Fig. 4. Previous intermediate-term memory (ITM) training augments long-term memory (LTM) retention if LTM training occurs up to 5 h after the final ITM training session. A cohort of 20 naïve snails received ITM training and, as in Fig. 3A, exhibited memory at 3 h: the number of attempted pneumostome openings in session 4 was not significantly different (NSD, P>0.05) from that in session 3. Following this interval, these snails received the LTM training procedure and memory was tested 72 h after the last LTM training session. The LTM training procedure resulted in no further statistically significant decrease in the number of attempted openings: session 4 was not significantly different from session 6 (P>0.05). Memory was present when tested 72 h later because the memory test (MT) was not significantly different from session 6 (NSD, P>0.05), but was significantly different from session 1 (P<0.01). (B) As in A, except that the LTM training procedure was initiated 5 h after the last ITM training session. Note that there was a significant difference between the response in session 3 and that in session 4 (P<0.01), indicating that there was no ITM. Memory was present when tested 72 h later because MT was not significantly different from session 6 (NSD, P>0.05), but was significantly different from session 1 (P<0.01). (C) As in A, except that the LTM training procedure was initiated 8 h after the last ITM training session. In this group of snails, there was no augmentation of LTM. That is, there was a significant difference between session 6 and MT (P<0.01) but no significant difference between MT and session 1 (NSD, P>0.05), indicating no memory at 72 h. (D) As in C, except that the LTM training procedure was initiated 24 h after the last ITM training session. Again, there was no augmentation of LTM. There was a significant difference between session 6 and MT (P<0.01) but no significant difference between MT and session 1 (NSD, P>0.05), indicating no memory at 72 h.
