smells

So why is it that when you smell certain things it brings back a memory.
I can smell this certain smell and it brings back memories a christmas
morning like 20 or 21 years ago. I can't describe this smell, but it is
very specific and I know when I smell it. I was driving to work this
morning and there it was, this smell, and all of a sudden I thought of
Christmas when I was like 4. Well if you are wondering why this happens,
here's the reason. Although I'm sure it's more scientific than most of
you would like...sorry!

Inside your nose about the level of your eyes, is a small patch of
tissue containing millions of nerve cells. The odor receptors (sensors)
lie on these nerve cells. Each of the receptors recognizes several
odors, and likewise a single odor could be recognized by several
receptors. So, similar to codes, what happens is that different
combinations of the 1,000 receptors result in our ability to identify
10,000 different odors. The process that takes place is pretty complex.
After an odor molecule enters the nose and are recognized by the
olfactory sensors, the signals are eventually sent to the olfactory bulb
that is located right above the eyes. The signals only go to two areas
in the olfactory bulb, and signals from different sensors are targeted
to different spots that then form a sensory map. From there the signals
reach the olfactory area of the cortex (smell sensory cortex). An
important quality of the olfactory system is that information travels
both to the limbic system and cortex. The limbic system is the primitive
part of the brain that include areas that control emotions, memory and
behavior. In comparison the cortex is the outer part of the brain that
has to do with conscious thought. In addition to these two areas,
information also travels to the taste sensory cortex to create the sense
of flavor. Because olfactory information goes to both the primitive and
complex part of the brain it effects our actions in more ways than we
think.
Many people wonder how certain smells able to trigger memories of
events taking place several years ago despite the fact that sensory
neurons in the epithelium survive for about only 60 days. The answer is
that the neurons in the epithelium actually have successors. As the
olfactory neurons die, new olfactory neurons generated by the layer of
stem cells beneath them, which eventually takes the role of the old
neuron as it dies. The key point to the answer is that "memories survive
because the axons of neurons that express the same receptor always go to
the same place". The memories are stored in the hippocampus, and through
relational memory certain smells trigger memories.

Well, I hope you didn't fall asleep reading that...I know what you're
thining, your a NERD. And to that I say, I've told you I was a science
nerd before. Live with it.