FUNCTIONAL-ORGANIZATION OF OLFACTORY PROCESSING IN THE ACCESSORY LOBEOF THE SPINY LOBSTER

An isolated brain preparation was used to characterize neurons innerva ting the accessory lobe (AL) of the spiny lobster (Panulirus argus). F our distinct classes of neurons responded to electrical stimulation of the olfactory (antennular) nerve. These cells responded to electrical stimulation with a long and variable latency; they also responded to odor stimulation in a nose-brain preparation. Neurons connecting the A L with the olfactory lobe branched in the central AL layer and selecti vely innervated olfactory lobe glomeruli. These cells had response lat encies which were significantly shorter than those of other AL neurons . Intrinsic AL interneurons were heterogeneous as a population, and mo st arborized in irregular but circumscribed regions of either the late ral or medial layers. The final class of neurons branched ipsilaterall y in the deutocerebral neuropil and bilaterally innervated only a few AL glomeruli. The physiology and morphology of these four classes of n eurons confirm an olfactory function for the AL and identify the input and output regions of the lobe. Based on these findings, we propose t hat the AL processes odor information in the context of higher order m ultimodal input.