Figure 2

Toy brain test problem. Top: true connectivity map \(W_{\mathrm{true}}\) (left) and the low-rank solution with \(\mathrm{rank}=40\) and \(\lambda =100\) (right). Bottom: solutions with \(\varOmega =1\) (left) and \(\lambda =0\) (right). The locations of simulated injections are shown by the gray bars. This shows that both the mask (Ω) and the smoothing (\(\lambda > 0\)) are necessary for good recovery