Figure 3.

(a and b) Examples of normalized experimental angular distributions for axonal growth measured on micropatterned PDMS surfaces with different pattern spatial periods d. The continuous red curves in each figure are the predictions of the theoretical model discussed in the main text. The vertical axis (labeled normalized frequency) represents the ratio between the number of axonal segments growing in a given direction and the total number N of axon segments. Each axonal segment is of 20 μm in length (see section “data analysis”). All distributions show data collected at t = 40 h after neuron plating. (a) Angular distribution obtained for N = 1404 different axon segments on surfaces with d = 1 μm. (b) Angular distribution obtained for N = 1560 different axon segments on surfaces with d = 4 μm. The data show that the axons display strong directional alignment along the surface patterns (peaks at $\theta =\pi /2\text{and}\theta =3\pi /2$), with the highest degree of alignment (sharpness of the distribution) measured for d = 4 μm. (c and d) Examples of normalized speed distributions for growth cones measured on micropatterned PDMS surfaces with different pattern spatial period d. (c) Speed distribution for N = 210 different growth cones measured on surfaces with d = 1 μm. (d) Speed distribution for N = 242 different growth cones measured on surfaces with d = 4 μm. The continuous red curves in each figure represent the predictions of the theoretical model discussed in the main text. To see this figure in color, go online.