In mammals, the connection between odor and the brain occurs over a single nerve connection. The olfactory sensory neurons (OSNs) that have the same odorant receptor (OR) are directed to regions of the olfactory bulb, where they coalesce into a single structure, a glomerulus. This process is molecularly determined, but it remains controversial to what extent the process also relies on stimulation from the outside.
The visual system, it is known, develops initially without any functional activity, but is later refined and polished through sensory activity. Charles Greer, professor of neurosurgery at Yale, and his collaborators. examined the postnatal formation of glomeruli in odor receptors M71 and M72 in gene-targeted mice during development to determine whether the same development process is found in the olfactory system.
The results of the study established four principles of olfactory system development -- without sensory activity there is no full maturation; there is a sensitive period during which activity influences the maturation of the organization; sensitive periods occur at different times for different olfactory receptors; and glomeruli may be innervated by more than one kind of sensory nerve during early development.
The lead author on the paper was Dong-Jing Zou of Columbia. Co-authors included Paul Feinstein and Peter Mombaerts of Rockefeller University; Aimee Rivers, Glennis Matthews, Ann Kim and Stuart Feinstein, from Columbia.
Citation: Science, (Sciencexpress): pp 1-10 (June 3, 2004)
Journal
Science