  Directed information transmission is paramount for many social, physical, and
biological systems. For neural systems, scientists have studied this problem
under the paradigm of feedforward networks for decades. In most models of
feedforward networks, activity is exclusively driven by excitatory neurons and
the wiring patterns between them, while inhibitory neurons play only a
stabilizing role for the network dynamics. Motivated by recent experimental
discoveries of hippocampal circuitry, cortical circuitry, and the diversity of
inhibitory neurons throughout the brain, here we illustrate that one can
construct such networks even if the connectivity between the excitatory units
in the system remains random. This is achieved by endowing inhibitory nodes
with a more active role in the network. Our findings demonstrate that apparent
feedforward activity can be caused by a much broader network-architectural
basis than often assumed.
