  We consider two coupled populations of leaky integrate-and-fire neurons.
Depending on the coupling strength, mean fields generated by these populations
can have incommensurate frequencies, or become frequency locked. In the
observed 2:1 locking state of the mean fields, individual neurons in one
population are asynchronous with the mean fields, while in another populations
they have the same frequency as the mean field. These synchronous neurons form
a chimera state, where part of them build a fully synchronized cluster, while
other remain scattered. We explain this chimera as a marginal one, caused by a
self-organized neutral dynamics of the effective circle map.
