked a trans-radial amputee, equipped with a bidirectional hand prosthesis, to perform motor tasks also in combination with a cognitive task. Sensory feedback was provided via intraneural (invasive) or electro-tactile (non-invasive) stimulation. We collected also data related to self-confidence. While both approaches were able to significantly improve the motor performance of the subject when no additional cognitive effort was asked, the manual accuracy was not affected by the cognitive task only when intraneural feedback was provided. The highest self-confidence was obtained when intraneural sensory feedback was provided. Our findings show that intraneural sensory feedback is more robust to dual tasks than non-invasive feedback. This is the first direct comparison between invasive and non-invasive approaches for restoring sensory feedback and it could suggest an advantage of using invasive solutions.Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT02848846.
Highlights
The loss of a hand affects persons’ quality of life (Meyer, 2003)
We provided to the amputee: (i) intraneural sensory feedback (IF) delivering stimulation trains through an implanted TIME in the ulnar nerve, or (ii) electrotactile sensory feedback (SF) delivering electrical stimulation through a surface electrode placed on the residual arm skin or (iii) no sensory feedback (NF)
In order to assess the effect of adding sensory feedback to a hand prosthesis in a dual-task paradigm, we evaluated the memory span among the tested conditions
Summary
The loss of a hand affects persons’ quality of life (Meyer, 2003). Several clinical solutions have been provided compared to the first manufactured prostheses, developing more dexterous artificial hands (Belter et al, 2013). Since daily activities are frequently performed in a “dual-task” paradigm condition (i.e., holding a beer while reading a book) (Land et al, 1999), the execution of motor tasks with a bidirectional prosthesis should be assessed in combination with tasks increasing the cognitive load for the user. To accomplish this dual paradigm the user cannot (or should not) focus all the attention to the use of the prosthesis. Results indicate that only intraneural sensory feedback could allow to achieve a robust improvement in motor performance, maintaining a high STC, in case of increased cognitive load
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