![]() Neural stem cell (radial glia) shown in green Adult neurogenesis in different systems Īdult neurogenesis in the avian brain occurs in many different pallial regions, including the song nuclei, the hippocampus, and the olfactory regions. ![]() Indeed, some newborn neurons have been shown to undergo non-radial glia accommodated migration, where they do not move on the radial glia processes but rather "wander" around in a saltatory manner until they reach their destination. However, there is evidence that another form of migration is also in place. Radial glia asymmetrically divide to give rise to new neurons Neurons born in the ventricular zone first migrate tangentially along the ventricular zone, then radially on radial glia processes to their destination. Radial glia, a subset of vimentin-expressing glial cells that are the adult neural stem cells, reside in the dorsal and ventral ventricular zone and extend long processes that permeate the neural tissue. Neurogenesis occurs throughout the ventricular zone, but proliferation is especially high in specific locations in the lateral wall of the ventricle. New neurons are born on the walls of the lateral ventricles ( ventricular zone) and migrate to their destination where they integrate into the existing circuits. Historically, the discovery of adult neurogenesis in songbirds substantially contributed to establishing the presence of adult neurogenesis and to progressing a line of research tightly associated with many potential clinical applications. Methods used in research to track adult neurogenesis in birds include the use of thymidine analogues and identifying endogenous markers of neurogenesis. The increased extent of adult neurogenesis in birds compared to other vertebrates, especially in circuits that underlie complex specialized behavior, makes birds an excellent animal model to study this process and its functionality. The degree of postnatal and adult neurogenesis in songbirds varies between species, shows sexual dimorphism, fluctuates seasonally, and depends on hormone levels, cell death rates, and social environment. Adult neurogenesis in songbirds is observed in brain circuits that underlie complex specialized behavior, including the song control system and the hippocampus. Avian species including songbirds are among vertebrate species that demonstrate particularly robust adult neurogenesis throughout their telencephalon, in contrast with the more limited neurogenic potential that are observed in adult mammals after birth. Adult neurogenesis is the process in which new neurons are born and subsequently integrate into functional brain circuits after birth and into adulthood.
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