Biomedical Engineering Reference
In-Depth Information
Fig. 2.1
Proboscis extension
refl ex (PER) in harnessed
honeybee. Contact of the
antennae and/or proboscis
with sucrose solution elicits
the PER. Honeybees are
conditioned to extend their
proboscis in response to an
odor (CS) when the odor is
presented contingent upon a
sucrose stimulus (US)
2.3.2
Feeding Bees
Depending on the interval between capture and the start of the conditioning, it can
be necessary to feed the bees with 50 % sucrose solution: if bees were caught in the
morning of the experimental day and conditioning starts after 3-4 h, then feeding is
unnecessary; if, however, conditioning starts in the afternoon, feed a drop (~5
L)
of sucrose solution approximately 30 min after fi xation to avoid excessive starvation
and resulting mortality before start of the experiment; lastly, if bees were caught on
the day before the experiment, they should be fed to satiation and kept in a dark,
humid container at room temperature (20-25 °C) overnight. It should be kept in
mind that these are general rules of thumb, which should be adapted depending on
the season, local conditions, etc. Feeding will reduce appetitive motivation and thus
unconditioned responses (PER) to sucrose. Therefore, a good balance should be
kept between starvation and feeding, to keep bees with good appetitive motivation
and suffi cient vitality.
Use a toothpick to present sucrose solution to a bee or a micropipette with
automatized volume delivery if you want to control this factor. When sucrose solu-
tion touches the antennae, a hungry bee will elicit PER (Fig.
2.1
). Let the bee lick
the solution by touching the proboscis with the toothpick. Bees that do not show
PER are either satiated or in poor physical condition. Such bees should be removed
from the experiment due to the lack of unconditioned responses.
μ
2.3.3
Absolute Conditioning
As mentioned above, absolute conditioning is the simplest form of associative con-
ditioning (paired conditioning), in which a single stimulus (odor, CS) is reinforced
