Pyramidal cell modules

Pyramidal Cell Modules Anatomically Defined Units Based on Apical Dendrite Clustering... 

Fig. 3 Diagrammatic representation of the pyramidal cell module in rat primary visual cortex, area 17. The cortical layers are indicated on the left and the number of neurons in each layer contributing to the module is given on the right. After Peters (1993)...

In addition to vertical bundles of myelinated axons, the cerebral cortex of monkeys (e.g., DeFelipe et al., 1990) and of humans (e.g., del Rio and DeFelipe, 1995) also contains vertically oriented bundles of unmyelinated axons that are referred to as horsetails. These horsetails are the axonal plexuses of the inhibitory double bouquet cells and can be demonstrated in monkey neocortex by immunolabeling with antibodies to calbindin and tachykinin. As shown by DeFelipe et al. (1990), in the monkey these axonal bundles are widespread and form a regular columnar system descending from layer 2 to layers 3-5. The bundles are most evident in tangential sections taken at the level of layer 3, where they can be seen to have a center-to-center spacing of 15-30 fim. In a later study of the calbindin labeled double bouquet cells in monkey striate cortex, Peters and Sethares (1997) showed that there is one double bouquet cell, and therefore one vertically oriented double bouquet cell axonal plexus, or horsetail, per pyramidal cell module (Fig. 7). Within layer 2/3 the double bouquet axons run alongside the apical dendritic clusters, while in layer 4C they are closely associated with the vertical myelinated axonal bundles. DeFelipe et al. (1989 1990) proposed that the axon terminals of the double bouquet cell synapse with the shafts and spines of basal dendrites and oblique shafts of apical dendrites of pyramidal cells, but the exact role of these vertical bundles of inhibitory axons is not known. It is likely that they constitute a vertical inhibitory system that acts upon pyramidal cells within the minicolumns. 

Fig. 7 Diagram of the microcolumn in monkey visual cortex to show that there is one double bouquet cell horsetail black) per pyramidal cell module. The other colors correspond to those in Fig. 5, which explains the composition of the pyramidal cell modules in monkey area 17. From Peters and Sethares (1997)...

One reason why more studies like that of Gabbott (2003) have not been carried out is that most studies of the composition and dimensions of dendritic clusters and pyramidal cell modules have been carried out in mice, rats, cats, and rabbits, with a few studies in monkeys and only one in humans (see Table 1). In contrast all of the studies of the dimensions of minicolumns based on spacing of vertical strings of neurons in Nissl stained sections have been carried out in monkeys, ape, and human cortex (see Table 2). 

Lohmann H, Kbppen HJ (1995) Postnatal development of pyramidal cell modules and axonal bundles in the visual cortex of the rat. J Hirnforsch 36 101-111. 

Peters A (1993) Pyramidal cell modules in rat visual cortex. In Eormation and regeneration of nerve connections. (Sharma SC, Eawcett JW eds.), pp. 102-119. Birkhauser Boston... 

Peters A, Sethares C (1996) Myelinated axons and the pyramidal cell modules in monkey primary visual cortex. J Comp Neurol 365 232-255. 

Seidenman K. J., Steinberg J. P., Huganir R., and Malinow R. (2003). Glutamate receptor subunit 2 Serine 880 phosphorylation modulates synaptic transmission and mediates plasticity in CA1 pyramidal cells. J. Neurosci. 23 9220-9228. 

Rozov A, Burnashev N, Sakmann B, Neher E (2001) Transmitter release modulation by intracellular Ca2+ buffers in facilitating and depressing nerve terminals of pyramidal cells in layer 2/3 of the rat neocortex indicates a target cell-specific difference in presynaptic calcium dynamics. J Physiol 531 807-26... 

Jarolimek W, Misgeld U (1997) GABAB receptor-mediated inhibition of tetrodotoxin-resistant GABA release in rodent hippocampal CA1 pyramidal cells. J Neurosci 17 1025-32 Jeong SW, Ikeda SR (2000a) Effect of G protein heterotrimer composition on coupling of neurotransmitter receptors to N-type Ca(2+) channel modulation in sympathetic neurons. Proc Natl Acad Sci USA 97 907-12... 

Krueger BK, Font J, Greengard P (1977) Depolarization-induced phosphorylation of specific proteins, mediated by calcium ion influx, in rat brain synaptosomes. J Biol Chem 252 2764-73 Kubista H, Boehm S (2006) Molecular mechanisms underlying the modulation of exocytotic noradrenaline release via presynaptic receptors. Pharmacol Ther 112 213 12 Kulik A, Vida I, Fukazawa Y et al (2006) Compartment-dependent colocalization of Kir3.2-containing K+ channels and GABAB receptors in hippocampal pyramidal cells. J Neurosci 26 4289-97... 

Nigella sativa Linn. Nigella sativa Linn, seed (NS) has positive modulation effects on memory impairments, prevents hippocampal pyramidal cell loss, and enhances consolidation of recall capability of stored information and spatial memory [283],... 

FG-Loop (FGL), a neural cell adhesion molecule-derived peptide that corresponds to its second fibronectin type III module, has been shown to provide neuroprotection against a range of cellular insults. FGL improves memory and alleviates the deleterious effects on CA1 pyramidal cells induced by AP25-35 injection. These effects might be due to inactivation of GSK3P [597]. 

Fig. 5 Diagram to show the differences in the arrangement of pyramidal neurons in areas 17 and 18 of monkey visual cortex. Not aU of the neurons in a module are shown in the diagram. The pyramidal cells in layers 5, 4A, 3, and 2 are shown in red, and the pyramidal cells in layer 6A are in green. Neurons in layer 4 are grey, while inhibitory neurons are orange. The bundles of myelinated nerve fibers that extend from the modules to enter the white matter are shown in blue.

It is evident that the modules of pyramidal cells whose apical dendrites form clusters and the vertical bundles of myelinated axons are facets of the same basic, modular organization of neurons into vertical units that we can refer to as minicolumns. And... 

Fig. 13. Basic olfactory network. Schematic of the networks linking the olfactory bulb and primary olfactory cortex. Olfactory nerve axons (ON) terminate in the glomeruli (glom) onto mitral (m) and tufted (t) cells which project via the lateral olfactory tract (LOT) to layer la of primary olfactory cortex to terminate on the dendrites of layer Il-III pyramidal (p) cells. Layer 11-111 pyramidal cells in rostral olfactory cortex project to layer Ib in caudal olfactory cortex and vice versa. Olfactory cortical pyramidal cells also send reciprocal projections back to the olfactory bulb. Thus olfactory bulb output is continuously modified by feedback from areas it targets. Inhibitory interneurons in olfactory bulb and olfactory cortex (shown in gray) modulate network function. Neurons in the ipsilateral (AONi) and contralateral anterior olfactory nuclei (AON) link olfactory networks in the two hemispheres via the anterior commissure.

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