Figure 1

(A) Schematic representation of the two-compartment experimental chamber with the preparation. The compartment containing the CNS was continuously perfused with the snail physiological solution. After application of a drop of carrot juice or quinine to the lip it was washed out with the same solution. The neurons, the activity of which was recorded in neurophysiological experiments were: RMtCI. LMtCI, right and left giant meta- cerebral neurons; RPd4, LPd4, right and left pedal serotonergic neurons; RPa2, RPa3, LPa2, LPa3, giant neurons located in both parietal ganglia. (B) Schematic representation of Context 1 and Context 2 in which the snails were trained (shocks in Context 1 only) and tested for tentacle withdrawal amplitude. (C) Example of recordings from 3 functionally different neurons during a pairing trial. Upper trace – recording from a giant parietal (RPa3) premotor interneuron involved in triggering the withdrawal; middle trace – recording from a serotonergic cerebral giant neuron (MtC1) involved in feeding; lower trace – a recording from a serotonergic pedal cell (Pd4) modulating synaptic inputs of parietal premotor neurons. Dotted line shows time of juice application on the lip, dashed line shows time of quinine application on the lip. Notice the lack of response to juice in withdrawal interneuron (upper trace) and pedal serotonergic cell (lower trace), while the feeding interneuron responds both to juice and quinine (middle trace). AB, avoidance behavior and FB, feeding behavior.