Fig. 3: Percept location varies along somatotopic axes and is determined by underlying RFs. | Nature Biomedical Engineering

Fig. 3: Percept location varies along somatotopic axes and is determined by underlying RFs.

From: Evoking stable and precise tactile sensations via multi-electrode intracortical microstimulation of the somatosensory cortex

Fig. 3: Percept location varies along somatotopic axes and is determined by underlying RFs.The alternative text for this image may have been generated using AI.

a, Example projections of percept centroids in their original position (on array) when projected along either column-wise or row-wise axes. b, Classification performance versus the angle of the projection axis, expressed relative to the local curvature of S1. Each line represents an array for the indicated participant. c, Optimal digit/palmar segment discrimination axis (perpendicular to the projection axis), superimposed on each S1 array (dotted line). The dashed line denotes the local curvature of S1, which, for C1, deviates from the curvature of the central sulcus. d, Digit classification when using either both axes of the array (row and column (2D, two dimensions)) or the best single projected axis (1D, one dimension). e, Within digit, the distance between two PF centroids is significantly correlated with the distance between the electrodes across arrays (Pearson’s correlation, n = 5,892 pairs, r = 0.69, P < 0.0001) and within each array (Pearson’s correlation, r > 0.4, P < 0.0001, Holm–Bonferroni corrected). The dashed lines represent arrays coloured by participant, with the mean and s.d. indicated by the grey line and shaded area, respectively. f, Aggregate PF (red) and RF (blue) for an example electrode from participant P3. g, The size of the RF versus size of the PF for electrodes from participants C1 and P3. The RFs were larger for both participants (two-sided paired t-test, P < 0.0001 and P = 0.0078, respectively). The dashed line indicates unity. h, The proportion of the PF within the RF for all tested electrodes (n = 62 and 25). The median proportion was 1 for both with 25th percentiles of 0.83 and 0.72 for C1 and P3, respectively, suggesting that PFs tended to be completely subsumed by the RF. The box and whiskers show 5th, 25th, 50th, 75th and 95th percentiles. i, The number of regions (digits and palm) encapsulated by each electrode’s RF minus the number of regions encapsulated by its PF for three participants (N = 62, 25 and 21 for participants C1, P3 and R1, respectively). RFs spanned more hand regions than PFs in all three participants (two-sided Wilcoxon rank sum test, P = 0.0035). The bar and whiskers show mean and s.d. *P < 0.0001, **P = 0.0026 and ***P = 0.0035.

Back to article page