Biomedical Engineering Reference
In-Depth Information
At the end of training, the odor alone elicits the PER, indicating that the bee has
learnt the odor-reward association (Takeda
1961
; Bitterman et al.
1983
). The PER
is usually recorded as a dichotomous response (1 or 0), which can thus be used as a
precise index for learning and memory performance.
Olfactory conditioning of the PER is performed at an individual level, on
immobilized honeybees placed in small harness tubes. This allows simultaneous
or consecutive monitoring of behavior and neuronal activity, for instance, using
neurophysiological or optophysiological techniques, during memory acquisition
and memory retrieval (e.g., Faber et al.
1999
; Okada et al.
2007
; Strube-Bloss
et al.
2011
). In this chapter, we detail a simple protocol for absolute classical con-
ditioning of the PER which can be established with minimal investment in any
laboratory.
2.2
Preparation for the Experiment
2.2.1
Materials
Honeybees, 20 harness tubes, tube rack, ice water, 30 mL glass screw vial (make
small vent holes on the cap to avoid suffocation), 50 % (weight/weight) sucrose
solution (1.80 M), toothpick, odorants, fi lter papers, 20 mL syringes, and latex
examination gloves.
2.2.2
Honeybees
When adult worker bees age, their tasks shift from nursing to guarding and then to
foraging (von Frisch
1967
; Seeley
1982
,
1995
). Foragers, the older bees that go out
of the hive to collect food, are reported to have the highest learning ability among
bees working on other tasks (nurse, guardian) (Ray and Ferneyhough
1999
). This
makes sense as the subjective value of sucrose reward is probably higher in animals
whose foraging motivation is also higher. This is why a control of the kind of bees
used in olfactory PER conditioning experiments is desirable. Confounding several
casts of bees in the same set of data will mask specifi c learning abilities and pool
together animals that differ dramatically in their unconditioned response to sucrose
reward (Scheiner et al.
2001
). Generally, foragers are captured while leaving the
hive and used for experiments (e.g., Guerrieri et al.
2005a
). In other cases, emerging
bees are placed in cages in an incubator and maintained in controlled conditions
until reaching foraging age (Pham-Delègue et al.
1993
). Even more recommend-
able, in order to ensure the presence of foragers in the bees to be conditioned, is the
previous training to an ad libitum sucrose feeder placed close to the hive on which
regular foragers will be collected for experiments.
