Model connectivity.

<p>A. Synaptic schematic: Each glomerulus (dotted ellipse) receives input from olfactory receptor neurons (ORNs) expressing a single type of receptor out of many (different colors). Mitral/tufted (M/T) cells take excitatory input onto their dendritic tufts within one glomerulus, directly from ORNs (and via ET cells). ET cells have not been modeled (crossed out) and their input to M/T and PG cells is considered folded into the ORN input. Periglomerular (PG) cells are excited by ORNs (and via ET cells), and in turn inhibit M/T cells within the same glomerulus, thus causing feed-forward inhibition. PG cells also get excitation from M/T cells at reciprocal synapses, thus mediating recurrent inhibition. Further, M/T cells form reciprocal synapses with granule cells on their soma, primary and lateral dendrites, where they excite granule (G) cells which cause recurrent and lateral inhibition. Short-axon (SA) cells have not been modeled (crossed out). B. Visualization of <i>default</i> model having 3 glomeruli each with 2 sister mitral cells, and connecting interneurons. Singly connected granule cells are shown in purple. The jointly and multiply connected (shared) granule cells are shown in yellow and cyan respectively. PG cells are shown in orange. Synaptic connections are not shown, but granule and PG cells connect to nearby mitral dendrites, within their small dendritic extents.