We succeeded in demonstrating that Lymnaea are capable
of the sensory preconditioning by both spaced and
massed training procedures, and showed that the memory
of the conditioning by both training procedures was extinguished
within a few days. Although the spaced training
procedure was first thought to produce large effects on the
conditioned behavior, no significant differences between
these training procedures were found in the sensory preconditioning,
possibly because this conditioning includes a
neutral conditioning CS1–CS2. see Ref. w6x for the de-
tails..