  We study various relay synchronization scenarios in a three-layer network,
where the middle (relay) layer is a single node, i.e. a hub, The two remote
layers consist of non-locally coupled rings of FitzHugh-Nagumo oscillators
modelling neuronal dynamics. All nodes of the remote layers are connected to
the hub. The role of the hub and its importance for the existence of chimera
states is investigated in dependence on the inter-layer coupling strength and
inter-layer time delay. Tongue-like regions in the parameter plane exhibiting
double chimeras, i.e., chimera states in the remote layers whose coherent cores
are synchronized with each other, and salt-and-pepper states are found. At very
low intra-layer coupling strength, when chimera states do not exist in single
layers, these may be induced by the hub. Also the influence of dilution of
links between the remote layers and the hub upon the dynamics is investigated.
The greatest effect of dilution is observed when links to the coherent domain
of the chimeras are removed.
