Conditioning and memory tests are performed on samples of 50 adult
flies (sexes mixed), raised in standard conditions. For all tests
described here, the conditioning procedure consisted of training
sessions separated by 20 min intervals (spaced protocol which
induces long-term memory formation) or immediately following one
another (massed protocol which induces anesthesia-resistant memory
formation only). In the laboratory, the conditioning protocol is now
automatised and allows the simultaneous conditioning of 64 samples.
Conditioning: In each training session flies are first exposed for 60 s
to one odourant simultaneously with a mechanical shock (2000 rpm
vibration pulses of 1 s duration, delivered every 5 s by a test tube
shaker). This period was followed by a 60 s rest period (no odour and
no shock). Then, for 60 s another odourant is delivered, without
shock. The training session ends with a second rest period of 60 s. 3-
octanol and 4-methylcyclohexanol (both 0.6ml/l of paraffin) were
used as odourants.
Memory assay: 15 min (for short-term memory assay) or 24h (for
anesthesia-resistant memory or long-term memory assay) after being
conditioned, the flies are transported to the choice point of a T-maze,
in which they are exposed to two converging currents of air, one
carrying octanol and the other methylcyclohexanol, and allowed to
choose between the two odours for 60s. The memory score is
calculated as the difference in the proportion of individuals choosing
octanol between flies conditioned to avoid methylcyclohexanol and
those conditioned to avoid octanol.