CRAYFISH BRAIN INTERNEURONS THAT CONVERGE WITH SEROTONIN GIANT-CELLS IN ACCESSORY LOBE GLOMERULI

Freshwater crayfish have well-developed olfactory systems with an arra y of receptors that project exclusively to areas in the brain that are functionally specialized for the processing of odors. The accessory l obes are large bilateral areas of neuropil that are anatomically assoc iated with the olfactory lobes. The accessory lobes receive no primary afferents and do not contain the endings of motor efferents; thus, th eir role in olfaction is still obscure. Intracellular dye filling of i nterneurons in the deutocerebral commissure in the crayfish brain has shown that they end bilaterally in glomeruli in the accessory lobes, h ave cell somata in a dorsal cluster medial to the olfactory lobes, and have unilateral projections to the deutocerebral commissure neuropil. Each deutocerebral commissure interneuron has only 6 to 15 output glo meruli in each accessory lobe and does not share glomeruli with other deutocerebral commissure interneurons. The deutocerebral commissure in terneurons converge with the dorsal giant serotonin neurons in the acc essory lobe glomeruli. Deutocerebral commissure interneurons can be se parated into classes according to their projections to the protocerebr um, central body, and deutocerebrum. Physiological responses of the de utocerebral commissure interneurons following photic stimulation of th e eyes and electrical stimulation of the second antennae lead to the c onclusion that the deutocerebral commissure represents an input to the accessory lobes from the protocerebral neuropils and that visual and tactile inputs are included in the processing performed in the accesso ry lobes. (C) 1995 Wiley-Liss, Inc.