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. 2017 Jun 20;11:42. doi: 10.3389/fncir.2017.00042

Figure 1.

Figure 1

Stimulation protocols. Paired and unpaired stimulation protocol. Both protocols were identical except for the training phase. Pre-training (trial 1–3): 10-s-long pulses of the solvent (MO; gray), the olfactory CS (BUT; green), and the control odorant (MCH; blue) were applied. Training (trial 4–9, shaded in gray): each of the six training trials consisted of a 10-s-long CS pulse and four 1.5-s-long 90 V US pulses (electric shock; red). The interval between the onsets of CS and US was 15 s in the paired protocol and 90 s in the unpaired protocol. In the unpaired group, the sequence of CS and US was pseudorandomized. Note that in both groups there was a stimulus-free gap between CS and US. Post-training (trial 10–13): CS, control odorant and US were followed by a last CS presentation at the end of the protocol to detect a possible run-down of calcium signals. The inter-trial interval was 210 s. Calcium imaging was performed during the first 45 s of each trial. Therefore, for the unpaired group only the first stimulus in each trial was recorded. The time of trial onsets is given in minutes. Each protocol lasted 45.5 min.