Fig. 6. Preventing RPeD1 impulse activity in operantly conditioned preparations augmented the formation of long-term memory. (A) Upon completion of session 1 in conditioned, yoked, and naïve control preparations, RPeD1 was penetrated with a microelectrode followed by the immediate injection of hyperpolarizing current to prevent impulse activity for up to 20 min. (B) Sample recordings in which RPeD1 impulse activity was prevented after the completion of training session 1 (arrowheads denote the time of hyperpolarizing current injection in B and C). (C) Conditioned preparations significantly reduced their number of attempted pneumostome openings between sessions 1 and 2 (learning; t=4.014, P<0.001) and session 1 and the memory test 18 h later (LTM; t=4.176, P<0.001). Naïve preparations also significantly reduced their pneumostome openings in session 2 (t=3.733, P<0.01), but not in the memory test (t=0.6616, P>0.05) and thus did not show LTM. ^**P<0.01; ^***P<0.001.