Figure 1.

(a) Mathematical model Ax = b, where x describes the mechanism that relates brain activity to phenotype (psychiatric assessments). The contrast map for a single subject, a_k, provides the kth row of A. As there are still many unknown biological variables, the problem is underdetermined and x cannot be found uniquely; instead we must settle for a probable result such as a maximum likelihood solution which utilizes prior knowledge, or an estimable component of x. (b) Continuum between rowspace components and most probable solution, based on increasing confidence in the prior knowledge, which we control by the relaxation parameter δ₁.