(a) Head of a mouse showing the location of the brain and the rostral migratory stream, RMS (in red), along which newly generated neuroblasts migrate from the SVZ of the lateral ventricle into the olfactory bulb (OB). (b) The migration of newly generated neuroblasts begins at the lateral ventricle, continues along the RMS and terminates in the OB, where mature interneuron populations are generated. (c) Schematic based on electron microscopy showing the cytoarchitecture of the SVZ along the ventricle. Ependymal cells (gray) form a monolayer along the ventricle with astrocytes (green), neuroblasts (red) and transitory amplifying neuronal precursors (TAP) (purple) comprising the SVZ. (d) Schematic showing the migration of neuroblasts along the RMS. Astrocytes (green) ensheath the migrating neuroblasts (red) and are thought to restrict and contain the neuroblasts to their specific pathway. (e) Migrating neuroblasts enter the OB, migrate radially and give rise to granule or periglomerular cells. From a paper by Jessica B Lennington, et al., 2003.[1]
The rostral migratory stream (RMS) is a specialized migratory route found in the brain of some animals along which neuronal precursors that originated in the subventricular zone (SVZ) of the brain migrate to reach the main olfactory bulb (OB). The importance of the RMS lies in its ability to refine and even change an animal's sensitivity to smells, which explains its importance and larger size in the rodent brain as compared to the human brain, as our olfactory sense is not as developed.[2] This pathway has been studied in the rodent, rabbit, and both the squirrel monkey and rhesus monkey.[3] When the neurons reach the OB they differentiate into GABAergicinterneurons as they are integrated into either the granule cell layer or periglomerular layer.
Although it was originally believed that neurons could not regenerate in the adult brain, neurogenesis has been shown to occur in mammalian brains, including those of primates. However, neurogenesis is limited to the hippocampus and SVZ, and the RMS is one mechanism neurons use to relocate from these areas.[4]
^Curtis, Maurice; Faull, Richard; Eriksson, Peter (2007). "The effect of neurodegenerative disease on the subventricular zone". Nature Reviews Neuroscience. 8 (9): 712–723. doi:10.1038/nrn2216. PMID17704813. S2CID12084086.
^Kam, Monica; Curtis, Maurice; McGlashan, Susan; Connor, Bronwen (2009). "The cellular composition and morphological organization of the rostral migratory stream in the adult human brain". Journal of Chemical Neuroanatomy. 37 (3): 196–205. doi:10.1016/j.jchemneu.2008.12.009. PMID19159677. S2CID9098496.