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. Author manuscript; available in PMC: 2016 Jan 1.
Published in final edited form as: Behav Brain Res. 2014 May 23;276:67–75. doi: 10.1016/j.bbr.2014.05.028

Figure 1.

Figure 1

Histograms of USV emission for the 3 different sessions that vary in terms of predictability. A) This session replicated previous work using a variable interval (VI) schedule of trial delivery. Trials came at a VI = 12.5 s and trials included loud tone (PA), PPI (loud tone preceded by soft tone) and PP (soft tone alone). The timing and trial types were unpredictable. USVs rise gradually and then are maintained consistently throughout the session. USVs were seen consistently across all three trial types. B) This session (FI) used a fixed interval (15 s) between each trial. PPI did not change even with high predictability of timing for the trials. USVs were not reduced and slightly increased across all trials. C) Fixed interval and blocked session included highest predictability with 15 s FI along with blocks of trial types. The order of presentation made significant difference. In this example the soft tone trials do not elicit calls since they are at the session start. When at the end, the same PP block does lead to USV calling, as a generalization to the aroused and aversive state the animals have experienced with the repetitive loud tones (modified from Ref. [41]).