Biomedical Engineering Reference
In-Depth Information
3. Deliver the CS and the US in an appropriate temporal relationship. Standard
stimulation consists of a pairing of 4 s of odor (CS1) and subsequent 3 s of
sucrose solution (US) with an interstimulus interval of 3 s (1 s overlap). Record
the presence (+) or absence (−) of PER in the 3 s between odor onset and sucrose
delivery (conditioned response to the odor). If the bee responds with a PER to the
odor, touch the proboscis with sucrose solution and let the bee drink for 3 s. If it
did not show PER to the odor, touch the antennae with the toothpick fi rst to elicit
PER and present sucrose solution to the bee's extended proboscis with the tooth-
pick. Let the bee drink for 3 s.
4. Leave the bee in the conditioning place for 10 s after the CS-US pairing. This is
important for the contextual cues around the setup to lose an anticipating, predic-
tive link to the US. Place the next subject (bee B), and start (2-4) again.
5. Perform the fi rst conditioning trial in all 20 subjects, recording each time PER
and sucrose solution intake, by repeating (2-4) (fi rst-trial conditioning).
6. Repeat (2-4) four more times (fi ve trials per bee in total) with an ITI of 10 min.
If you use 20 bees and exchange the subject every 30 s, which corresponds to the
duration of a conditioning trial, the second trial of the fi rst bee (bee A) will just
follow the fi rst trial of the 20th bee (bee T), and the ITI between fi rst and second
trial will be 10 min as planned.
2.3.4
Keeping Bees Between Training and Retention Tests
Depending on the experiment and thus on the question raised, bees may need to be
tested to assess the presence of memory from a few minutes to several days after
training. If you are planning to take several hours between conditioning trials and
memory retention test, keep the bees in a dark, humid container at room temperature
until the test to maintain their physical condition.
Bees that have to be tested several days after conditioning will be subjected to
different handling procedures to ensure survival until the respective retention test.
Bees tested 1 day after conditioning can be kept in the harness tubes because mor-
tality is usually low in these conditions; yet, bees should be fed to satiation with
50 % sucrose solution, at least 60 min after the end of conditioning to ensure sur-
vival. Bees tested more than 2 days after conditioning should be kept in small cages
because mortality will increase in prolonged harnessing conditions. To this end,
bees need to be individually identifi ed by means of color marks painted on the tho-
rax with watercolors, following a code that allows later recognition. Bees are then
placed in groups of ~30 individuals in small cages (e.g., 65 × 70 × 25 mm) supplied
with water and a diet of 50 % sucrose and 50 % honey mixture ad libitum. The cages
should be kept in a dark and humid container at room temperature. On the morning
of the test day, bees are transferred from the cages into glass vials, cooled on ice,
and placed again individually in the harness tubes. Retrieval tests are usually per-
formed after 5 h of food deprivation to ensure adequate appetitive motivation.
