Moreover, because at least some local interneurons within the deutocerebrum receive short-latency inputs from hydrodynamic receptors on the antennular flagella in addition to long-latency inputs from the aesthetascs (Mellon, 2005), interactions between the different central response phases may depend critically upon the transmission time to the brain from the receptor neurons in the different regions of the lateral flagellum.
Type I interneurons are the largest neurons that have been characterized in the crayfish deutocerebrum (Mellon and Alones, 1995); with dendritic processes up to 20 [micro]m in diameter within the OL, they can be more readily penetrated with sharp micropipette electrodes than any other resident interneurons.
104 in a large animal, are providing optimal excitation to the neurons within the deutocerebrum, and those ORNs within aesthetascs very close to the start of the array are dramatically the most effective.
sinensis is composed of protocerebrum, deutocerebrum
, and tritocerebrum.
Thus, even higher-order processing of the two pathways remains relatively distinct, with the exception that some local interneurons in the deutocerebrum
appear to innervate both the OL and LAN (Schmidt et al., 1992; Mellon and Alones, 1995; Mellon, 1996; Schmidt and Ache, 1996b).
Crustacean ORN axons course within the antennular nerve to a specific, ipsilateral region of the deutocerebrum, the olfactory lobe (OL), characterized in all decapods (as in the immediate central nervous targets of olfactory axons in all other arthropods as well as in vertebrates) by compartmentalized aggregations of neuropil referred to as glomeruli.
Figure 1 is a simplified diagram of the crayfish deutocerebrum and some of its input and output connections.
The deutocerebrum. The deutocerebrum can be subdivided into two distinct regions, which we call the circular deutocerebral neuropils and median deutocerebral neuropils [ILLUSTRATION FOR FIGURES 3B, 4A, 5 OMITTED].
The cephalic sensory input in the cyprid can be summarized as follows: primary nerves from the median eye project to the dorsofrontal neuropil; primary nerves from each compound eye form an optic tract and project to the optic lobe; primary nerves from each frontal filament form a frontal filament tract and project also to the optic lobe; and primary nerves that innervate setae on the antennule project to the deutocerebrum.
In decapods, as in insects, this pathway is composed of two elements: bilateral glomerular neuropils of the deutocerebrum, where olfactory afferents transmit information onto local interneurons and projection neurons (antennal lobes in insects; olfactory lobes in decapods); and bilateral second-order neuropils of the protocerebrum, to which the projection neurons ascend (mushroom bodies in insects; hemiellipsoid bodies in decapods) (e.g., Boeckh et al., 1984; Blaustein et al., 1988; Mellon et al., 1992).
Significant differences between species exist in the occurrence of neurogenesis among local interneurons of the olfactory deutocerebrum and among neurons that probably represent local interneurons of the hemiellipsoid bodies.
Threshold and odor specificity of pheromone-sensitive neurons in the deutocerebrum
of Anthera pernyi and A.