Neurons In Turn Research Articles

In vivo and in vitro development of serotonergic neurons

The monoamines are one of the earliest developing neurotransmitter systems in the mammalian brain. The first part of this paper describes the normal ontogeny of the serotonergic (5-HT) system in the rat brain as studied using long survival 3H-thymidine autoradiography (time of neuronal genesis, time of origin) and the Falck-Hillarp histofluorescence method, electron microscopy, and immunocytochemistry (anti-5-HT). Due to their early ontogeny relative to other brain regions, 5-HT neurons (as well as monoamine neurons in general) have been suggested to exert some type of “trophic” influence on brain development. Results of pharmacological experiments designed to inhibit 5-HT synthesis in the embryonic rat brain by maternal treatment with p-chlorophenylalanine (pCPA) at a time when this monoamine might exert such an influence are discussed with regard to effects on the time course of neuronal genesis (time of origin) of 5-HT neurons and their target cells. These results, which prompted us to propose that 5-HT might act as a “differentiation signal” for certain of its target cells, are now discussed in light of our more recent immunocytochemical-autoradiographic studies (anti-5-HT, 3H-thymidine) which morphologically demonstrate close associations between developing 5-HT neurons and proliferating neuroepithelial cells in the embryonic brain. Postnatal studies using this immunocytochemical-autoradiographic method also provide evidence for interactions of 5-HT axons with proliferating glioblasts in the developing cerebellum and with immature granule cells and their precursors in the hippocampus. These findings, in conjunction with the results of our pCPA experiments, further enhance the possibility that 5-HT neurons could exert an epigenetic influence on the development of less differentiated cells with which they come into contact. Finally, preliminary studies using dissociated cell cultures containing 5-HT neurons suggest that interactions between 5-HT neurons and glial elements may be important for the differentiation of these neurons in vitro. Whether 5-HT neurons in turn influence the development of glial or neuronal cells in these cultures remains to be determined. These studies are evaluated with regard to a possible pre-transmission role for 5-HT during key phases of neuronal and glial genesis.

A Novel Firing Rule For Training Kohonen SelforganisingMaps

Statistical Process Control Charts can exhibit six principal types of patterns: Normal, Cyclic, Increasing Trend, Decreasing Trend, Upward Shift and Downward Shift. All except Normal patterns indicate abnormalities in the process that must be corrected. Accurate and speedy detection of such patterns is important to achieving tight control of the process and ensuring good product quality. This paper describes an implementation of the Kohonen self-organising map which employs the Euclidean Distance as the firing rule for control chart pattern recognition. First, the structure of the network is outlined and the equations which govern its dynamics are given. Then the learning mechanism of the network is explained. The effects of different combinations of network parameters on classificatio n accuracy are discussed. A novel firing rule for the Kohonen self-organising map is proposed. This rule involves component-bycomponent comparison between the input pattern and the established class templates. When an input vector is presented, it is compared with the class templates in all the neurons in turn. The neuron containing the class template that best matches the input vector will subsequently fire. This approach is intended to enhance the generalisation capability and accuracy of the Kohonen selforganising map. The paper gives a comparison of the results obtained using the Euclidean Distance and the proposed firing rule.