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Fig. 2 | Journal of NeuroEngineering and Rehabilitation

Fig. 2

From: Discriminability of multiple cutaneous and proprioceptive hand percepts evoked by intraneural stimulation with Utah slanted electrode arrays in human amputees

Fig. 2

Location discrimination trials. Each sub-figure depicts the location of electrodes which evoked different hand sensations, as well as a confusion matrix showing the discrimination performance, and the overall accuracy relative to chance. Full descriptions of the percepts are presented next to the image of the hand and are abbreviated to the bold word in the confusion matrix. Confusion matrices are square, such that the correct answers lie along the diagonal. Asterisks over the bar plot indicates statistical significance with regards to the aggregate data (primary outcome measure). Asterisks overlaid on the confusion matrix indicate statistical significance with regards to an individual condition (secondard outcome measure with limited statistical power). a Subject S3 successfully discriminated among percepts evoked via individual stimulation of four different ulnar-nerve-USEA electrodes, as well as simultaneous stimulation of all four electrodes (four categories shown, the fifth category was concurrent perception at all four locations; 35/35 successful trials, p < 0.0001, binomial test). b Subject S3 also discriminated successfully between individual stimulation of two ulnar-nerve-USEA electrodes (separate solid arrows), as well as simultaneous interleaved stimulation (same as solid arrows) and interleaved stimulation (solid arrows plus dotted arrow) of the same two ulnar-nerve-USEA electrodes. Interleaved stimulation (2.5-ms time shift difference, 200 Hz) reproduced the original percepts simultaneously with no merging sensation, whereas simultaneous stimulation (no time shift difference, 200 Hz) produced both of these percepts accompanied by an merging sensation between them (20/24 successful trials, p < 0.0001, binomial tests). Timing of individual stimulation pulses is shown as a raster plot to the left of the hand. c Subject S4 discriminated among eight different stimulation configurations: individual stimulation of each of three ulnar-nerve-USEA electrodes, simultaneous combined stimulation using different subsets of two of these three electrodes, simultaneous combined stimulation using all three electrodes, and no stimulation (11/24 correct trials, p < 0.0001, binomial test). Importantly, these trials with S4 also included a condition of “no stimulation,” which was identified with 100% accuracy, indicating that percepts were indeed evoked by USEA stimulation (in contrast to pseudesthesia). These three experiments also demonstrate the selectivity of USEA-electrode stimulation, with unique percepts being generated by electrodes as close as 800 μm. * = p < 0.05, ** = p < 0.01, *** = p < 0.001, **** = p < 0.0001; overall binomial test

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