Function-specific distribution patterns of axon terminals of input neurons in the calyces of the mushroom body of the cockroach, Periplaneta americana

Input neurons (INs) in the calyces of the mushroom bodies (MBs) of the cockroach brain were examined by single- or multiple-staining with cobalt lysine and by Golgi impregnation. Olfactory INs had axon terminals with tuft-like, button-like or spiny-blebbed arbors in specific concentric zones in calycal neuropil. INs which responded to light stimulation had thick brush-like arbors along with axonal branches extending radially along the inner layer of calycal neuropil. Some of multiglomerular INs and two types of protocerebral INs extended blebbed axonal branches to the outer surface layer of calycal neuropil or thick bush-like axonal branches with many varicosities to entire calycal neuropil. The distribution patterns of dendrites and axon terminals of INs in the calyces suggest the existence of functional subdivisions in calycal neuropil.