  In the standard seesaw model, finite corrections to the neutrino mass matrix
arise from one-loop self-energy diagrams mediated by a heavy neutrino. We
discuss the impact that these corrections may have on the different low-energy
neutrino observables paying special attention to their dependence with the
seesaw model parameters. It is shown that sizable deviations from the
tri-bimaximal mixing pattern can be obtained when these corrections are taken
into account.
