New research by the University of Southern California seems to confirm the non-hierarchical model of brain organization.
In the past it was common to believe that the brain was organized hierarchically, this preconception was challenged by the network hypothesis, which has been gradually growing in popularity. However neither model had much empirical support so far.
Now Richard H. Thompson and Larry W. Swanson have found that, at least for a particular region of the brain of rats, the reality is non-hierarchical but that of a complex network.
Richard H. Thompson and Larry W. Swanson, Hypothesis-driven structural connectivity analysis supports network over hierarchical model of brain architecture. PNAS 2010. Pay per view (depending on geography and time of access).
Press articles at Science Daily and BBC.