Figure 4.

Ratio of sulcal depth at P14 and P21 relative to P28. Points residing in the 6 major sulci of the ferret were identified via an applied threshold of sulcal depth values at P28. The ratio of sulcal depth at P14 and P21 relative to P28 represents the progress in folding toward maturation. As relative distance from the origin of the TNG increase, the sulcal depth ratio from P14 to P28 decreases (slope = −0.14; intercept = 0.55) while the ratio from P21 to P28 decreases at a much lower rate (slope = −0.03; intercept = 0.82).