Fig. 2.

Illustration of ground truth simulation for structural trajectories. (A) 5 random realizations of an ensemble of linear trajectories are plotted over the adult lifespan. Individual trajectories are shown in blue and the average trajectory is shown in red. (B) Illustration of simulated MRI acquisition. Ages of measurement t_ij are depicted by red crosses and red lines. Balanced designs (2 and 3 from left) vs. unbalanced (4 and 5 from left) and low (2nd from left) vs. high (3rd from left) sparsity of observations. Unbalanced sampling is illustrated using the age interval [20, 70] but see text for exact specification of the simulation.