Figure 3. Reduced cortical distances between representations of D2 and D3 in older adults.

(A, B) Cortical distances between digit representations in younger and older adults estimated as total (Euclidean) distance (A) and as surface-based (geodesic) distance (B) (mean ± SEM and individual data) (C) Schematic visualization of cortical distance measures. (D) Effect sizes (Hedge’s g and 95% confidence intervals) for Euclidean and geodesic distances. (E) Spatial alignment of younger adults’ (top) and older adults (bottom) digit representations in area 3b displayed in the MNI coordinate system. Line represents linear fit, arrows highlight significant differences in cortical distance between younger and older adults. Shown are data of n = 19 younger adults and n = 17 older adults. See Figure 3—figure supplement 1 for individual plots, and Figure 3—figure supplement 2 for cortical distances using center estimates.

Figure 3—figure supplement 1. Spatial alignment of individual maps.

Spatial alignment of younger adults’ (top) and older adults (bottom) digit representations in area 3b displayed in the MNI coordinate system. Line represents linear fit.

Figure 3—figure supplement 2. Cortical distances based on center estimates.

(A,B) When using center estimates instead of peak vertices as measure for cortical distance, t-tests revealed a trend toward a significant difference in Euclidean distance between D2 and D3 (D2-D3 younger: 5.34 mm ±0.83 mm, older: 2.62 mm ±0.67 mm, p=0.099), and no trend or significant difference for the other finger pairs (D1-D2 younger: 3.38 mm ±0.69 mm, older: 3.36 mm ±0.70 mm, p=0.98; D3-D4 younger: 3.09 mm ±0.41 mm, older: 3.59 mm ±0.45 mm, p=0.41; D4-D5 younger: 9.09 mm ±0.64 mm, older: 10.36 mm ±0.92 mm, p=0.25). Power analyses revealed that a significant effect for the D2-D3 distance would be obtained with slightly higher sample sizes (n = 20 for each group to reach p<0.05 and power of 80%).