Olfaction is vitally important to animals in all environments and is used to identify
food, habitat, conspecifics and predators. Some odors, like pheromones or the pungent
smell of spoiled foods, can trigger pre-existing behavioral responses that appear to
require no learning. Most odors, however, are only attended to as a result of prior
experience. It is believed that different types of odors are processed in different olfactory
pathways in the forebrain. This thesis examines the relationship between innate and
learned olfactory behaviors and the anatomy of the neural pathways that underlie them,
using the zebrafish olfactory system as a model.
I first characterized an appetitive olfactory behavior, which is displayed promptly
by zebrafish when they encounter amino acid odors. A similar appetitive behavior can
also be learned by the fish for another, initially neutral odorant, if it is repeatedly paired
with food rewards. Zebrafish can therefore respond to, and learn to respond to certain
odors. I then conducted an in-depth anatomical analysis of the structure and distribution
of glomeruli in the zebrafish olfactory system. Glomeruli are spheroidal synaptic
aggregates that organize and shape olfactory information that arrives in the brain.
Throughout the development of zebrafish, I identified two distinct populations of
glomeruli. One population consisted of 25 individually identifiable, anatomically
stereotypic glomeruli that closely resembled specialized glomeruli in mammals and
insects. These glomeruli were already formed during embryonic development and
persisted in remarkably stable configurations throughout later developmental stages. I
hypothesize that the 25 individually identifiable glomeruli constitute stable olfactory
pathways (i.e., for innate olfactory behaviors). Most glomeruli, however, were
anatomically variable and displayed different distributions within coarsely circumscribed
regions in the zebrafish olfactory bulbs. The development of these glomeruli could be
modified by sensory experience, suggesting that they may comprise plastic olfactory
pathways that subserve the establishment of learned olfactory behaviors. Collectively my
results show that innate and learned olfactory behaviors may indeed be represented in
different olfactory pathways, and that these types of pathways may be located in both
main and accessory olfactory systems.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/13342 |
| Date | 10 March 2011 |
| Creators | Braubach, Oliver Robert |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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