Figure 3. Amputees show characteristic inter-digit overlap patterns during phantom digit movements.

Inter-digit representational similarity of multivoxel patterns underlying the maps shown in Figure 1, derived from a block-design paradigm in amputees (A) and controls (B, D). Similarity (or overlap) is decreased between non-neighbouring digits and tends to increase between digits 3–5, as shown in the controls’ averaged matrix. (C) Positive distribution of inter-subject correlations, between controls’ inter-digit overlap patterns. The grey area indicates the 95% confidence interval (CI) for controls. Pink and blue lines indicate average amputee-to-controls correlations for above and below elbow amputees respectively. Pink and blue shaded areas indicate the corresponding 95% CIs. Both amputee-to-controls correlation averages fell within the normal controls-to-controls correlation range, suggesting that the amputees exhibited a characteristic pattern of inter-digit overlap.

DOI: http://dx.doi.org/10.7554/eLife.15292.011

Figure 3—figure supplement 1. Intact hand inter-digit overlap in amputees.

In order to visualise standard topography in the amputees’ somatosensory cortex, inter-digit representational similarity was assessed for multivoxel patterns underlying the right (intact) hand maps shown in Figure 1—figure supplement 3 in amputees (intact hand, A) and controls (dominant hand, B). To estimate inter-digit representational similarity for the intact hand, the same blocked design as described in the materials and methods section missing hand inter-digit overlap was used. Tactile feedback (from the button box) was incorporated into the task to optimally activate the somatosensory cortex. Participants were instructed to perform single digit button presses (using an MRI-compatible button-box manufactured in house) with their right intact (amputees) or right dominant (controls) hand at a 1 Hz frequency. To cue the participant which digit should be moved, the circle corresponding to this digit flashed at the specified 1 Hz rate. Digits 1–5: thumb; index; middle; ring and little finger.

DOI: http://dx.doi.org/10.7554/eLife.15292.012