  Spatial coexistence of coherent and incoherent dynamics in network of coupled
oscillators is called a chimera state. We study such chimera states in a
network of neurons without any direct interactions but connected through
another medium of neurons, forming a multilayer structure. The upper layer is
thus made up of uncoupled neurons and the lower layer plays the role of a
medium through which the neurons in the upper layer share information among
each other. Hindmarsh-Rose neurons with square wave bursting dynamics are
considered as nodes in both layers. In addition, we also discuss the existence
of chimera states in presence of inter layer heterogeneity. The neurons in the
bottom layer are globally connected through electrical synapses, while across
the two layers chemical synapses are formed. According to our research, the
competing effects of these two types of synapses can lead to chimera states in
the upper layer of uncoupled neurons. Remarkably, we find a density-dependent
threshold for the emergence of chimera states in uncoupled neurons, similar to
the quorum sensing transition to a synchronized state. Finally, we examine the
impact of both homogeneous and heterogeneous inter-layer information
transmission delays on the observed chimera states over a wide parameter space.
