Figure 2
Location and quality of evoked sensations. (A,C) Maps of hand sensations with the four active sites (AS) tested for each subject for amplitude (right) and frequency (left) encoding. Each coloured area indicates the 75th percentile of all the phantom sensations evoked for an AS during the all trial. The maps are related to each implant and are generated by the mapping procedure. For Subject 1, MS-1 (orange area) and MS-2 (red area) were the electrodes #1 AS1 and #2 AS4 implanted, respectively, in the proximal and distal parts of the median nerve; US-1 (blue area) and US-2 (light blue area) were the electrodes #3 AS 6 and #4 AS8 implanted, respectively, in the proximal and distal parts of the ulnar nerve. For Subject 2, MS-1 (orange area) and MS-2 (red area) were the electrodes #1 AS 7 and #2 AS 14 implanted, respectively, in the proximal and distal parts of the median nerve; US-1 (blue area) and US-2 (light blue area) were the electrodes #3 AS 12 and #4 AS 13 implanted, respectively, in the proximal and distal parts of the ulnar nerve. (B,D) Distribution of the sensation type for each subject according to all the phantom sensations evoked by all the AS using both encoding strategies. The bar plots show the qualities of the sensation evoked on a scale from 0 to 5 reported by the subjects during each repetition of the mapping procedure using LAM or LFM in terms of naturalness and pleasantness for the four AS (N = 10 repetitions x 4 AS = 40 for Subject 1 and N = 10 repetitions x 4 AS = 40 for Subject 2). The two-tailed Kruskal-Wallis test did not show a significant difference in the sensation quality between amplitude and frequency modulation in either subject (p > 0.05).
