Structural organization of the mormyrid electrosensory lateral line lobe

The electrosensory lateral line lobe (ELL) of mormyrid teleosts is the firs t central stage in electrosensory input processing. It is a well-developed structure with six main layers, located in the roof of the rhombencephalon, Its main layers are, from superficial to deep, the molecular, ganglionic, plexiform, granular, intermediate and deep fiber layers, An important input arises from electroreceptors, but corollary electromotor command signals a nd proprioceptive, mechanosensory lateral line and descending electrosensor y feedback inputs reach the ELL as well, The ELL input is processed by at l east 14 cell types, which frequently show plastic responses to different in puts, The large ganglionic and large fusiform cells are the ELL projection cells, They are glutamatergic and project to the isthmic preeminential nucl eus and the midbrain lateral toral nucleus. Interneurons are located in all ELL layers and are mostly GABAergic, The most remarkable internenrons are large multipolar cells in the intermediate layer, which have myelinated den drites making presynaptic terminals contacting granular cells. With respect to the synaptic organization and microcircuitry of the ELL, a number of qu alitative and quantitative aspects have been elucidated using electron micr oscopical and intracellular labeling techniques, However, the pathways by w hich primary afferent input influences the ELL projection cells are still u ndetermined: primary afferents do not seem to contact large fusiform or lar ge ganglionic cells directly, but seem to terminate exclusively on granular cells, the axonal properties of which are not known, Consequently, more in formation of the structural organization of the ELL is still necessary for a detailed understanding of the neural basis of the plastic electrosensory input processing in mormyrids.