Local circuitry in the anterior caudal lobe of the mormyrid cerebellum: A study of intracellular recording and labeling

Abstract

The caudal lobe of the mormyrid cerebellum includes the anterior portion, which is associated with the lateral line and eighth nerve senses, and the posterior portion, which is associated with the electrosense. This study examines the physiology and morphology of cells in the anterior portion in slice preparations. Two subtypes of Purkinje cells, efferent cells and stellate cells, are described. Multipolar Purkinje cells are located in the central region of the lobe, with large, multipolar, spiny dendrites and locally ending axons. Small Purkinje cells are located along its anterior border with the eminentia granularis anterior (EGa), with spiny dendrites in the molecular region. Axons of some small Purkinje cells end locally, whereas axons of other such cells are cut at the surface of the slices, suggesting that they project outside the lobe. Efferent cells are also distributed along the border with EGa. These cells have thin, smooth dendrites in the molecular region, and their axons are cut at the sliced surface. Stellate cells have thin, smooth dendrites and locally terminating axons. Physiologically, all types of cells respond to parallel fiber activation, but only multipolar Purkinje cells showed characteristic all-or-none climbing fiber responses. Although the majority of Purkinje cells fire a single type of spikes at resting level, a subset of small Purkinje cells fire small, narrow and large, broad spikes. Thus, the anterior caudal lobe of the mormyrid cerebellum is different from the mammalian cerebellum in having different subtypes of Purkinje cells and local termination of many Purkinje cell axons.

Cell type-specific plasticity at parallel fiber synapses onto Purkinje cells in the posterior caudal lobe of the mormyrid fish cerebellum

“…Our previous work also showed that in an fPC, the regions occupied by PFs and the single CF are clearly separated spatially (Han et al 2006), and that this is also the case for mPCs (Zhang et al 2008), Such a separation of inputs facilitates their selective activation, and we have shown this to be true for both PC subtypes (Fig. 2, A 2 and B 2 ).…”

“…The large multipolar cells have been classified as PCs on the basis of their morphology and connectivity (Bell and Szabo 1986;Campbell et al 2007). As shown in our previous work, PF and CF synapses onto mPCs are spatially segregated (Zhang et al 2008), with CF terminals apposed to the soma and proximal dendritic regions, and PFs making synaptic contacts largely in the distal dendrites. By careful positioning and repositioning of the stimulation electrodes, PFs and an mPC's single CF can be selectively activated, as shown in Fig.…”

“…An anatomical study has shown that similar sagittal strips, as defined by the distributions of CFs and efferent cells, are present in the central lobes of the mormyrid cerebellum (Han et al 2006). However, this structure is completely lacking in the molecular zone of the caudal lobes (Campbell et al 2007;Zhang and Han 2007;Zhang et al 2008), where the mormyrid's mPCs are located (Bell and Szabo 1986). This contrasts with the mammalian cerebellum, where a modular organization is generally considered a uniform pattern (Apps and Hawkes 2009;Ruigrok 2011) and PCs are absent from the molecular layer.…”

Effects of local anesthesia of the cerebellum on classical fear conditioning in goldfish

“…Histological and physiological studies have suggested that the cerebellar inputs and outputs in teleost fish are similar to those in mammals [21,22]. Furthermore, intrinsic cerebellar circuitry in teleost fish shares basic features with that in mammals [19,20].…”

“…However, the role of the cerebellum in emotional learning in teleost fish is poorly understood, whereas the cerebellum obviously shares major intrinsic circuitry, as well as afferent and efferent connections with other brain parts, with those in the mammalian cerebellum [19-22]. …”