Biomedical Engineering Reference
In-Depth Information
Fig. 2.2
Experimental procedures of three types of olfactory classical conditioning using PER.
(
a
) Absolute conditioning (paired conditioning). Absolute conditioning is a pairing of 4 s of an
odor (CS+:
white bars
) and subsequent 3 s of sucrose solution (US:
black squares
) with 1 s over-
lap. Here, animals receive fi ve trials of paired conditionings with intertrial interval of 10 min and
are tested with two odors, conditioned odor (CS:
white bar
) and novel odor (NO:
gray bar
),
60 min after conditioning. (
b
) Unpaired conditioning. In unpaired conditioning group, animals
receive explicitly unpaired presentations of the CS and of the US (fi ve odor-only and fi ve sucrose-
only presentations, 5 min apart in a pseudorandomized sequence) and are tested with CS (
white
bar
) and NO (
gray bar
). (
c
) Differential conditioning. During differential conditioning, one odor
is paired with sucrose (CS+:
white bars
), and the other odor is presented without sucrose (CS−:
gray bars
)
(sucrose solution, US). Here, to observe trained-odor-specifi c memory, we will use
one odor (CS1) for conditioning and two odors (CS1 and NO, 1-nonanol and
2-hexanol) in memory retention tests. Parameters such as the number of trials and
the duration of the intertrial interval (ITI) can be manipulated according to the pur-
pose of the experiment. In this text, we will describe the standard procedure of
absolute conditioning with 5 CS-US pairings with intertrial intervals of 10 min
(Fig.
2.2a
). This procedure yields a robust and stable long-term memory that can be
retrieved several days after conditioning (>4 days) and that is protein synthesis
dependent (Menzel
1999
). Learning effi ciency is highly affected by circadian
rhythm and is lowest around early evening (Lehmann et al.
2011
). Thus, condition-
ing should be planned to end before 1600 hours. Twenty bees are used in this experi-
mental procedure.
1. Place two syringes for olfactory stimulation, sucrose solution (in an Eppendorf
tube), and a toothpick on the table. If using an odor stimulation device, this
should be checked before beginning.
2. Set the fi rst honeybee (bee A) in front of the exhaust. The bee should be left to
familiarize with the experimental situation for at least 15 s before applying any
stimulation.
