Locations of the electrode tips in the hippocampus of guinea pigs.

<p>(A) A representative of toluidine blue-stained coronal hippocampus section (30 μm) from a guinea pig that received hippocampal electrical stimulation as the CS. Scale bar represents 1.0 mm; (B, C) Schematic illustration of the locations of all electrode tips. (B) For delay paradigm: (□ group of from Hip-CS (paired) to tone-CS (paired), n = 6; ■ group of from Hip-CS (pseudo-paired) to tone-CS (paired), n = 4; ○ group of from tone-CS (paired) to Hip-CS (paired), n = 7; ● group of from tone-CS (pseudo-paired) to Hip-CS (paired), n = 4); (C) For trace paradigm: (△ group of from Hip-CS (paired) to tone-CS (paired), n = 6; ▲ group of from Hip-CS (pseudo-paired) to tone-CS (paired), n = 4; ◇ group of from tone-CS (paired) to Hip-CS (paired), n = 5; ◆ group of from tone-CS (pseudo-paired) to Hip-CS (paired), n = 4). The coronal brain plates are adapted from the atlas of Rapisarda and Bacchelli [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178502#pone.0178502.ref039" target="_blank">39</a>].</p>