Fig. 6. Crowding before training blocks LTM formation. (A) A naïve cohort of snails (N=56; 28 operantly conditioned and 28 yoked controls) was subjected to 24h of crowding immediately before the memory augmentation procedure. Following training, all snails were placed in an uncrowded aquarium for 24h and then tested for LTM (MT). Data were subjected to a repeated-measures ANOVA (F_55,2=2.378; P>0.05) followed by a Tukey–Kramer comparison test. Neither the operantly conditioned snails nor the yoked control snails exhibited LTM. That is, MT is not significantly different from TS (P>0.05) nor is Yoked different from TS (P>0.05). Finally, Yoked is not significantly different from MT (P>0.05). (B) Crowding for 1h immediately before the memory augmentation procedure is sufficient to block LTM formation. Another naïve cohort of snails (N=19; 10 operantly conditioned and nine yoked controls) was subjected to 1h of crowding immediately before training. Following training, all snails were placed in an uncrowded aquarium for 24h and then tested for LTM (MT). Data were subjected to a repeated-measures ANOVA followed by a Tukey–Kramer comparison test. Neither the operantly conditioned snails nor the yoked control snails exhibit LTM (F_18,2=0.8510; P=0.4364). That is, MT is not significantly different from TS (P>0.05) nor is Yoked different from TS (P>0.05) Finally, Yoked is not significantly different from MT (P>0.05). Values are means ± s.e.m.