Interest has increased in the past decade in intrinsic functional connectivity (iFC) studies based on the resting-state fMRI. Previous iFC studies have generally focused on strong connectivity patterns (e.g., top 5% or iFC larger than 0.20), for both diagnostic purposes, and understanding of the organization and developmental trajectories of human brain. Thus, weak connections are usually considered spurious and assigned a value of zero, resulting in the fact that the role of weak connections has remained obscure for years. This is somehow surprising, given that weak connections in other complex systems had already been stressed many years ago, including the social networks. However, little is known about the functional significance of weak iFC in human brain. Here we addressed this question by directly testing the behavioral significance of the weak iFC between the core structures of two relatively independent systems for spatial navigation (i.e., hippocampus and caudate).