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. 2017 May 1;11:80. doi: 10.3389/fnbeh.2017.00080

FIGURE 2.

FIGURE 2

Effects of ISI and ITI lengths, or conditioning cycle numbers on memory retention. (A) Effects of ISI lengths on memory formation. Animals were conditioned with 0.01% 1-nonanol and 160 mM KCl consecutively without an intervening delay (0 s), or 10, 30, 60, or 120 s later with 160 mM KCl after the end of 1-nonanol stimulation by eight-cycle spaced training with a 10-min ITI. Chemotaxis assays were carried out immediately after conditioning. Asterisks (∗p < 0.05, ∗∗p < 0.01) indicate statistically significant differences determined by one-way ANOVA, followed by the Tukey-Kramer test for further comparison with LI values of animals conditioned with ISI (120 s). LIs of animals conditioned with various ISIs were statistically (#p < 0.05, ##p < 0.01) different from the “0” base line when analyzed by using one sample t-test. An equation for calculation of learning index (LI) is also shown, and CIreference is CI of animals treated first with 100% EtOH and then with 160 mM KCl by massed or spaced training unless otherwise stated. Bars are means ± SEM (n = 6–9 assays). (B) ITI effects on memory formation and retention. Animals were conditioned with 0.01% 1-nonanol and 160 mM KCl consecutively without an intervening delay (ISI, 0 s), using eight-cycle spaced training with indicated ITI lengths. Chemotaxis assays were performed immediately (gray bars) or 6 h (open bars) after conditioning. Asterisks (∗∗) indicate statistically significant differences (p < 0.01) determined by one-way ANOVA, followed by the Tukey-Kramer test for further comparison with LIs of animals conditioned without an ITI. LI values were calculated from the equation shown in (A) using CIreference values of animals treated with 100% EtOH and 160 mM KCl. Bars are means ± SEM (n = 6–9 assays). (C) Effects of the number of conditioning cycles on memory formation. Animals were conditioned with 0.01% 1-nonanol and 160 mM KCl consecutively without an intervening delay (ISI, 0 s), using a 10-min ITI and repeating the conditioning 1–11 times. Immediately after conditioning, chemotaxis assays were performed. Asterisks (∗∗) indicate statistically significant differences (p < 0.01) determined by one-way ANOVA, followed by the Tukey-Kramer test for further comparison with LIs of single-conditioned animals. LI values were calculated from the equation shown in (A) using CIreference values of animals treated with 100% EtOH and 160 mM KCl. Bars are means ± SEM (n = 9 assays).