In the standard paradigm, Drosophila avoids the heat during training very quickly and stabilizes the arena with the 'cold' pattern orientation in the frontal position, with short excursions into the heated sectors. There is a very prominent behavior to be observed during training: the entering of a reinforced quadrant during training is often followed by a volley of spikes, bringing the fly out of the heat (Fig. 16).
Fig. 16: Typical stretch of yaw torque flight trace during
operant training with volley of spikes as the shutter opens (left arrowhead)
until it closes (right arrowhead). In this trace another spike parameter
modulation can be seen: the spike amplitude is larger in the spikes during
the heat than after the closure of the shutter. Dotted lines denote spike
detection thresholds.
In the classical paradigm, Drosophila is confronted with the contiguity of one pattern orientation paired with heat during training and has no means preventing it from being heated. Observing flies when heated under open loop conditions reveals a behavior very similar to the volley of spikes depicted in Fig. 16: some flies produce spike volleys and a shift in the torque baseline during heating (Fig. 17).
Fig. 17: Stretch of yaw torque flight trace of a single fly
during classical conditioning. The pattern is switched every three seconds.
The torque trace rises high above zero together with the generation of
large, spike-like torque fluctuations whenever the heat is switched on
(arrowheads). The dotted line indicates zero torque.