Fig. 7. Crowding does not block intermediate-term memory (ITM). (A) A naïve
cohort of snails (N=46; 23 operantly conditioned and 23 yoked control
snails) was subjected to 1h of crowding immediately after the memory
augmentation procedure and then placed into an uncrowded aquarium for an
additional 1h period. The snails were then tested for memory (MT). That is,
memory was tested 2h after training. A Kruskal–Wallis (non-parametric
ANOVA) was performed on these data (KW=27.726; P<0.01) followed by
a Dunn's Multiple Comparison test. In the cohort that received operant
conditioning training, ITM is present as MT is significantly less than TS
(*P<0.01). These snails were then challenged with a
change-of-context session (CT) 2h later. Memory is not present as CT is not
significantly different from TS (P>0.05). The snails that received
the yoked control procedure (Yoked) do not exhibit ITM (Yoked is not
significantly different from TS; P>0.05). (B) Another cohort of
snails (N=27 operantly conditioned and 27 yoked controls) was crowded
for 24h before the memory augmentation procedure. Following training they were
all placed into an uncrowded aquarium for 2h before the memory test (MT or
Yoked). Data were subjected to a repeated-measures ANOVA
(F53,3=31.651; P<0.01) followed by a
Tukey–Kramer comparison test. Snails that had been operantly conditioned
exhibit ITM when tested (MT; *P<0.01). The yoked
control snails do not exhibit ITM (Yoked not significantly different from TS;
P>0.05). Snails that had received operant conditioning training
were also challenged 2h after MT with a change-of-context test (CT). In CT,
the number of attempted openings was not statistically different than TS
(P>0.05), indicating that snails were not sick. (C) As in B except
snails were only crowded for 1h before the operant conditioning training or
the yoked control procedure. A Kruskal–Wallis (non-parametric ANOVA) was
performed on these data (KW=43.536; P<0.01) followed by a Dunn's
Multiple Comparison test. As in B, ITM is present in the operantly conditioned
snails (MT is significantly different from TS; *P<0.01)
but is not present in the yoked control (Yoked is not significantly different
from TS; P>0.05). Also as in B, when the context was changed,
snails behaved as though they were naïve (i.e. CT is not significantly
different from TS; P>0.05). Values are means ± s.e.m.