  Databases of directed- and weighted- connectivity for mouse, macaque and
marmoset monkeys, have recently become available and begun to be used to build
dynamical models. A hierarchical organization can be defined based on laminar
patterns of cortical connections, possibly improved by thalamocortical
projections. A large-scale model of the macaque cortex endowed with a laminar
structure accounts for layer-dependent and frequency-modulated interplays
between bottom-up and top-down processes. Signal propagation in a version of
the model with spiking neurons displays a threshold of stimulus amplitude for
the activity to gain access to the prefrontal cortex, reminiscent of the
ignition phenomenon associated with conscious perception. These two examples
illustrate how connectomics may inform theory leading to discoveries.
Computational modeling raises open questions for future empirical research, in
a back-and-forth collaboration of experimentalists and theorists.
