Fig. 4. Crowding, the memory augmentation procedure and LTM formation. Snails (N=52; 26 operantly conditioned, 26 yoked controls) were described in Fig. 3A. (A) Snails that received the operant conditioning procedure were randomly divided into two groups immediately following TS. One group (N=12) was subjected to crowded conditions for 24h, while the other group (N=14) was maintained for 24h in the control, uncrowded conditions. All snails were then tested for memory (MT). The data were subjected to a one-way ANOVA (F_51,4=5.107 P<0.01) followed by a Tukey–Kramer comparison test. As can be seen (B) LTM was not present. That is, the number of attempted openings in MT was not statistically different from TS (P>0.05). (C) By contrast, snails not subjected to crowding exhibited LTM. The number of attempted openings in MT of this group was statistically different from TS (^*P<0.01). Yoked control snails subjected to either crowding or uncrowded conditions showed no statistical difference from TS (P>0.05 for each comparison) nor were they statistically different from each other (P>0.05). Values are means ± s.e.m.