"We’d like to understand how a rat makes a decision.
A decision, in this case, involves a sensory cue, an odor, and a
meaning for that odor that the rat has learned because we’ve
trained it in a particular way.
happens somewhere in the brain, where sensory information comes
together with memory, with learning, and with motivation. In this
case, the rat is motivated to find water. So it's learned
a particular cue.
rat has a very keen sense of smell. Rats can discriminate between
any pair of chemicals. There are actually many things that you or
I couldn’t distinguish that a rat has no problem learning
to tell apart.
"They use odors
in their social lives, as sources of food or to avoid predators,
and to navigate. They’re very attuned to smell versus vision
or hearing. We take advantage of that in our experiments by using
odors to direct their behavior."Essentially,
we will teach the rat that this particular odor means it will get
water as a reward. An odor can serve as a cue for the rat to tell
it where to go and at what time.
"These electrodes are very thin wires. It’s relatively
noninvasive. The rat will recover from the surgery and go back into
this behavioral chamber. We’ll record, for example, from the
neurons in the part of the brain that receives olfactory information,
the olfactory bulb, or parts of the brain that are further along
the line toward the execution of a movement, for example.
a compromise between what you can do ethically in an organism, and
the organism being close to humans. You cannot ask someone to open
up their head and examine it with electrophysiological tools that
do certain kinds of invasive imaging when it’s possible to
do it in a simpler organism. So we get a level of analysis that
is only possible in humans very rarely, such as the case of a patient
having surgery for epilepsy, for example. In humans, we get a much
coarser view of the brain."
—Zach Mainen, neuroscientist at Cold Spring Harbor Laboratory