MODULAR STRUCTURES IN THE MUSHROOM BODY OF THE COCKROACH

The mushroom body (MB) is a higher center of the insect brain and is c ritical to olfactory and other forms of associative memory. Here, we r eport that repetitive modular subunits, which we refer to as slabs, ar e present in the internal matrix of the alpha lobe, a major output neu ropil of the MB in the cockroach. The methods employed were osmium-eth yl gallate, Bodian-reduced silver, and Golgi staining procedures. A to tal of 15 dark and 15 pale slabs, each consisting of specific subsets of intrinsic neurons (Kenyon cells), alternate throughout the length o f the alpha lobe. One of the major classes of MB output neurons, which are postsynaptic to Kenyon cells, exhibited segmented dendritic arbor s that interact with every other slabs, i.e. only either dark or pale slabs. As each output neuron interacts with each specific set of dark or pale slabs, the slab likely functions as a unit for transmitting MB output signals. (C) 1997 Elsevier Science Ireland Ltd.